A review on recent advances in the electrochemical reduction of CO2 to CO with nano-electrocatalysts

The electrochemical reduction (ECR) of CO₂ is a powerful strategy to reduce the world''s carbon footprint by converting CO₂ to useful products such as CH₃OH and CO. Recent techno-economic analysis has found that for the electro-conversion of CO₂ to be adapted for practical use, the main products formed from this reaction need to be low-order, such as CO. This review summarizes recent progress in the ECR of CO₂ to CO on nano-electrocatalysts (noble, non-noble metals and carbon nanomaterials) and provides the limitations and challenges that each electrocatalyst faces. It discusses the mechanism behind the performance of the electrocatalysts and offers the potential future prospects of the ECR process.

Electrochemical reduction (ECR) of CO₂ reduces world’s carbon footprint by converting CO₂ to useful products such as CH₃OH and CO. This review summarizes recent progress in the ECR of CO₂ to CO on nano-electrocatalysts.     

A study on the electrochemical behavior of hydroquinone at a nanometer cobalt/l-glutamate-modified electrode

A new electrochemical sensor for hydroquinone (HQ) was prepared. The electrochemical sensor was modified by electrodeposition and electrochemical polymerization to modify nanometer cobalt (nano-Co) and poly-l-glutamic acid (poly-l-glu) on the surface of a glassy carbon electrode (GCE). Then, the electrochemical behavior of hydroquinone on the electrochemical sensor was investigated by cyclic voltammetry (CV). The experimental conditions were optimized from the aspects of electrolyte type, concentration, acidity, enrichment time and scanning speed. The experimental results showed that under optimized conditions the oxidation peak current has a good linear relationship with the concentration of hydroquinone in the range of 3.85 × 10⁻⁶ to 1.30 × 10⁻³ mol L⁻¹ (R² = 0.9998). Moreover, there was a low detection limit of 4.97 × 10⁻⁷ mol L⁻¹. When the sensor was used for the analysis of hydroquinone in water samples, the recoveries with satisfactory results were in the range of 97.2–102.6%.

A new electrochemical sensor for hydroquinone (HQ) was prepared.     

Systematic study of TiO2/ZnO mixed metal oxides for CO2 photoreduction

A two component three degree simplex lattice experimental design was employed to evaluate the impact of different mixing fractions of TiO₂ and ZnO on an ordered mesoporous SBA-15 support for CO₂ photoreduction. It was anticipated that the combined advantages of TiO₂ and ZnO: low cost, non-toxicity and combined electronic properties would facilitate CO₂ photoreduction. The fraction of ZnO had a statistically dominant impact on maximum CO₂ adsorption (β₂ = 22.65, p-value = 1.39 × 10⁻⁴). The fraction of TiO₂ used had a statistically significant positive impact on CO (β₁ = 9.71, p-value = 2.93 × 10⁻⁴) and CH₄ (β₁ = 1.43, p-value = 1.35 × 10⁻³) cumulative production. A negative impact, from the interaction term between the fractions of TiO₂ and ZnO, was found for CH₄ cumulative production (β₃ = −2.64, p-value = 2.30 × 10⁻²). The systematic study provided evidence for the possible loss in CO₂ photoreduction activity from sulphate groups introduced during the synthesis of ZnO. The decrease in activity is attributed to the presence of sulphate species in the ZnO prepared, which may possibly act as charge carrier and/or radical intermediate scavengers.

A novel example using a systematic design of experiments mixture design for developing mixed metal oxide photocatalysts for CO₂ photoreduction.     

Improving the photocatalytic reduction of CO2 to CO for TiO2 hollow spheres through hybridization with a cobalt complex

A chemical system with enhanced efficiency for electron generation and transfer was constructed by the integration of TiO₂ hollow spheres with [Co(bipy)₃]²⁺. The introduction of [Co(bipy)₃]²⁺ remarkably enhances the photocatalytic activity of pristine semiconductor photocatalysts for heterogeneous CO₂ conversion, which is attributable to the acceleration of charge separation. Of particular interest is that the excellent photocatalytic activity of the heterogeneous catalysts can be utilised for a universal photocatalytic CO₂ reduction system. Yields of 16.8 μmol CO and 6.6 μmol H₂ can be obtained after 2 h of the photoredox reaction, and the apparent overall quantum yield was estimated to be 0.66% under irradiation at λ = 365 nm. The present findings clearly demonstrate that the integration of electron mediators with semiconductors is a feasible process for the design and development of efficient photochemical systems for CO₂ conversion.

