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1.
Ying Cui Mingsong Li Elsbeth E. van Soelen Francien Peterse Wolfram M. Kürschner 《Proceedings of the National Academy of Sciences of the United States of America》2021,118(37)
The end-Permian mass extinction event (∼252 Mya) is associated with one of the largest global carbon cycle perturbations in the Phanerozoic and is thought to be triggered by the Siberian Traps volcanism. Sizable carbon isotope excursions (CIEs) have been found at numerous sites around the world, suggesting massive quantities of 13C-depleted CO2 input into the ocean and atmosphere system. The exact magnitude and cause of the CIEs, the pace of CO2 emission, and the total quantity of CO2, however, remain poorly known. Here, we quantify the CO2 emission in an Earth system model based on new compound-specific carbon isotope records from the Finnmark Platform and an astronomically tuned age model. By quantitatively comparing the modeled surface ocean pH and boron isotope pH proxy, a massive (∼36,000 Gt C) and rapid emission (∼5 Gt C yr−1) of largely volcanic CO2 source (∼−15%) is necessary to drive the observed pattern of CIE, the abrupt decline in surface ocean pH, and the extreme global temperature increase. This suggests that the massive amount of greenhouse gases may have pushed the Earth system toward a critical tipping point, beyond which extreme changes in ocean pH and temperature led to irreversible mass extinction. The comparatively amplified CIE observed in higher plant leaf waxes suggests that the surface waters of the Finnmark Platform were likely out of equilibrium with the initial massive centennial-scale release of carbon from the massive Siberian Traps volcanism, supporting the rapidity of carbon injection. Our modeling work reveals that carbon emission pulses are accompanied by organic carbon burial, facilitated by widespread ocean anoxia.The end-Permian mass extinction (EPME) that occurred at 251.941 ± 0.037 Mya is considered the most severe biodiversity loss in Earth history (1, 2). The EPME coincides with the eruption of the Siberian Traps, a voluminous large igneous province (LIP) that occupies 6 million square kilometers (km2) in Siberia, Russia (3–5). The volcanic activity of this LIP is linked to SO2 and CO2 degassing generated by sill intrusion (6–10). The large amount of CO2 injected into the atmosphere is thought to have led to severe global warming (11–14), catastrophic ocean anoxia (15, 16), and extreme ocean and terrestrial acidification (17–21) being lethal for life on land and in the sea (22). To date, no agreement has been reached regarding the source of the 13C-depleted carbon that triggered the global carbon cycle perturbation, the decrease in ocean pH, and the global warming across the EPME. Additionally, atmospheric CO2 levels following the initial pulse of Siberian Traps volcanism and across the EPME remain poorly known (23, 24), limiting our understanding of the climate feedbacks that occur upon greenhouse gas release during this time.To address this critical gap in our knowledge, we constrain the source, pace and total amount of CO2 emissions using an Earth system model of intermediate complexity (i.e., carbon centric-Grid Enabled Integrated Earth system model [cGENIE]; SI Appendix) forced by new astronomically tuned δ13C records from well-preserved lipid biomarkers preserved in sediments from the Finnmark Platform, Norway. The Finnmark Platform is located offshore northern Norway on the Eastern Barents Sea shelf, hosting an expanded shallow marine section (paleo-water depth roughly 50 to 100 m) where two drill cores were collected (7128/12-U-01 and 7129/10-U-01) spanning the Permian–Triassic transition (Fig. 1). A previously generated bulk organic carbon isotope record (δ13Corg) from the same core shows a two-step decline with a total carbon isotope excursion (CIE) magnitude of ∼4‰ (25). Although the sedimentary organic carbon was considered primarily of terrestrial origin, small contributions from marine organic carbon production could not be excluded. Here, we use compound-specific carbon isotope analysis of both long-chain and short-chain n-alkanes preserved in marine sediments in the Finnmark Platform to generate separate yet directly comparable records of δ13C for the terrestrial and the marine realm, respectively, across the EPME. Long-chain n-alkanes with a strong odd-over-even predominance (n-C27 and n-C29) are produced by higher plant leaf waxes, and their isotopic composition (δ13Cwax) relates to their main carbon source (i.e., atmospheric CO2) (26). On the other hand, short-chain alkanes (n-C17 and n-C19) are derived from marine algae, and their δ13C values (δ13Calgae) represent carbon in the marine realm (27, 28). To date, only a few EPME compound-specific carbon isotope studies have been reported, all of which are limited by unfavorable sedimentary facies or high thermal maturity of the organic matter (29, 30). In the present study, the exceptionally low thermal maturity of the organic matter is evident from the yellow color of pollen and spores, indicating a color index 2 out of 7 on the thermal alteration scale of Batten (31), which is equivalent to a vitrinite reflectance R0 of 0.3%. Moreover, the high sedimentation rate (discussed in Carbon Cycle Quantification Using Astrochronology and Earth System Model) of the siliciclastic sediments at the study site allows for studying both marine and terrestrial CIE across the EPME in unprecedented detail. Taken together, the Finnmark sedimentary records enable the reconstruction of individual yet directly comparable carbon isotope records for the terrestrial and the marine realm that can be astronomically tuned and used to quantitatively assess the source, pace, and total amount of 13C-depleted carbon released during the Siberian Traps eruption that led to the EPME. Using our new compound-specific carbon isotope records, rather than marine carbonates, has several advantages: 1) new astrochronology enables a 104-year temporal resolution for our paired marine and terrestrial carbon isotope records; 2) we do not need to assume a constant sedimentation rate between tie point or using diachronous biozones to compare age like those used in global compilations (24) (see Fig. 4A); 3) the δ13Calgae data are not artificially smoothed as in ref. 32 to avoid underestimation of the CIE magnitude; and 4) our records are not affected by dissolution or truncation, a phenomenon common to shallow marine carbonates due to the presumed ocean acidification occurred during the EPME (18, 33). In addition, the directly comparable records of δ13C for the atmosphere and the ocean offer further insights into the size of the true CIE and rate and duration of carbon emissions.Open in a separate windowFig. 1.(A) Paleogeographical map of the Late Permian, with former and current coastlines. Indicated are 1) the location of Finnmark cores 7128/12-U-01 and 7129/10-U-01, 2) the East Greenland site at Kap Stosch discussed in ref. 52, 3) the GSSP site for the base of the Triassic at Meishan, China, and 4) the Kuh-e-Ali Bashi site of Iran (66, 107). The map was modified after ref. 61. (B) Paleogeography and paleobathymetry of the Late Permian used in cGENIE.Open in a separate windowFig. 4.Synthesized proxy records of carbon isotopes from marine carbonates and fossil C3 land plants remains, sea surface temperature, and pH. (A) Comparison between δ13Calgae and global marine carbonate carbon isotopes from sites at Abadeh, Kuh-e-Ali Bashi, Shahreza, and Zal in Iran, Meishan, Wenbudangsang, and Yanggou in South China, at Bálvány North in Hungary, and at Nhi Tao in Vietnam (24). (B) Comparison between δ13Cleaf wax and the δ13C of sedimentary leaf cuticles and wood of C3 land plants from South China (24). (C) Reconstructed sea surface temperature data using conodont fossils (circles) (24) and brachiopods (triangles) (14). The conodont-based temperature data are from sites in the Paleo-Tethys, including Chanakhchi, Kuh-e Ali Bashi, Meishan, Shangsi, and Zal. (D) Relative changes in sea surface pH based on boron isotope proxy from ref. 17 and ref. 20. Pink and red circles are data from scenario 1 and scenario 2 in ref. 17, and green and blue diamonds are data from scenario 1 and scenario 2 in ref. 20. 相似文献
2.
