Solar thermochemical CO2 splitting with doped perovskite LaCo0.7Zr0.3O3: thermodynamic performance and solar-to-fuel efficiency

The research of thermochemical CO₂ splitting based on perovskites is a promising approach to green energy development. Performance evaluation was performed towards the doped perovskite LaCo_0.7Zr_0.3O₃ (LCZ-73) based two-step thermochemical CO₂ splitting process thermodynamically based on the experimentally derived parameters for the first time. The impacts of vacuum pump and inert gas purge to reduce oxygen partial pressure and CO₂ heating on the performance parameter η_{solar-to-fuel} have been analyzed. The results showed that at the P_O2 of 10⁻⁵ bar, non-stoichiometric oxygen δ increased by more than 3 times as the reduction temperature varied from 1000 °C to 1300 °C, however, no significant deviation of δ was observed between 1300 °C and 1400 °C. The reaction enthalpy ranged from 60 to 130 kJ mol⁻¹ corresponding to δ = 0.05–0.40. Comparing the abovementioned two ways to reduce the oxygen partial pressure, the η_{solar-to-fuel} of 0.39% and 0.1% can be achieved with 75% and without heat recovery with the CO₂ flow rate of 40 sccm under experimental conditions, respectively. The energy cost for CO₂ heating during the thermodynamic process as the n_CO2/n_LCZ-73 increases was obtained from the perspective of energy analysis. The ratio of n_CO2/n_LCZ-73 at lower temperature required more demanding conditions for the aim of commercialization. Finally, the ability of perovskite to split CO₂ and thermochemical performance were tested under different CO₂ flow rates. The results showed that high CO₂ flow rate was conducive to the production of CO, but at the cost of low η_{solar-to-fuel}. The maximum solar-to-fuel efficiency of 1.36% was achieved experimentally at a CO₂ flow rate of 10 sccm in the oxidation step and 75% heat recovery.

Thermodynamics analysis of two-step thermochemical CO₂ splitting with LaCo_0.7Zr_0.3O₃ with gas–gas, gas–solid phase heat recuperation is performed based on experiment.     

Photoelectrochemical performance of a spin coated TiO2 protected BiVO4-Cu2O thin film tandem cell for unassisted solar water splitting

A tandem cell consisting of a Mo-BiVO₄/TiO₂/FeOOH photoanode–Cu₂O/TiO₂/MoS₂ photocathode was prepared for unassisted solar water splitting. The protective TiO₂ layer was prepared by a cost-effective spin coating technique. The individual Mo-BiVO₄/TiO₂/FeOOH photoanode and the Cu₂O/TiO₂/MoS₂ photocathode yielded a current density of ∼0.81 mA cm⁻² at 1.23 V vs. RHE and ∼−1.88 mA cm⁻² at 0 V vs. RHE, respectively under 100 mW cm⁻² xenon lamp illumination. From the individual photoelectrochemical analysis, we identify the operating points of the tandem cell as 0.66 V vs. RHE and 0.124 mA cm⁻². The positive current density from the operating points proves the possibility of non-zero operation of the tandem cell. Finally, a two-electrode Mo-BiVO₄/TiO₂/FeOOH-Cu₂O/TiO₂/MoS₂ tandem cell was constructed and analysed for unassisted operation. The obtained unassisted current density of the tandem cell was ∼65.3 μA cm⁻² with better stability compared to the bare BiVO₄-Cu₂O tandem cell. The results prove that the spin coated TiO₂ protective layer can be a viable approach to protect the photoelectrodes from photocorrosion with better stability and enhanced photoelectrochemical (PEC) performance.

Mo-BiVO₄/TiO₂/FeOOH photoanode–Cu₂O/TiO₂/MoS₂ photocathode tandem cells with photoelectrochemical stability testing.     

Extracorporeal CO2-removal with a heparin coated artificial lung

Treatment of severe acute respiratory failure with extracorporeal gas exchange necessitating near complete systemic anticoagulation requires a delicate balance to be maintained between disseminated intravascular coagulation and hemorrhagic complications. The present study describes our first experience using a heparin coated extracorporeal artificial lung and circuitry during clinical extracorporeal CO₂ removal. In spite of a partial thromboplastin time and activated clotting time within or close to the normal range, neither laboratory evidence for disseminated intravascular coagulation induced by the extracorporeal circuit nor thrombi in the pulmonary vasculature were found. Scanning electron microscopy of the heparin coated hollow fiber gas exchanger demonstrated only minor deposits on the surface. Use of a heparin coated artificial lung may enhance the margin of safety of extracorporeal gas exchange and ultimately broaden its indications.     