A chemical system with enhanced efficiency for electron generation and transfer was constructed by the integration of TiO₂ hollow spheres with [Co(bipy)₃]²⁺.     

Synergetic effects of Cu/TiO2 sensitized with different cyanine dyes on hydrogen evolution

The production of hydrogen as an alternative fuel is a major challenge for developed countries. To achieve this, photocatalysis is a promising method, which depends mainly on a renewable energy source, namely, the sun. Many derivatives of cyanine-sensitized Cu/TiO₂ were prepared and characterized by XRD, SEM-EDS, TEM, BET surface area and UV-vis spectrophotometry and their photocatalytic activity was studied. The study of hydrogen production over the sensitized photocatalysts confirmed the significant role of the dyes in the enhancement of hydrogen production. Dye molecules harness light radiation to produce strong oxidizing species, such as hydroxyl radicals, which in turn form hydrogen molecules. Combining sonolysis with photocatalysis processes proved that ultrasound waves inhibit the agglomeration of particles and maintain their surface area. This synergetic process increased the efficiency of hydrogen production by 7 times using photocatalysis only.

Cyanine dye derivative-sensitized Cu/TiO₂ was prepared, characterized and investigated in hydrogen production.     

A novel highly selective electrochemical chlorobenzene sensor based on ternary oxide RuO2/ZnO/TiO2 nanocomposites

A novel electrochemical (EC) chlorobenzene (CBZ) sensor was fabricated using a ternary oxide RuO₂/ZnO/TiO₂ nanocomposite (NC)-decorated glassy carbon electrode (GCE). The nanoparticles (NPs) were synthesized by a wet-chemical method and characterized by X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), and ultraviolet-visible (UV-vis) spectroscopy. The synthesized RuO₂/ZnO/TiO₂ NC was layered as thin film on a GCE with Nafion (5% suspension in ethanol) adhesive, and the as-prepared sensor was subjected to CBZ analysis using an electrochemical approach. The calibration of the proposed CBZ sensor was executed with a linear relation of current versus concentration of CBZs known as the calibration curve. The sensitivity (32.02 μA μM⁻¹ cm⁻²) of the CBZ sensor was calculated from the slope of the calibration curve by considering the active surface area of the GCE (0.0316 cm²). The lower detection limit (LD; 98.70 ± 4.90 pM) was also calculated at a signal-to-noise ratio of 3. Besides these, the response current followed a linear relationship with the concentration of chlorobenzene and the linear dynamic range (LDR) was denoted in the range of 0.1 nM to 1.0 μM. Moreover, the CBZ sensor was found to exhibit good reproducibility, reliability, stability, and fast response time. Finally, the sensing mechanism was also discussed with the energy-band theory of ternary doped semiconductor materials. The sensing activity of the proposed sensor was significantly enhanced due to the combined result of depletion layer formation at the heterojunction of RuO₂/ZnO/TiO₂ NCs as well as the activity of RuO₂ NPs as oxidation catalysts. The proposed CBZ sensor probe based on ternary oxide RuO₂/ZnO/TiO₂ NCs was developed with significant analytical parameters for practical application in monitoring the environmental pollutants of CBZs for the safety of environmental fields on a large scale.

A novel electrochemical (EC) chlorobenzene (CBZ) sensor was fabricated using a ternary oxide RuO₂/ZnO/TiO₂ nanocomposite (NC)-decorated glassy carbon electrode (GCE).     