Genomic basis for stimulated respiration by plants growing under elevated carbon dioxide 总被引：1，自引：0，他引：1
Andrew D. B. Leakey Fangxiu Xu Kelly M. Gillespie Justin M. McGrath Elizabeth A. Ainsworth Donald R. Ort 《Proceedings of the National Academy of Sciences of the United States of America》2009,106(9):3597-3602
3.
Ma&#x;gorzata Grzegorczyk-Fra&#x;czak Danuta Barnat-Hunek Wojciech Andrzejuk Jacek Zaburko Monika Zalewska Grzegorz &#x;agd 《Materials》2021,14(8)
The paper presents the experimental studies on the effect of the water containing micro-nano bubbles of various gases on the physico-mechanical properties of lime-cement mortars. In total, 7 types of mortars were prepared: with water containing the micro-nano bubbles of O2, O3 or CO2 as 50% or 100% substitute of ordinary mixing water (tap water) and the reference mortar prepared using tap water. In order to determine the influence of water with micro-nano bubbles of gases, the consistency of fresh mortar and the physical properties of hardened mortar, i.e., specific and apparent density, total porosity, water absorption by weight and capillary absorption, were established. The mechanical strength of the considered mortars was studied as well by conducting the tests for flexural and compressive strengths following 14, 28 and 56 days. Reduced workability and capillary absorption were observed in the modified mortars within the range of 0.9–8.5%. The mortars indicated an increase in the flexural strength after 28 days ranging from 3.4% to 23.5% and improved compressive strength in 1.2–31%, in comparison to the reference mortar. The conducted studies indicated increased flexural and compressive strengths along with the share of micro-nano bubbles of gases in the mixing water. 相似文献
4.
Francesco Conte Ilenia Rossetti Gianguido Ramis Cyril Vaulot Samar Hajjar-Garreau Simona Bennici 《Materials》2022,15(8)
Photo-catalysts based on titanium dioxide, and modified with highly dispersed metallic nanoparticles of Au, Ag, Pd and Pt, either mono- or bi-metallic, have been analyzed by multiple characterization techniques, including XRD, XPS, SEM, EDX, UV-Vis and N2 adsorption/desorption. Mono-metallic photo-catalysts were prepared by wet impregnation, while bi-metallic photocatalysts were obtained via deposition-precipitation (DP). The relationship between the physico-chemical properties and the catalyst’s behavior for various photo-synthetic processes, such as carbon dioxide photo-reduction to liquid products and glucose photo-reforming to hydrogen have been investigated. Among the tested materials, the catalysts containing platinum alone (i.e., 0.1 mol% Pt/TiO2) or bi-metallic gold-containing materials (e.g., 1 wt% (AuxAgy)/TiO2 and 1 wt% (AuxPtz)/TiO2) showed the highest activity, presenting the best results in terms of productivity and conversion for both applications. The textural, structural and morphological properties of the different samples being very similar, the main parameters to improve performance were function of the metal as electron sink, together with optoelectronic properties. The high activity in both applications was related to the low band gap, that allows harvesting more energy from a polychromatic light source with respect to the bare TiO2. Overall, high selectivity and productivity were achieved with respect to most literature data. 相似文献
5.
Mikael K. Sejr Annette Bruhn Tage Dalsgaard Thomas Juul-Pedersen Colin A. Stedmon Martin Blicher Lorenz Meire Kenneth D. Mankoff Jakob Thyrring 《Proceedings of the National Academy of Sciences of the United States of America》2022,119(52)
Global warming accelerates melting of glaciers and increases the supply of meltwater and associated inorganic particles, nutrients, and organic matter to adjacent coastal seas, but the ecosystem impact is poorly resolved and quantified. When meltwater is delivered by glacial rivers, the potential impact could be a reduction in light and nutrient availability for primary producers while supplying allochthonous carbon for heterotrophic processes, thereby tipping the net community metabolism toward heterotrophy. To test this hypothesis, we determined physical and biogeochemical parameters along a 110-km fjord transect in NE Greenland fjord, impacted by glacial meltwater from the Greenland Ice Sheet. The meltwater is delivered from glacier-fed river outlets in the inner parts of the fjord, creating a gradient in salinity and turbidity. The planktonic primary production was low, 20–45 mg C m−2 d−1, in the more turbid inner half of the fjord, increasing 10-fold to around 350 mg C m−2 d−1 in the shelf waters outside the fjord. Plankton community metabolism was measured at three stations, which displayed a transition from net heterotrophy in the inner fjord to net autotrophy in the coastal shelf waters. Respiration was significantly correlated to turbidity, with a 10-fold increase in the inner turbid part of the fjord. We estimated the changes in meltwater input and sea ice coverage in the area for the last 60 y. The long-term trend and the observed effects demonstrated the importance of freshwater runoff as a key driver of coastal ecosystem change in the Arctic with potential negative consequences for coastal productivity.Increasing temperatures induce melting of the Arctic cryosphere including permafrost, glaciers, and sea ice. Combined with increased precipitation, it leads to increased fluxes of freshwater and associated terrigenous material, including organic matter and nutrients (1–3). The combination of warming and freshening has the potential to increase the degree of stratification in open and coastal waters and is hereby expected to impact the status of marine ecosystems. Freshening is especially relevant in the coastal waters around Greenland where the mass loss of the Greenland ice sheet has increased sixfold compared to the 1980s (4), and the downstream effects of high-latitude freshening have been documented (5). The ecosystem consequences of increasing input of freshwater to the Arctic seas in general and the Greenland fjords in particular are poorly quantified. Arctic freshening is a complex process impacting physical and biogeochemical properties and resulting in a broad range of interconnected impacts to biota, making the cumulative impacts on the ecosystems difficult to predict. In the open ocean, a key impact of freshening is increased stratification which may limit nutrient replenishment to the photic zone during postbloom conditions as has been observed in the Canada Basin (6). Freshening is also associated with a decrease in nutrient concentration in surface layers of the central Arctic Ocean (7), increased prokaryote production (8), and a shift in primary producers toward a dominance of picophytoplankton (9). On a more local scale, the freshwater entering Greenland fjords is known to create distinct physical conditions in the inner fjords resulting in biogeochemical gradients (10), inducing physiological stress in residing organisms, and