K-doped CeO2–ZrO2 for CO2 thermochemical catalytic splitting

Green syngas production is a sustainable energy-development goal. Thermochemical H₂O/CO₂ splitting is a very promising sustainable technology allowing the production of H₂ and CO with only oxygen as the by-product. CeO₂–ZrO₂ systems are well known thermochemical splitting catalysts, since they combine stability at high temperature with rapid kinetics and redox cyclability. However, redox performances of these materials must be improved to allow their use in large scale plants. K-doped systems show good redox properties and repeatable performances. In this work, we studied the effect of potassium content on the performances of ceria–zirconia for CO₂ splitting. A kinetic model was developed to get insight into the nature of the catalytic sites. Fitting results confirmed the hypothesis about the existence of two types of redox sites in the investigated catalytic systems and their role at different K contents. Moreover, the model was used to predict the influence of key parameters, such as the process conditions.

K-doping enhances redox properties of ceria–zirconia towards thermochemical CO₂ splitting, showing promising performances at about 7 wt% of K.     

采用烧结工艺粘结多孔层植入体多孔层的误解

目的:人们对多孔层植入体多孔层粘结工艺的烧结褒贬不一,都是对它的本质没有深入研究所作的评断.本质:烧结不可以作受力构件的连接,烧结的本质是粘接温度超过基体合金的固相线温度1 230℃以上5℃或更高,造成基体合金产生一系列严重问题.危害:在此温度下,其晶界中的低熔点共晶和脆性的金属间化合物相流淌而出粘接金属小球显著地降低基体合金的疲劳强度,及其与柄表面形成晶界缝隙,扩展成裂纹,是柄折断的根源.讨论:分析柄折断的原因既不是槽口,又不是冶金缺陷,一定是烧结引起的,其依据是烧结温度太高.结论:可以认为烧结不是受力构件连接工艺,烧结温度太高,产生晶界缝隙并扩展成裂纹,在合适条件下,致使柄折断.     

Novel porous organocatalysts for cycloaddition of CO2 and epoxides

Three classes of organosilicas (DMO, OMOs and PMOs) containing immobilized multi-hydroxyl bis-(quaternary ammonium) iodide salts were prepared and tested in the cycloaddition of CO₂ and epoxides. Owing to its higher surface area, pore volume and optimum nucleophilicity of the iodide ion, OMO-2 with two hydroxyl groups was found to be the most active catalyst. For substrates that are easy to activate such as propylene oxide, 1,2-epoxybutane and epichlorohydrin, excellent yields and selectivities were obtained under mild reaction conditions (0.5 MPa CO₂, 50 °C and 10–15 h). Moreover, OMO-2 showed very good catalytic properties (yield ≥ 93% and selectivity ≥ 98%), and excellent chemical and textural stability in the synthesis of 1,2-butylene carbonate over 5 cycles.

Three classes of organosilicas (DMO, OMOs and PMOs) containing multi-hydroxyl bis-quaternary ammonium iodide were tested in the cycloaddition of CO₂ and epoxides. OMO with two hydroxyl groups was the most active, with good stable and reusability.     

Water splitting by MnFe2O4/Na2CO3 reversible redox reactions

Future energy systems must call upon clean and renewable sources capable of reducing associated CO₂ emissions. The present research opens new perspectives for renewable energy-based hydrogen production by water splitting using metal oxide oxidation/reduction reactants. An earlier multicriteria assessment defined top priorities, with MnFe₂O₄/Na₂CO₃/H₂O and Mn₃O₄/MnO/NaMnO₂/H₂O multistep redox cycles having the highest potential. The latter redox system was previously assessed and proven difficult to be conducted. The former redox system was hence experimentally investigated in the present research at the 0.5 to 250 g scale in isothermal thermogravimetry, an electrically heated furnace, and a concentrated solar reactor. Over 30 successive oxidation/reduction cycles were assessed, and the H₂ production efficiencies exceeded 98 % for the coprecipitated reactant after these multiple cycles. Tentative economics using a coprecipitated reactant revealed that 120 cycles are needed to achieve a 1 € per kg H₂ cost. Improving the cheaper ball-milled reactant could reduce costs by approximately 30 %. The initial results confirm that future research is important.

Investigating H₂ production by MnFe₂O₄/Na₂CO₃/H₂O redox cycles, using different reactants. Using the more efficient coprecipitated reactant, production costs will be ∼1€ per kg H₂, if 120 cycles are achieved. Improving the cheaper ball-milled reactant is recommended.     