A highly active Ca/Cu/YCeO2–TiO2 catalyst for the transient reduction of NO with CO and naphthalene under oxidizing conditions

The transient combustion of biomass leads to the evolution of a variety of pollutants (NO, CO, organic compounds, and many others) that can react with each other on a suitable catalyst to generate compounds of lower toxicity. Here, the transient reduction of NO with CO and naphthalene in the presence of oxygen was studied on a Ca/Cu/YCeO₂–TiO₂ catalyst. Response surface methodology was used to identify the optimum amounts of calcium, copper, and cerium. The optimized Ca/Cu/YCeO₂–TiO₂ catalyst was then extensively studied and characterized. The coupling of yttrium-stabilized ceria with TiO₂ provided an active support that effectively activated naphthalene. When calcium and copper were added to the support, the obtained Ca/Cu/YCeO₂–TiO₂ catalyst achieved the full conversion of CO and naphthalene and 72% conversion of NO. The Ca/Cu/YCeO₂–TiO₂ catalyst possessed labile oxygen species, which might be related to the high catalytic activity.

A highly-active Ca/Cu/YCeO₂–TiO₂ catalyst shows full conversion of CO and naphthalene and 72% conversion of NO under oxygen.     

Mechanistic study on NO reduction by sludge reburning in a pilot scale cement precalciner with different CO2 concentrations

An experimental study on the effects of CO₂ concentration on the release of reducing gases and the NO reduction efficiency by sludge reburning was carried out in a pilot scale cement precalciner. The results indicate that sludge reburning shows an ideal NO reduction activity. The best NO reduction efficiency of 54% is reached when the CO₂ concentration is 25 vol%. Characteristic analysis of the sludge shows that the main types of reducing gases generated by sludge reburning are HCN, NH₃, CO and CH₄. Among them, CO₂ concentration plays a crucial role in the release of HCN, CO and CH₄. The mechanistic study indicates that NO reduction is dominated by homogeneous reduction during the sludge reburning process, in particular the reducing gases of CO and NH₃ have significant influences on the NO reduction. Meanwhile, the effect of CO₂ concentration on NO reduction is mainly due to the difference in CO release. The results of the present study not only provide insight into the mechanism of NO reduction by sludge reburning, but could also contribute to the development of NO_X removal technology in the cement industry.

The reducing gases of CO and NH₃ produced by sludge reburning make a major contribution to NO reduction.     

两种不同清洁灌肠方法的对比研究

探讨改良清洁灌肠方法对灌肠次数、肠腔清洁效果、病人腹部疼痛、便意感程度的影响.因此,选择需清洁灌肠做直肠、结肠检查的100例病人进行对比研究.     

A comparative study of different electrodeposited NiCo2O4 microspheres anchored on a reduced graphene oxide platform: electrochemical sensor for anti-depressant drug venlafaxine

Two different fabrication methods were performed and compared for preparation of binary metallic oxide microstructures supported on a reduced graphene oxide (rGO) modified graphite electrode. Nickel–Cobalt oxide microspheres (NiCo₂O₄ MSs) were prepared by two different deposition methods: wet chemical and in situ-electrical deposited methods. Different characterization methods were conducted, including cyclic voltammetry (CV), scanning emission microscopy (SEM), electrochemical impedance spectroscopy (EIS) and Raman spectroscopy. The deposition methods of NiCo₂O₄ MSs were found to affect the electrochemical behavior of the modified electrodes towards the oxidation of venlafaxine (VEN), an anti-depressant drug. The fabricated electrode showed linearity over the range 5–500 nmol L⁻¹ and an excellent sensitivity with a limit of detection (LOD) and limit of quantitation (LOQ) of 3.4 and 10.3 nmol L⁻¹, respectively. It was revealed that the wet-NiCo₂O₄@rGO modified electrode prepared by the wet chemical method showed an improved electrochemical behavior for determination of VEN in pharmaceuticals and human plasma with high recovery results in the range of 96.7–98.6% and 96.0–100.7%, respectively without any interference from the co-existing components.

Different electrodeposited NiCo₂O₄ microspheres supported on a reduced graphene oxide platform for electrochemical sensing of venlafaxine.     