changes in pelagic and benthic community composition (11, 12). As for coastal ecosystems in general, the impact of freshwater depends on local conditions such as catchment area and characteristics, bathymetry (sill depth in particular), and tidal mixing (13). However, a defining characteristic of fjords with marine-terminating glaciers is that part of freshwater supply can be delivered as subglacial discharge and enter the fjord at depth. This results in a freshwater plume rising toward the surface, potentially maintaining a flux of nutrients from bottom waters to the photic zone (14). This has been shown to be important for some productive fjord systems in Greenland (15). In contrast, fjords with land-terminating glaciers, where freshwater is delivered at the fjord surface by rivers, can be highly turbid and stratified, resulting in poor light and nutrient availability and as a consequence, less productivity (16). In addition, glacial meltwater contains bioavailable organic carbon and nutrients which have been speculated to be important for coastal carbon cycling in both Greenland and Alaskan waters (17–19). The Arctic region in general is characterized by terrestrial input of carbon from several large rivers supplying allochthonous carbon from land to coastal regions. Further release of large stores of carbon from the surrounding land may have the potential to alter the Arctic Ocean from a CO2 sink to a source in future (20). The net effect of Greenlandic fjords on regional carbon budgets is currently unknown. Along Greenlands extensive coastline, there is a large number of fjords with variable impacts of meltwater, glaciers, and tidal exchange. In addition to this, it is unclear how changing conditions are influencing the biogeochemistry and as a consequence, the biological productivity. Studies from Siberian coastal waters with extensive input of terrestrial carbon show that mineralization of terrigenous organic matter maintains a net heterotrophic system, releasing CO2 to the atmosphere (21). In general, fjords in West Greenland are productive with tidal mixing and marine-terminating glaciers, supporting vertical mixing of nutrients (15). Here, fjords are essentially autotrophic for most of the year and function as a sink for atmospheric CO2 (22, 23). For these systems, the concentrations of the bioavailable dissolved organic carbon (DOC) in the local rivers can be significantly lower than those reported for Alaskan glaciers (17) and also lower than concentrations generally found in fjord waters (24), suggesting the allochthonous input to be low. The situation could be different in East Greenland fjords, such as Young Sound. It receives 0.63–1.57 km3 of freshwater annually from melting sea ice, land-terminating glaciers, and seasonal precipitation in its catchment (25). During the ice-free period (mid-July to mid-October), the fjord is highly stratified and the primary production in the outer fjord is limited to 10 mg C m−2 y−1 (26). Sediment trap measurements indicate that the majority of particulate organic carbon (POC) reaching the sea floor may be of terrestrial origin (27). The short growth season, low nutrient concentrations, and weak vertical mixing combined with river input make this fjord a site where allochthonous carbon in general and carbon related to glacial meltwater in particular could be important. The aim of this study was to investigate how glacial and terrestrial meltwater may influence coastal pelagic carbon cycling and the potential for uptake of atmospheric CO2 using a unique suite of seasonal measurements along a 120-km transect extending through Young Sound and onto the shelf of the NE Greenland coast. 相似文献
6.
7.
We investigate mechanical, structural and electronic properties of CO2 adsorbed graphitic carbon nitride (g-C3N4) system under biaxial tensile strain via first-principles calculations. The results show that the stress of CO2 adsorbed g-C3N4 system increases and then decreases linearly with the increasing biaxial strain, reaching maximum at 0.12 strain. This is primarily caused by the plane N–C stretching of the g-C3N4. Furthermore, both the Perdew-Burke-Ernzerhof (PBE) and Heyd- Scuseria-Ernzerhof screened hybrid functional (HSE06) band gaps show direct-indirect transitions under biaxial tensile strain and have the maximum also at 0.12 strain. It is found that there is large dipole transition matrix element around Γ point, leading high optical absorption coefficients of the deformed adsorption system, which would be of great use for the applications of new elastic nanoelectronic and optoelectronic devices. 相似文献
8.
To prevent drastic climate change due to global warming, it is necessary to transition to a carbon-neutral society by reducing greenhouse gas emissions in all industrial sectors. This study aims to prepare measures to reduce the greenhouse gas in the cement industry, which is a large source of greenhouse gas emissions. The research uses supercritical CO2 carbonation to develop a carbon utilization fixation technology that uses concrete slurry water generated via concrete production as a new CO2 fixation source. Experiments were conducted using this concrete slurry water and supernatant water under different conditions of temperature (40 and 80 °C), pressure (100 and 150 bar), and reaction time (10 and 30 min). The results showed that reaction for 10 min was sufficient for complete carbonation at a sludge solids content of 5%. However, reaction products of supernatant water could not be identified due to the presence of Ca(HCO3)2 as an aqueous solution, warranting further research. 相似文献
9.
Jibin Fan Yimeng Shi Hongxia Liu Shulong Wang Lijun Luan Li Duan Yan Zhang Xing Wei 《Materials》2022,15(5)
Due to the chemically inert surface of MoS2, uniform deposition of ultrathin high-κ dielectric using atomic layer deposition (ALD) is difficult. However, this is crucial for the fabrication of field-effect transistors (FETs). In this work, the atomic layer deposition growth of sub-5 nm La2O3/Al2O3 nanolaminates on MoS2 using different oxidants (H2O and O3) was investigated. To improve the deposition, the effects of ultraviolet ozone treatment on MoS2 surface are also evaluated. It is found that the physical properties and electrical characteristics of La2O3/Al2O3 nanolaminates change greatly for different oxidants and treatment processes. These changes are found to be associated with the residual of metal carbide caused by the insufficient interface reactions. Ultraviolet ozone pretreatment can substantially improve the initial growth of sub-5 nm H2O-based or O3-based La2O3/Al2O3 nanolaminates, resulting in a reduction of residual metal carbide. All results indicate that O3-based La2O3/Al2O3 nanolaminates on MoS2 with ultraviolet ozone treatment yielded good electrical performance with low leakage current and no leakage dot, revealing a straightforward approach for realizing sub-5 nm uniform La2O3/Al2O3 nanolaminates on MoS2. 相似文献
10.