连接工艺对多孔层植入体多孔层质量的影响和作用

概况:一般连接工艺是低水平的,使多孔层植入体多孔层产生不少隐患.缺陷:一般连接工艺之所以产生隐患,是它们各自存在的缺陷,不能采用先进的举措予以克服等.应用:活性扩散焊是适用的连接工艺,有许多先进工序.结论:作者提出采用等直径的金属小球,配合以活性扩散焊工艺才能从根本上解决它引起的以应力遮挡为主的隐患.同时活性扩散焊工艺所用到的高性能钎料,其成分对人体无害.     

Formation of cubic perovskite alloy containing the ammonium cation of 2D perovskite for high performance solar cells with improved stability

The perovskite solar cells have demonstrated to be strong competitors for conventional silicon solar cells due to their remarkable power conversion efficiency. However, their structural instability is the biggest obstacle to commercialization. To address these issues, we prepared (CH₃NH₃)_1−x(HC(NH₂)₂)_xPbI₃ (CH₃NH₃ = MA, HC(NH₂)₂ = FA) perovskite alloys that contain ethylammonium (EA, CH₃CH₂NH₃⁺) and benzylammonium (BA, C₆H₅CH₂NH₃⁺) cations with no new additional two-dimensional (2D) perovskite phases. The crystal structures of alloy perovskites exhibit the cubic phase, which decreased the cation disorder and the intrinsic instability compared to 3D MAPbI₃ perovskite. The band gaps of the alloy perovskites are almost the same as the corresponding 3D perovskites, which exhibit a high refractive index, a large absorption coefficient, and paramagnetic properties for the production of high performance photovoltaic devices. After we constructed the solar cell with the configuration of regular (n–i–p) solar cells using the alloy perovskites, the power conversion efficiencies (PCE) of the MA_0.83EA_0.17PbI₃ perovskite solar cell showed the highest efficiency, which was 10.22%, under 1 sun illumination.

We prepared (MA)_1−x(FA)_xPbI₃ (CH₃NH₃ = MA, HC(NH₂)₂ = FA) perovskite alloys that contain ethylammonium (CH₃CH₂NH₃⁺) and benzylammonium (C₆H₅CH₂NH₃⁺) cations with no new additional two-dimensional perovskite phases.     

Coupling selective laser sintering and supercritical CO2 foaming for 3D printed porous polyvinylidene fluoride with improved piezoelectric performance

In this study, a facile strategy coupling selective laser sintering (SLS) and supercritical carbon dioxide (ScCO₂) foaming technology is proposed to prepare a three-dimensional porous polyvinylidene fluoride (PVDF) with an improved piezoelectric output. The effects of foaming conditions including temperature and pressure on foam morphology, crystallization behavior and piezoelectric properties have been systematically studied. It is found that indeed the mechanical stretching foaming process greatly improves the produced content up to 76.2% of the β-phase in PVDF. The piezoelectric output of the PVDF foam with the highest open-circuit voltage could go up to 8 V (4.5 times printed parts), which could light up 4 LED lights and charge 4.7 μF 50 V capacitor to 3.51 V in 275 s. This study provides a feasible approach to 3D porous material fabrication for achieving high-performance piezoelectric materials and demonstrates the promising potential of energy harvesters and smart sensors.

In this study, a facile strategy coupling selective laser sintering (SLS) and supercritical carbon dioxide (ScCO₂) foaming technology is proposed to prepare a three-dimensional porous polyvinylidene fluoride (PVDF) with an improved piezoelectric output.     

Unraveling the mechanism of CO2 capture and separation by porous liquids

Carbon dioxide (CO₂) emissions intensify the greenhouse effect so much that its capture and separation are needed. Porous liquids, possessing both the porous properties of solids and the fluidity of liquids, exhibit a wide range of applications in absorbing CO₂, but the mechanism of gas capture and separation demands in-depth understanding. To this end, we provide a molecular perspective of gas absorption in a porous liquid composed of porous organic cages dissolved in a size-excluded solvent, hexachloropropene, by density functional theory for the first time. In this work, different conformations were considered comprehensively for three representative porous organic cages and molecules. Results show that chloroform, compared to CO₂, tends to enter the cage due to stronger C–H⋯π interaction and the optimal capacity of each cage to absorb CO₂ through hydrogen bonding and π–π interaction is 4, 2 and 4 equivalents, respectively. We hope that these discoveries will promote the synthesis of similar porous liquids that are used to capture and separate gases.

A POC-type porous liquid has the ability to absorb CO₂ and the cage provides a cavity for absorption. The dominant interaction between CO₂ and the cage is π–π interaction. The optimal capacities of the three porous organic cages are 4, 2 and 4 eq.     