临床护理人员洗手后选择干手方法的探讨

目的为临床选择简单、方便、合适的干手方法提供依据。方法将64名临床护士随机分为毛巾干手组（A组）和纸巾f手组（B组）各32名。毛巾下手组于灭菌毛巾挂上时和2h后分别按六步洗手法洗手后采样,再用灭菌毛巾于手后采样;纸巾干手组按六步洗手法洗手后采样,再用一次性纸巾干手后采样。对样本菌落进行检测和判定;同时对两种干手方法进行成本计算。结果洗手后、干手后细菌菌落数合格率比较,A组洗手后84．4％,干手后90．6％;B组洗手后84．4％,干手后93．8％,两组差异均无统计学意义（P〉0．05）;两组方法成本比较,差异无统计学意义（P〉0．05）。结论一次性纸巾和不同时间段的公用灭菌毛巾都能达到干手、洁净的效果,使用一次性纸巾更为简单方便和实用。     

Thermodynamically driven self-formation of Ag nanoparticles in Zn-embedded carbon nanofibers for efficient electrochemical CO2 reduction

The electrochemical CO₂ reduction reaction (CO₂RR), which converts CO₂ into value-added feedstocks and renewable fuels, has been increasingly studied as a next-generation energy and environmental solution. Here, we report that single-atom metal sites distributed around active materials can enhance the CO₂RR performance by controlling the Lewis acidity-based local CO₂ concentration. By utilizing the oxidation Gibbs free energy difference between silver (Ag), zinc (Zn), and carbon (C), we can produce Ag nanoparticle-embedded carbon nanofibers (CNFs) where Zn is atomically dispersed by a one-pot, self-forming thermal calcination process. The CO₂RR performance of AgZn–CNF was investigated by a flow cell with a gas diffusion electrode (GDE). Compared to Ag–CNFs without Zn species (53% at −0.85 V vs. RHE), the faradaic efficiency (FE) of carbon monoxide (CO) was approximately 20% higher in AgZn–CNF (75% at −0.82 V vs. RHE) with 1 M KOH electrolyte.

Ag nanoparticles in Zn-embedded carbon nanofiber were synthesized by a simple one-pot, self-forming strategy. Charged Zn single atoms act as Lewis acidic sites and improving the CO₂ reduction reaction performance of the Ag nanoparticles.     

Compositional and operational impacts on the thermochemical reduction of CO2 to CO by iron oxide/yttria-stabilized zirconia

Ferrites have potential for use as active materials in solar-thermochemical cycles because of their versatile redox chemistry. Such cycles utilize solar-thermal energy for the production of hydrogen from water and carbon monoxide from carbon dioxide. Although ferrites offer the potential for deep levels of reduction (e.g., stoichiometric conversion of magnetite to wüstite) and correspondingly large per-cycle product yields, in practice reactions are limited to surface regions made smaller by rapid sintering and agglomeration. Combining ferrites with zirconia or yttria-stabilized zirconia (YSZ) greatly improves the cyclability of the ferrites and enables a move away from powder to monolithic systems. We have studied the behavior of iron oxides composited with YSZ using thermogravimetric analysis under operando conditions. Samples in which the iron was fully dissolved within the YSZ matrix showed greater overall extent of thermochemical redox and higher rate of reaction than samples with equal iron loading but in which the iron was only partially dissolved, with the rest existing as agglomerates of iron oxide within the ceramic matrix. Varying the yttria content of the YSZ revealed a maximum thermochemical capacity (yield per cycle) for 6 mol% Y₂O₃ in YSZ. The first thermochemical redox cycle performed for each sample resulted in a net mass loss that was proportional to the iron oxide loading in the material and was stoichiometrically consistent with complete reduction of Fe₂O₃ to Fe₃O₄ and further partial reduction of the Fe₃O₄ to FeO. Mass gains upon reaction with CO₂ were consistent with re-oxidation of the FeO fraction back to Fe₃O₄. The Fe dissolved in the YSZ matrix, however, is capable of cycling stoichiometrically between Fe³⁺ and Fe²⁺. Varying the re-oxidation temperature between 1000 and 1200 °C highlighted the trade-off between re-oxidation rate and equilibrium limitations.