11.
Alexander H. Bork Margarita Rekhtina Elena Willinger Pedro Castro-Fernndez Jakub Drnec Paula M. Abdala Christoph R. Müller 《Proceedings of the National Academy of Sciences of the United States of America》2021,118(26)
The addition of molten alkali metal salts drastically accelerates the kinetics of CO2 capture by MgO through the formation of MgCO3. However, the growth mechanism, the nature of MgCO3 formation, and the exact role of the molten alkali metal salts on the CO2 capture process remain elusive, holding back the development of more-effective MgO-based CO2 sorbents. Here, we unveil the growth mechanism of MgCO3 under practically relevant conditions using a well-defined, yet representative, model system that is a MgO(100) single crystal coated with NaNO3. The model system is interrogated by in situ X-ray reflectometry coupled with grazing incidence X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. When bare MgO(100) is exposed to a flow of CO2, a noncrystalline surface carbonate layer of ca. 7-Å thickness forms. In contrast, when MgO(100) is coated with NaNO3, MgCO3 crystals nucleate and grow. These crystals have a preferential orientation with respect to the MgO(100) substrate, and form at the interface between MgO(100) and the molten NaNO3. MgCO3 grows epitaxially with respect to MgO(100), and the lattice mismatch between MgCO3 and MgO is relaxed through lattice misfit dislocations. Pyramid-shaped pits on the surface of MgO, in proximity to and below the MgCO3 crystals, point to the etching of surface MgO, providing dissolved [Mg2+…O2–] ionic pairs for MgCO3 growth. Our studies highlight the importance of combining X-rays and electron microscopy techniques to provide atomic to micrometer scale insight into the changes occurring at complex interfaces under reactive conditions.Global concerns about the rising level of greenhouse gas emissions and the associated climate change require the development of efficient processes to remove CO2 selectively from large point sources or directly from the atmosphere. Such processes are termed carbon dioxide capture and storage (CCS) (1) and can be implemented on the industrial scale in different configurations such as precombustion, postcombustion, or oxy-combustion CCS (2, 3). A large variety of both liquid and solid sorbent materials have been explored for CCS, with solid CO2 sorbents being particularly interesting owing to their ability to capture large quantities of CO2 from point sources with, compared to amines, favorable efficiency and cost penalty estimates (4). Yet, the development of inexpensive solid sorbents that capture CO2 with fast rates, possess a high CO2 capacity, and operate with high stability over many CO2 capture and regeneration cycles remains a key challenge. To advance the current state of sorbent design in a rational fashion, an improvement of our current understanding of the interplay between a sorbent’s structural features and its CO2 capture characteristics is required.Magnesium oxide (MgO) is an attractive solid CO2 sorbent, in particular for precombustion CCS applications, that stands out owing to its high theoretical CO2 uptake of 1.09 gCO2⋅gMgO–1 (24.8 mmolCO2⋅gMgO−1) and relatively low temperature for regeneration, as compared to other solid sorbents (e.g., CaO, Li4SiO4, and Li2ZrO3). Despite its high theoretical CO2 capacity, bare MgO displays very sluggish carbonation kinetics, yielding an experimental CO2 uptake of only 0.02 gCO2⋅gMgO–1 after 1 h of exposure to CO2 (5, 6). The low practically obtained CO2 uptake compared to the high theoretical value has been attributed to the high lattice enthalpy of MgO reducing the kinetics of its reaction with CO2 appreciably and to the formation of a monodentate carbonate layer on the surface of MgO, which acts as a CO2-impermeable barrier hampering the further conversion of unreacted MgO (7–9). Encouragingly, the slow uptake of MgO can be accelerated appreciably through an engineering solution, that is, the addition of alkali metal salts (AMS; e.g., NaNO3, KNO3, LiNO3, and their eutectic mixtures) which are molten at operating conditions (10–14). By optimizing the loading of AMS (ca. 20 wt. % AMS), the CO2 uptake of MgO can be increased by a factor of 15 (0.31 gCO2⋅gsorbent–1) compared to unpromoted MgO at identical carbonation durations (13). The kinetics and stability of AMS-promoted MgO can be improved even further when adding alkali earth carbonates such as SrCO3 or CaCO3, which have been hypothesized to act as nucleation seeds or to lead to the formation of double carbonate phases that form with faster kinetics. For such systems, CO2 uptakes of up to 0.65 gCO2⋅gsorbent–1 after 50 carbonation and calcination cycles have been reported (15–17).Owing to the impressive effect of molten AMS on the CO2 uptake of bare MgO, the elucidation of the underlying promoting mechanism(s) has been the aim of a series of studies that have led to the postulation of a number of working hypotheses (12, 13, 16, 18–22). For example, combining thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and powder X-ray diffraction (XRD), it has been proposed that the addition of AMS promotes the CO2 uptake of MgO through the following two effects. Firstly, it has been argued that AMS prevent the formation of a CO2-impermeable monodentate carbonate layer on the surface of MgO, and they dissolve CO2 that reacts with oxide ions (O2–) in the nitrate (23), leading to the formation of reactive carbonate ions (CO32–) that subsequently react with Mg2+ to form MgCO3 (13). A second hypothesis, based on TGA and density functional theory (DFT) calculations, has argued that the promoting role of the AMS is mainly due to the molten salt’s ability to lower the energy barrier associated with the high lattice enthalpy of MgO by dissolving the solid metal oxide (12, 18). The dissolution of MgO in the molten promoter yields solvated [Mg2+…O2–] ionic pairs that have weaker bonds compared to the strong ionic bonds in bulk MgO (12). The DFT calculations showed that the rate-controlling step for the reaction between CO2 and MgO is the activation of the MgO ionic bond; the energy barrier to form [Mg2+…O2–] ionic pairs in the molten NaNO3 is 5.33 eV, compared to 7.07 eV without NaNO3 (12). The dissolved ionic pair reacts with CO2 that is adsorbed on the MgO surface, that is, at the triple phase boundary (TPB) between MgO, CO2, and the molten phases, to form [Mg2+…CO32–] ionic