Facile morphology control of 3D porous CeO2 for CO oxidation

3D porous CeO₂ with various morphologies was successfully synthesized via a facile precipitation using glycine as the soft bio-template. During the synthesis, it was demonstrated that the morphology of CeO₂ depended on the molar ratio of reactants. Furthermore, the catalytic performance towards CO oxidation of the as-synthesized CeO₂ with different morphologies was investigated. CeO₂ with a bowknot shape showed excellent catalytic performance, giving complete CO conversion at 370 °C, due to its properties of much higher oxygen vacancies, loosely packed pore structure and larger specific surface area.

Different morphologies of CeO₂ were obtained via a green and facial method, which realized CO complete conversion at 370 °C.     

Recovery of FTO coated glass substrate via environment-friendly facile recycling perovskite solar cells

Organic–inorganic perovskite solar cells (PSCs) have recently emerged as a potential candidate for large-scale and low-cost photovoltaic devices. However, the technology is still susceptible to degradation issues and toxicity concerns due to the presence of lead (Pb). Therefore, investigation on ideal methods to deal with PSC wastes once the device attains its end-of-life is crucial and to recycle the components within the cell is the most cost effective and energy effective method by far. This paper reported on a layer-by-layer extraction approach to recycle the fluorine-doped tin oxide (FTO) coated glass substrate which is the most expensive component in the device architecture of mesoporous planar PSC. By adapting the sequential removal of each layer, chemical properties of individual components, including spiro-OMeTAD and gold can be preserved, enabling the material to be easily reused. It also ensured that the toxic Pb component could be isolated without contaminating other materials. The removal of all individual layers allows the retrieval of FTO conductive glass which can be used in various applications that are not only restricted to photovoltaics. Comparison of electrical, morphological and physical properties of recycled FTO glasses to commercial ones revealed minimal variations. This confirmed that the recycling approach was useful in retrieving the substrate without affecting its physicochemical properties.

Organic–inorganic perovskite solar cells (PSCs) have recently emerged as a potential candidate for large-scale and low-cost photovoltaic devices.     

Oxygen and nitrogen enriched pectin-derived micro-meso porous carbon for CO2 uptake

Oxygen and nitrogen enriched micro–meso porous carbon powders have been prepared from pectin and melamine as oxygen and nitrogen containing organic precursors, respectively. The synthesis process has been performed following a solvothermal approach in an alkaline solution during which Pluronic F127 was added to the solution as the soft template. Following the solvothermal treatment, the carbonization process has been performed at 700, 850 and 950 °C. The synthesized porous carbons have been characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), nitrogen adsorption–desorption isotherms and Fourier transform infrared spectroscopy (FTIR). The surface area of 499.5 m² g⁻¹, total pore volume of 0.35 cm³ g⁻¹, and a high nitrogen and oxygen content of 9.3 and 29.1 wt% are displayed for the fine sample. The optimal porous carbon had CO₂ adsorption of up to 3.1 mmol g⁻¹ at 273 K at 1 bar owing to abundant basic nitrogen-containing functionalities and the valuable micro–meso porous structure. Despite the absence of any reagent and also having a relatively moderate specific surface area, compared to similar materials, a very high ratio of adsorption capacity to specific surface area (6.2 μmol m⁻²) was observed. The Elovich kinetic model was found to be the best and the physisorption process was reported.

Oxygen and nitrogen enriched micro–meso porous carbon powders have been prepared from pectin and melamine as oxygen and nitrogen containing organic precursors, respectively.     

Waste wool derived nitrogen-doped hierarchical porous carbon for selective CO2 capture

The goal of this research is to develop a low-cost porous carbon adsorbent for selective CO₂ capture. To obtain advanced adsorbents, it is critical to understand the synergetic effect of textural characteristics and surface functionality of the adsorbents for CO₂ capture performance. Herein, we report a sustainable and scalable bio-inspired fabrication of nitrogen-doped hierarchical porous carbon by employing KOH chemical activation of waste wool. The optimal sample possesses a large surface area and a hierarchical porous structure, and exhibits good CO₂ adsorption capacities of 2.78 mmol g⁻¹ and 3.72 mmol g⁻¹ at 25 °C and 0 °C, respectively, under 1 bar. Additionally, this sample also displays a moderate CO₂/N₂ selectivity, an appropriate CO₂ isosteric heat of adsorption and a stable cyclic ability. These multiple advantages combined with the low-cost of the raw material demonstrate that this sample is an excellent candidate as an adsorbent for CO₂ capture.

In this work, N-doped hierarchical porous carbon has been successfully fabricated by KOH activation of waste wool. The optimal sample exhibits good CO₂ adsorption capacity under atmospheric pressure (1 bar), as well as excellent CO₂/N₂ selectivity.     