The versatile redox chemistry of ferrites makes them useful as active materials for the solar-thermochemical production of synthetic fuels. Optimization of the distribution of iron in a YSZ matrix allows the performance of ferrites to be enhanced.     

Enhanced photocatalytic hydrogen evolution and ammonia sensitivity of double-heterojunction g-C3N4/TiO2/CuO

The performance of semiconductor photocatalysts has been limited by rapid electron–hole recombination. One strategy to overcome this problem is to construct a heterojunction structure to improve the survival rate of electrons. In this context, a novel g-C₃N₄/TiO₂/CuO double-heterojunction photocatalyst was developed and characterized. Its photocatalytic activity for hydrogen production from water–methanol photocatalytic reforming was explored. Methanol is always used to eliminate semiconductor holes. The g-C₃N₄/TiO₂/CuO double-heterojunction photocatalyst with a narrow bandgap of ∼1.38 eV presented excellent photocatalytic activity for hydrogen evolution (97.48 μmol (g h)⁻¹) under visible light irradiation. Compared with g-C₃N₄/TiO₂ and CuO/TiO₂, the photocatalytic activity of g-C₃N₄/TiO₂/CuO for hydrogen production was increased approximately 7.6 times and 1.8 times, respectively. Below 240 °C, the sensitivity of g-C₃N₄/TiO₂/CuO to ammonia was approximately 90% and 46% higher than that of g-C₃N₄/TiO₂ and CuO/TiO₂, respectively. The enhancement of the photocatalytic activity and gas sensing properties of the g-C₃N₄/TiO₂/CuO composite resulted from the close interface contact established by the double heterostructure. The trajectory of electrons in the double heterojunction conformed to the S-scheme. UV-vis, PL, and transient photocurrent characterization showed that the double heterostructure effectively inhibited the recombination of e⁻/h⁺ pairs and enhanced the migration of photogenerated electrons.

The trajectory of electrons in the g-C3N4/TiO2/CuO double-heterojunction conforms to the S-scheme.     

不同吸痰方法对PEEP患者血流动力学影响的研究

目的 研究开放式吸痰与密闭式吸痰对人工机械通气使用PEEP患者心率(HR)、无创血压(NBP)、中心静脉压(CVP)、心输出量(CO)、心脏指数(CI)、每搏射血量(SV)、左心室作功(LCW)、左心室每搏作功(LVSW)、预射血间期(PEP)等的影响.方法 收集2010年1～10月应用机械通气使用PEEP患者,随机分...     

Attitudes of physiotherapists and physiotherapy students toward euthanasia: A comparative study

This interventional study was undertaken to assess the impact of physiotherapy education on the knowledge and attitudes of physiotherapists (PTs) and physiotherapy students (PSs) toward euthanasia. The study, which was conducted during the period between 2004 and 2005, included a total of 494 participants (311 PTs; 183 PSs) aged 18 to 52 y from the western and central portions of Turkey, who responded to a self-report questionnaire (response rate, 96.4%) that was based on data from the literature. Results indicated that PTs (48.9%) were more likely to approve of euthanasia than PSs (38.3%) (P<.05). The legalization of euthanasia was favored by 43.7% of PTs, compared with 29.5% of PSs (P<.05). On the other hand, PTs and PSs expressed similar views regarding euthanasia, including reasons for accepting or opposing euthanasia and acceptable conditions for its use (P> .05). Overall results showed that sex and age had no effect on whether euthanasia was accepted (P> .05); religiousness was found to have the greatest effect on attitudes toward euthanasia (P<.05). The findings of the current study suggest that (1) the attitudes of PTs are different from those of PSs, and (2) the Islamic point of view has a negative impact on the attitudes of PTs and PSs toward euthanasia.     

Correction: Mechanistic study on NO reduction by sludge reburning in a pilot scale cement precalciner with different CO2 concentrations

Correction for ‘Mechanistic study on NO reduction by sludge reburning in a pilot scale cement precalciner with different CO₂ concentrations’ by Xiang Xiao et al., RSC Adv., 2019, 9, 22863–22874.

Affiliation a was incorrect in the published article; the correct version is shown here.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.