pairs. Upon reaching saturation, the [Mg2+…CO32–] ionic pairs precipitate as a crystalline MgCO3 phase. It is further argued that the carbonate may precipitate away from the original dissolution site so as to not prohibit further reaction. Following this argument, the reaction would, in theory, continue until MgO is completely converted. However, in practice, MgO conversion stops at ∼70%, which has been argued to arise from a reducing TPB length. A recent in situ total scattering study points to a more multifaceted role of the AMS promoter in the MgO−CO2 system, as the AMS do not affect only the nucleation of MgCO3 but also the microstructure and growth of the MgCO3 formed (20).Turning to the kinetics of CO2 absorption, TGA-based studies of NaNO3-promoted MgO powders have shown that the formation of MgCO3 is characterized by a nucleation and growth process (16). The characteristic sigmoidal kinetic curve of MgO conversion suggests that the carbonate formation is “autocatalytic”; that is, once a stable nucleation seed is formed, the growth rate is accelerated. This interpretation was corroborated by experimental evidence that showed that the induction period, that is, the time required for the first stable nuclei to form, can be shortened by the inclusion of “inert” SrCO3 seeds, which act as nucleation sites for MgCO3 (16). Although there is a general agreement on the nucleation- and growth-based mechanism for the formation of MgCO3, there are competing hypotheses on the nature of magnesium carbonate formation, that is, where it forms (at the interface AMS/MgO, at the TPB, or inside the AMS), its growth habit, and its morphology. According to an in situ TEM study of MgO nanoparticles that were physically mixed with a eutectic mixture of AMS, MgCO3 nucleates favorably at the TPB (24, 25). Nonetheless, a different study suggests that the TPB is not a necessary condition for the absorption to take place, as carbonates (MgCO3) were detected on the surface of a MgO(100) single crystal that was covered completely by NaNO3 and treated under CO2 (330 °C), as revealed by ex situ FTIR after the removal of NaNO3 (16). Jo et al. (16) proposed that MgCO3 is formed inside the molten promoter through nucleation and growth steps.Hence, despite extensive efforts, the mechanisms behind the promoting role of AMS on MgO-based CO2 sorbents have not been unveiled yet. Atomic-level insight into the promoting effect of AMS would allow unlocking of the full potential of MgO-based CO2 sorbents and design materials that approach (repeatedly) full conversion over a large number of CO2 capture and regeneration cycles. To obtain such atomic-level insight, well-defined model systems and interrogation of them with detailed (in situ) characterization techniques are required. In this study, we utilize a single-crystal MgO(100) surface [the most stable and abundant MgO facet (21, 26, 27)] coated with NaNO3 and probe, in detail, its structural dynamics under CO2 capture conditions. Synchrotron-based, in situ X-ray reflectometry (XRR) and grazing incidence XRD (GIXRD) unravel the changes occurring at the surface of MgO under CO2 capture condition (allowing study of the buried interface between the NaNO3 promoter and MgO). We complemented the in situ X-ray−based characterizations by (ex situ) scanning electron microscopy (SEM) to characterize, in detail, the morphology of the MgCO3 product formed (after carbonation and after removing the NaNO3 promoter). Our studies evidence the formation of a noncrystalline carbonate layer on bare MgO(100) under CO2 capture conditions. In contrast, MgO(100) coated with NaNO3 exhibited an island-type growth of MgCO3, as opposed to a homogeneous surface layer growth. MgCO3 grows in a highly oriented fashion with a sectored-plate habit growth at the interface between NaNO3/MgO(100), following a nucleation and growth mechanism. High-resolution TEM (HRTEM) provided atomic-level insight into the MgCO3/MgO interface, evidencing an epitaxial arrangement between MgCO3 and MgO whereby the lattice mismatch between MgCO3 and MgO is relaxed through lattice misfit dislocations. 相似文献
12.
Rohit Philip Thomas Simon Viniol Alexander Marc Knig Irene Portig Zaher Swaid Andreas H. Mahnken 《Medicine》2021,100(2)
Carbon dioxide (CO2) gas is an established alternative to iodine contrast during angiography in patients with risk of postcontrast acute kidney injury and in those with history of iodine contrast allergy. Different CO2 delivery systems during angiography are reported in literature, with automated delivery system being the latest. The aim of this study is to evaluate the safety, efficacy, and learning curve of an automated CO2 injection system with controlled pressures in peripheral arterial interventions and also to study the patients’ tolerance to the system.From January 2018 to October 2019 peripheral arterial interventions were performed in 40 patients (median age-78 years, interquartile range: 69–84 years) using an automated CO2 injection system with customized protocols, with conventional iodine contrast agent used only as a bailout option. The pain and tolerance during the CO2 angiography were evaluated with a visual analog scale at the end of each procedure. The amount of CO2, iodine contrast used, and radiation dose area product for the interventions were also systematically recorded for all procedures. These values were statistically compared in 2 groups, viz first 20 patients where a learning curve was expected vs the rest 20 patients.All procedures were successfully completed without complications. All patients tolerated the CO2 angiography with a median total pain score of 3 (interquartile range: 3–4), with no statistical difference between the groups (P = .529). The 2 groups were statistically comparable in terms of comorbidities and the type of procedures performed (P = .807). The amount of iodine contrast agent used (24.60 ± 6.44 ml vs 32.70 ± 8.70 ml, P = .006) and the radiation dose area product associated were significantly lower in the second group (2160.74 ± 1181.52 μGym2 vs 1531.62 ± 536.47 μGym2, P = .043).Automated CO2 angiography is technically feasible and safe for peripheral arterial interventions and is well tolerated by the patients. With the interventionalist becoming familiar with the technique, better diagnostic accuracy could be obtained using lower volumes of conventional iodine contrast agents and reduction of the radiation dose involved. 相似文献
13.