Nanostructured copper molybdates as promising bifunctional electrocatalysts for overall water splitting and CO2 reduction

Overall water splitting and CO₂ reduction are two very important reactions from the environmental viewpoint. The former produces hydrogen as a clean fuel and the latter decreases the amount of CO₂ emissions and thus reduces greenhouse effects. Here, we prepare two types of copper molybdate, CuMoO₄ and Cu₃Mo₂O₉, and electrochemically investigate them for water splitting and CO₂ reduction. Our findings show that Cu₃Mo₂O₉ is a better electrocatalyst for full water splitting compared to CuMoO₄. It provides overpotentials, which are smaller than the overpotentials of CuMoO₄ by around 0.14 V at a current density of 1 mA cm⁻² and 0.10 V at −0.4 mA cm⁻², for water oxidation and hydrogen evolution reactions, respectively. However, CuMoO₄ adsorbs CO₂ and the reduced intermediates/products more strongly than Cu₃Mo₂O₉. Such different behaviors of these electrocatalysts can be attributed to their different unit cells.

Comparing overall water splitting on the surface two types of copper molybdate.     

Comparison of water desalination performance of porous graphene and MoS2 nanosheets

Following graphene and its derivatives, molybdenum disulfide (MoS₂) has become a research hotspot in two-dimensional materials. Both graphene and MoS₂ exhibit great potential in water treatment. A variety of nanoporous graphene or MoS₂ membranes have been designed for water desalination. In this work, we compared the water flux and ion rejection of MoS₂ and graphene nanopores, using molecular dynamics simulations. The simulation results demonstrate that monolayer nanopores have higher water fluxes than bilayer nanopores with lower ion rejection rates. MoS₂ nanopores perform better than graphene in terms of water permeability. Exploration of the underlying mechanism indicates that the water molecules in the MoS₂ pores have faster velocity and higher mass density than those in the graphene pores, due to the outer hydrophobic and inner hydrophilic edges of MoS₂ pores. In addition, increasing the polarity of the pore edge causes a decrease in water flux while enhancement of ion rejection. Our findings may provide theoretical guidance for the design of MoS₂ membranes in water purification.

(1) The water flux of MoS₂ is higher than that of graphene with similar pore area regardless of whether monolayer or bilayer. (2) A monolayer has higher water flux than a bilayer. In contrast, a monolayer has lower ion rejection than a bilayer.     

多孔碳酸钙陶瓷与干细胞源性成骨细胞的相容性

背景:国内外的研究证实普通碳酸钙陶瓷作为骨替代材料时具有细胞支架作用。目的:观察多孔碳酸钙陶瓷与成骨细胞的相容性,及作为骨组织工程支架的可能性。方法:SD大鼠骨髓基质干细胞经矿化诱导培养、扩增并检测证实其已具成骨细胞表型后,分别与多孔碳酸钙陶瓷支架、普通羟基磷灰石陶瓷支架体外复合培养。结果与结论:骨髓基质干细胞经体外诱导形成成骨细胞,钙结节、Ⅰ型胶原和碱性磷酸酶免疫染色结果阳性。多孔碳酸钙陶瓷支架材料与羟基磷灰石陶瓷材料皆有细胞附着生长,但多孔碳酸钙陶瓷支架材料细胞的黏附能力、增殖活力及成骨活性均强于羟基磷灰石陶瓷材料。提示多孔碳酸钙陶瓷支架材料与SD大鼠骨髓基质干细胞源性成骨细胞有良好相容性。     

多孔碳酸钙陶瓷与干细胞源性成骨细胞的相容性

背景：国内外的研究证实普通碳酸钙陶瓷作为骨替代材料时具有细胞支架作用。目的：观察多孔碳酸钙陶瓷与成骨细胞的相容性,及作为骨组织工程支架的可能性。方法：SD大鼠骨髓基质干细胞经矿化诱导培养、扩增并检测证实其已具成骨细胞表型后,分别与多孔碳酸钙陶瓷支架、普通羟基磷灰石陶瓷支架体外复合培养。结果与结论：骨髓基质干细胞经体外诱导形成成骨细胞,钙结节、Ⅰ型胶原和碱性磷酸酶免疫染色结果阳性。多孔碳酸钙陶瓷支架材料与羟基磷灰石陶瓷材料皆有细胞附着生长,但多孔碳酸钙陶瓷支架材料细胞的黏附能力、增殖活力及成骨活性均强于羟基磷灰石陶瓷材料。提示多孔碳酸钙陶瓷支架材料与SD大鼠骨髓基质干细胞源性成骨细胞有良好相容性。