Andri Isak Thorhallsson Francesco Fanicchia Emily Davison Shiladitya Paul Svava Davidsdottir Dagur Ingi Olafsson 《Materials》2021,14(11)
Geothermal process equipment and accessories are usually manufactured from low-alloy steels which offer affordability but increase the susceptibility of the materials to corrosion. Applying erosion-corrosion-resistant coatings to these components could represent an economical solution to the problem. In this work, testing of two newly developed laser metal deposited high-entropy alloy (LMD-HEA) coatings—CoCrFeNiMo0.85 and Al0.5CoCrFeNi, applied to carbon and stainless steels—was carried out at the Hellisheidi geothermal power plant. Tests in three different geothermal environments were performed at the Hellisheidi site: wellhead test at 194 °C and 14 bar, erosion test at 198 °C and 15 bar, and aerated test at 90 °C and 1 bar. Post-test microstructural characterization was performed via Scanning Eletron Microscope (SEM), Back-Scattered Electrons analysis (BSE), Energy Dispersive X-ray Spectroscopy (EDS), optical microscopy, and optical profilometry while erosion assessment was carried out using an image and chemical analysis. Both the CoCrFeNiMo0.85 and Al0.5CoCrFeNi coatings showed manufacturing defects (cracks) and were prone to corrosion damage. Results show that damage in the CoCrFeNiMo0.85-coated carbon steel can be induced by manufacturing defects in the coating. This was further confirmed by the excellent corrosion resistance performance of the CoCrFeNiMo0.85 coating deposited onto stainless steel, where no manufacturing cracks were observed. 相似文献
14.
{001}TiO2/TiOF2 photocatalytic composites with a high activity {001} crystal plane were prepared by one-step hydrothermal methods using butyl titanate as a titanium source and hydrofluoric acid as a fluorine source. X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), raman spectroscopy, N2 adsorption-desorption curve (BET), UV-Vis diffuse absorption spectroscopy (UV-Vis DRS), X-ray photoelectron spectroscopy (XPS), and fluorescence spectroscopy (PL) were used to evaluate the structure, morphology, specific surface area, optical properties, and photocarrier separation ability of {001}TiO2/TiOF2. Ammonia nitrogen was taken as the target pollutant, and the degradation performance of the catalyst was investigated. The results show that hydrofluoric acid improves the content of {001} crystal plane of TiO2 with high activity; it also improves the specific surface area and dispersion of the composite material and adjusts the ratio of {001}TiO2 to TiOF2 in the composite material to enhance the absorption capacity of the composite material and reduce the band gap width of the composite material. The degradation rate of ammonia nitrogen by 100 mg F15 is 93.19% when the initial concentration of ammonia nitrogen is 100 mg/L and pH is 10. Throughout the reaction process, the {001}TiO2/TiOF2 composite produces superoxide anion radical (·O2−) and hydroxyl radical (·OH) to oxidize NH3·H2O and generate N2 accompanied by a small amount of NO3− and NO2−. 相似文献
15.
16.
Jia Xing Xi Lu Shuxiao Wang Tong Wang Dian Ding Sha Yu Drew Shindell Yang Ou Lidia Morawska Siwei Li Lu Ren Yuqiang Zhang Dan Loughlin Haotian Zheng Bin Zhao Shuchang Liu Kirk R. Smith Jiming Hao 《Proceedings of the National Academy of Sciences of the United States of America》2020,117(47):29535
China is challenged with the simultaneous goals of improving air quality and mitigating climate change. The “Beautiful China” strategy, launched by the Chinese government in 2020, requires that all cities in China attain 35 μg/m3 or below for annual mean concentration of PM2.5 (particulate matter with aerodynamic diameter less than 2.5 μm) by 2035. Meanwhile, China adopts a portfolio of low-carbon policies to meet its Nationally Determined Contribution (NDC) pledged in the Paris Agreement. Previous studies demonstrated the cobenefits to air pollution reduction from implementing low-carbon energy policies. Pathways for China to achieve dual targets of both air quality and CO2 mitigation, however, have not been comprehensively explored. Here, we couple an integrated assessment model and an air quality model to evaluate air quality in China through 2035 under the NDC scenario and an alternative scenario (Co-Benefit Energy [CBE]) with enhanced low-carbon policies. Results indicate that some Chinese cities cannot meet the PM2.5 target under the NDC scenario by 2035, even with the strictest end-of-pipe controls. Achieving the air quality target would require further reduction in emissions of multiple air pollutants by 6 to 32%, driving additional 22% reduction in CO2 emissions relative to the NDC scenario. Results show that the incremental health benefit from improved air quality of CBE exceeds 8 times the additional costs of CO2 mitigation, attributed particularly to the cost-effective reduction in household PM2.5 exposure. The additional low-carbon energy polices required for China’s air quality targets would lay an important foundation for its deep decarbonization aligned with the 2 °C global temperature target.China is facing serious air pollution problems, particularly for ambient PM2.5 (particulate matter with aerodynamic diameter less than 2.5 μm) which has harmful effects on human health (1–3). To protect human health, strengthened air pollution control policies were recently implemented in China targeting 35 μg⋅m−3 or less for all cities by 2035 (4). The Action Plan on Prevention and Control of Air Pollution, released in 2013, has resulted in noticeable reductions in urban ambient PM2.5 concentrations (5, 6). In 2018, however, China’s national PM2.5 standard of 35 μg⋅m−3 annual average was exceeded in 217 of China’s 338 cities at the prefecture or higher level, not to mention exceedance of the World Health Organization (WHO) guideline (annual mean PM2.5 concentration <10 μg⋅m−3). A big challenge for future improvement is that advanced end-of-pipe control technologies have already been widely applied in electric and industrial sectors (7, 8). For example, over 90% of coal-fired power plants had installed end-of-pipe control technologies by 2018 (8). Therefore, the potential for further reductions using end-of-pipe control measures might be limited, and implementation of low-carbon energy policies to constrain total energy consumption and promote a transition to clean energy is expected to be an inevitable option for further reducing air pollution (9).The impacts of climate change on humans and ecosystems have also received considerable attention in China over the past few decades, and strategies for mitigating these impacts have been adopted (10). In 2016, China officially signed its Nationally Determined Contribution (NDC) in the Paris Commitment, which pledges for CO2 emissions per unit of GDP in 2030 to fall by 60 to 65% compared to 2005. A big concern arises as to whether China will continue its carbon reduction even under a pessimistic international situation after the US withdrawal from the Paris Agreement in 2019. Previous studies (11–18) have suggested that climate mitigation-oriented low-carbon energy policies can result in a reduction in air pollution.Therefore, there is a question as to whether China needs the application of low-carbon energy technologies and fuels to meet its air quality target. Such synergy is important, since many developing countries (e.g., China, India) are currently experiencing serious air pollution problems, and reducing air pollution is typically a more pressing national concern than climate mitigation (19). This could lead to continuous reductions in CO2 emissions even under a pessimistic international situation for mitigating climate change.Here, we project future air quality attainment in China through 2035, assess the CO2 reduction cobenefits associated with attaining the ambient PM2.5 standards, and evaluate the health and climate impacts associated with air quality attainment-oriented energy policies. We accomplish this by coupling an integrated assessment model [GCAM, the Global Climate Assessment Model (20)], tuned with a detailed bottom-up emission inventory (21), and an air quality model [CMAQ, the Community Multiscale Air Quality model (22)] to evaluate future air quality and CO2 emissions, and an integrated exposure−response (IER) model to evaluate the health effects due to the long-term ambient O3 and both ambient and household PM2.5 exposures in China. This integrated approach captures the nonlinearities among energy, emissions, concentrations, and health, thus allowing us to assess the cobenefits of air quality attainment on protecting health and mitigating CO2 in an internally consistent framework.This study investigates future emissions of air pollutants and CO2 in China under three future pathways with different considerations of two energy scenarios and two end-of-pipe control levels (Table 1). We first designed the NDC−current legislation (CLE) pathway to represent the CO2 intensity reduction targets outlined by China’s NDC to meet the Paris Commitment (23), with CLE level of end-of-pipe controls. This pathway represents the current ongoing energy policies and end-of-pipe control measures to be conducted in China following CLE. For the purpose of air quality attainment, we first designed the NDC−maximum feasible reduction (MFR) pathway to represent the same ongoing energy policies as the NDC−CLE scenario, but with MFR level realized by end-of-pipe controls. Additionally, to achieve the air quality attainment in 2035, we also introduce the CBE−MFR pathway, in which low-carbon energy policies beyond the NDC requirements are implemented (i.e., the cobenefit energy scenario [CBE]) with the MFR level of end-of-pipe controls.Table 1.Design of future projection of air pollutant and CO2 emissions
Open in a separate window*The NDC scenario refers to the CLE of energy policies and plans conducted in China. Such an NDC scenario has a relatively conservative CO2 target, as it only requires a peak in CO2 emissions before 2030 and this has already been implemented in current Chinese plans. Following Fawcett et al. (23), we set the CO2 emissions to peak in 2030 at about 12 Gt (excluding agriculture and land use) and decrease by 4.5% every 5 y after 2030.†At the CLE level, we assume that only the currently existing control policies are in place, including the Three-Year Action Plan for Winning the Blue Sky War from 2018 to 2020 and the 13th Five-Year Plan during 2015–2020. For example, the ultralow emission standard will be applied for all existing coal-fired units nationwide, and newly built coal-fired units in eastern China will be required to have emission rates equivalent to those of gas-fired units (SI Appendix, Text S6). Furthermore, the ultralow emission standard will be implemented for key industries, including iron and steel, cement, plate glass, coking, nonferrous metal, and bricks (SI Appendix, Text S7). Strengthened emission standards are also applied to the transportation sector, reducing total emissions from the transport fleet despite growing travel demand (SI Appendix, Text S8). Advanced, low-emissions stoves will replace traditional household coal and biomass heating and cooking stoves in the commercial and household sector (SI Appendix, Text S9).‡At the MFR level, all of the feasible control policies will be applied to realize the maximal application of end-of-pipe controls. For example, desulfurization and denitrification efficiencies in coal-fired power plants reach their highest levels (99.0% and 91.5%, respectively) (SI Appendix, Text S6); maximal application rates of advanced desulfurization, denitrification, and dedusting technologies are also applied in the industrial sector (SI Appendix, Text S7); and advanced stoves with low emissions are fully adopted to replace traditional bulk coal and biomass use in the buildings (SI Appendix, Text S9).§The CBE scenario is designed for air quality attainment only, with no further constraints from the long-term climate goals (i.e., to meet the 2 °C global temperature target set out by Paris Agreement).Both energy scenarios are projected under the same future socioeconomic assumptions (SI Appendix, Text S1), and their assumptions about low-carbon energy policies for the industry, building (i.e., residential and commercial), transportation, and electric sectors are detailed in SI Appendix, Texts S2–S5, respectively. As presented in Fig. 1A, the total energy uses in NDC and CBE in 2035 are estimated to be 150 and 126 exajoules (EJ), respectively. These values represent increases of 24% and 4%, respectively, from 2015, driven by the future growth of the economy and population (SI Appendix, Fig. S1). The total CO2 emissions in NDC and CBE are estimated as 11.3 and 8.8 Gt, respectively, in 2035. Two levels of end-of-pipe control are applied to the electricity, industry, transportation, and building and non−energy-related sectors, which are detailed in SI Appendix, Texts S6–S9. The emission factors for PM2.5, NOx (in terms of NO2), and SO2 have been greatly reduced with the application of end-of-pipe controls in 2035, compared to 2015 (Fig. 1B). Note that the removal efficiencies of control technologies are less than 50% for domestic and agricultural sectors, which are difficult to control. The challenge to reducing the future emissions includes the continuous growth of activities (Fig. 1A), as well as limited reduction potentials of end-of-pipe control measures (Fig. 1B). For example, the end-of-pipe controls cannot be feasibly applied to domestic stoves. There are still over 200,000 industrial boilers which cannot be well controlled because current available end-of-pipe control techniques for small boilers have relatively lower SO2 and NOx removal efficiency compared with power plants. In addition, the NMVOCs (nonmethane volatile organic compounds) and NH3 emissions are very hard to control by current available end-of-pipe control technologies.Open in a separate windowFig. 1.The energy consumption in units of exajoules (EJ) and CO2 emissions of two energy scenarios (A) and emission factors in two end-of-pipe control levels (B) compared with that in 2015. 相似文献
| Pathway | Energy scenario | End-of-pipe control levels |
| (1) NDC−CLE | Baseline scenario which considers only CO2 intensity reduction to meet the Paris Commitment* | CLE† |
| (2) NDC−MFR | Same as energy scenario in NDC−CLE. | MFR‡ |
| (3) CBE−MFR | Cobenefit energy scenario with implementation of low carbon policies related to energy conservation (e.g., improvement of energy efficiency)§ | MFR‡ |
17.
Tziperman E Halevy I Johnston DT Knoll AH Schrag DP 《Proceedings of the National Academy of Sciences of the United States of America》2011,108(37):15091-15096
The glaciations of the Neoproterozoic Era (1,000 to 542 MyBP) were preceded by dramatically light C isotopic excursions preserved in preglacial deposits. Standard explanations of these excursions involve remineralization of isotopically light organic matter and imply strong enhancement of atmospheric CO2 greenhouse gas concentration, apparently inconsistent with the glaciations that followed. We examine a scenario in which the isotopic signal, as well as the global glaciation, result from enhanced export of organic matter from the upper ocean into anoxic subsurface waters and sediments. The organic matter undergoes anoxic remineralization at depth via either sulfate- or iron-reducing bacteria. In both cases, this can lead to changes in carbonate alkalinity and dissolved inorganic pool that efficiently lower the atmospheric CO2 concentration, possibly plunging Earth into an ice age. This scenario predicts enhanced deposition of calcium carbonate, the formation of siderite, and an increase in ocean pH, all of which are consistent with recent observations. Late Neoproterozoic diversification of marine eukaryotes may have facilitated the episodic enhancement of export of organic matter from the upper ocean, by causing a greater proportion of organic matter to be partitioned as particulate aggregates that can sink more efficiently, via increased cell size, biomineralization or increased C∶N of eukaryotic phytoplankton. The scenario explains isotopic excursions that are correlated or uncorrelated with snowball initiation, and suggests that increasing atmospheric oxygen concentrations and a progressive oxygenation of the subsurface ocean helped to prevent snowball glaciation on the Phanerozoic Earth. 相似文献
18.
Katherine M. Ratliff Anna E. Braswell Marco Marani 《Proceedings of the National Academy of Sciences of the United States of America》2015,112(51):15580-15584
The elevation and extent of coastal marshes are dictated by the interplay between the rate of relative sea-level rise (RRSLR), surface accretion by inorganic sediment deposition, and organic soil production by plants. These accretion processes respond to changes in local and global forcings, such as sediment delivery to the coast, nutrient concentrations, and atmospheric CO2, but their relative importance for marsh resilience to increasing RRSLR remains unclear. In particular, marshes up-take atmospheric CO2 at high rates, thereby playing a major role in the global carbon cycle, but the morphologic expression of increasing atmospheric CO2 concentration, an imminent aspect of climate change, has not yet been isolated and quantified. Using the available observational literature and a spatially explicit ecomorphodynamic model, we explore marsh responses to increased atmospheric CO2, relative to changes in inorganic sediment availability and elevated nitrogen levels. We find that marsh vegetation response to foreseen elevated atmospheric CO2 is similar in magnitude to the response induced by a varying inorganic sediment concentration, and that it increases the threshold RRSLR initiating marsh submergence by up to 60% in the range of forcings explored. Furthermore, we find that marsh responses are inherently spatially dependent, and cannot be adequately captured through 0-dimensional representations of marsh dynamics. Our results imply that coastal marshes, and the major carbon sink they represent, are significantly more resilient to foreseen climatic changes than previously thought.Coastal marsh extent and morphology are directly controlled by rate of relative sea-level rise (RRSLR) and the soil accretion rate, the latter associated with inorganic sediment deposition and organic soil production by plants. Previous studies observed that CO2 fertilization increases marsh plant biomass productivity through increased water use efficiency and photosynthesis (1), and hypothesized that, as a consequence, marsh resilience should increase via increased organic accretion (2, 3). However, this hypothesis has not yet been tested, and the observed increased plant productivity in response to the CO2 fertilization effect has not been translated into its actual geomorphic effects. In fact, direct CO2 effects on vegetation and marsh accretion (as opposed to its indirect effects, e.g., via the increase in temperature) have not yet been incorporated into marsh models, and their importance relative to other leading forcings of marsh dynamics (e.g., inorganic deposition, RRSLR, nutrient levels) remains unknown. Here we use existing data and a 1D ecomorphodynamic model to assess the direct impacts of elevated CO2 on marsh morphology, relative to ongoing [e.g., RRSLR, and suspended sediment concentration (SSC)] and emerging [nutrient levels (4–6)] environmental change. 相似文献
19.
Ka-Young Chung Kyung-Min Lim Seung-Min Chung Moo-Yeol Lee Ji-Yoon Noh Ok-Nam Bae 《Platelets》2013,24(3):127-133
To investigate shear stress-induced platelet activation, the cone-plate viscometer or the Couette rotational viscometer has been widely used. In a previous report, it was shown that shearing platelet-rich plasma using a Couette rotational viscometer could lead to an increase in pH by CO2 release. However, any clear mechanism has not been provided. In this study, we examined whether shearing cell free plasma only using a cone-plate viscometer can also induce pH increase and studied the underlying mechanism of shear-induced pH increase by directly measuring total CO2 (TCO2) and CO2 tension (PCO2). When human plasma was sheared using a cone-plate viscometer, the pH of the human plasma increased time- and shear rate-dependently. Although TCO2 of human plasma was not affected, PCO2 was decreased by shearing, indicating that the decreased PCO2 is associated with a pH increase of plasma. In addition, the pH of bicarbonate-containing suspension buffer was also shown to be increased by shearing; suggesting that the platelet studies using suspension buffers containing bicarbonate could be affected similarly. The effects of pH changes on shear stress-induced platelet activation were also investigated in the same in vitro systems. While shear stress-induced platelet aggregation was not affected by the pH changes, P-selectin expression was significantly increased in accordance with the pH increase. In conclusion, shear stress using a cone-plate viscometer induces pH increase in plasma or bicarbonate-containing suspension buffer through a PCO2 decrease and the pH changes alone can contribute to platelet activation by enhancing shear stress-induced P-selectin expression. 相似文献
20.
The photocatalytic reduction of carbon dioxide to renewable fuel or other valuable chemicals using solar energy is attracting the interest of researchers because of its great potential to offer a clean fuel alternative and solve global warming problems. Unfortunately, the efficiency of CO2 photocatalytic reduction remains not very high due to the fast recombination of photogenerated electron–hole and small light utilization. Consequently, tremendous efforts have been made to solve these problems, and one possible solution is the use of heterojunction photocatalysts. This review begins with the fundamental aspects of CO2 photocatalytic reduction and the fundamental principles of various heterojunction photocatalysts. In the following part, we discuss using TiO2 heterojunction photocatalysts with other semiconductors, such as C3N4, CeO2, CuO, CdS, MoS2, GaP, CaTiO3 and FeTiO3. Finally, a concise summary and presentation of perspectives in the field of heterojunction photocatalysts are provided. The review covers references in the years 2011–2021. 相似文献