CO2 Reduction Performance Research Articles

Nickel single-atom synergistic iron-nitrogen sites for efficient CO2 electroreduction at a wide potential range

Recently, diatomic site catalysts (DASCs) by introducing a second metal active site have become a research focus in electrochemical CO2 reduction reaction (eCO2RR), as can regulate electronic structure of metal centers and optimize reaction free energies. However, hitherto the studies on the origin of the outstanding performance of DASCs and the accurate identification of active centers are not still clear. Herein, we designed a nickel–iron diatomic site catalyst by loading highly dispersed iron phthalocyanine (FePc) on a nickel single-atom with ultrathin porous nitrogen-doped carbon nanosheet substrate (denoted as FePc/M-LNi-NC). Experimental and calculational results prove that the synergistic catalysis of FePc and carbon nanosheet based Ni single-atom endowed FePc/M-LNi-NC achieving excellent CO2 reduction performance with a maximum CO Faradaic efficiency of 98.8 % at –0.8 V vs. RHE. In particular, the current density of FePc/M-LNi-NC at −1.0 V vs. RHE in an H-type cell (−20.9 mA/cm2) is 5.6 times that of FePc (3.7 mA/cm2). Compared with M-LNi-NC, the potential range of FePc/M-LNi-NC when FECO above 95 % expands from 0.31 to 0.43 V. Density functional theory calculations reveal that the Fe site in FePc/M-LNi-NC has a lower free energy change for *COOH formation (ΔG*COOH) and CO desorption (ΔGCO) than Ni site, thus exhibits higher electrocatalytic activity. Furthermore, the ΔG*COOH on FePc/M-LNi-NC declines from 0.78 to 0.08 eV compared to M-LNi-NC, and the ΔGCO lowers from 1.36 to 0.33 eV compared to FePc, thus FePc/M-LNi-NC achieves high performance for eCO2RR at a wide potential range.

Fabrication of double modified electrocatalyst by dual flame synthesis for enhancing electrochemical reduction of carbon dioxide

A rapid dual flame synthesis is developed for one-step preparation and modification of double modified ZnO catalysts with carbon doping and oxygen vacancies. The growth mechanism and nanostructure evolution are also investigated. The double modified ZnO with carbon doping and oxygen vacancies exhibies excellent performance in CO2 reduction to syngas, with a high current density of 14.02 mA/cm2 at −1.1 V vs. RHE and a maximum Faradaic efficiency of 71% for CO production. The maximum adjustable range of the CO/H2 ratio from 0.5 to 2.7. In a flow cell, the double modified ZnO exhibits a large current density of 126.8 mA/cm2 at −1.2 V vs. RHE. The maximum Faradaic efficiency for CO2 reduction to CO is 74.8% at 50 mA/cm2. Double modified ZnO maintains stable potential and Faradaic efficiency for over 5 h of electrolysis. Operando X-ray absorption spectroscopy and density functional theory calculations reveal that the active site is the Zn–Zn configuration, and that carbon dopant and oxygen vacancy promote CO2 activation and CO desorption, and reduce reaction overpotential of CO2RR.

Shaping and Doping Metal-Organic Framework-Derived TiO2 to Steer the Selectivity of Photocatalytic CO2 Reduction toward CH4.

Steering selectivity in photocatalytic conversion of CO2, especially toward deep reduction products, is vital to energy and environmental goals yet remains a great challenge. In this work, we demonstrate a facet-dependent photocatalytic selective reduction of CO2 to CH4 in Cu-doped TiO2 catalysts exposed with different facets synthesized by a topological transformation from MIL-125 (Ti) precursors. The optimized round cake-like Cu/TiO2 photocatalyst mainly exposed with the (001) facet exhibited a high photocatalytic CO2 reduction performance with a CH4 yield of 40.36 μmol g-1 h-1 with a selectivity of 94.1%, which are significantly higher than those of TiO2 (001) (4.70 μmol g-1 h-1 and 52.6%, respectively), Cu/TiO2 (001 + 101) (18.95 μmol g-1 h-1 and 69.6%, respectively), and Cu/TiO2 (101) (14.73 μmol g-1 h-1 and 78.9%, respectively). The results of experimental and theoretical calculations demonstrate that the Cu doping dominating the promoted separation and migration efficiencies of photogenerated charges and the preferential adsorption on (001) facets synergistically contribute to the selective reduction of CO2 to CH4. This work highlights the significance of synergy between facet engineering and ion doping in the design of high-performance photocatalysts with respect to selective reduction of CO2 to multielectron products.

Theoretical study on the electrochemical CO2 reduction performance of MoS2-supported Ni single atoms with transition metal substrate doping

In the context of increasing energy issues and climate change, the development of electrochemical CO2 reduction strategies using single atom catalysts (SACs) presents a viable solution by converting CO2 into high-value-added products. Transition metal dichalcogenides (TMDs) have emerged as the main candidates for SACs in electrocatalytic CO2 reduction reaction (CO2RR) catalysts. The regulation of the second coordination sphere of SACs is known to modulate their electronic structure and catalytic behavior. This study delves into the effect of transition metal-doped substrates on SACs. We employed spin-polarization density functional theory (DFT) to design a series of Ni/TM-MoS2 monolayer MoS2 materials, with transition metals (including Cr, Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, W, Re, Os, Ir, Pt and Au) substituting the Mo atoms and anchoring single atom Ni. Among them, six Ni/TM-MoS2 catalysts doped with Mn, Fe, Co, Ru, Rh, and Ir demonstrate enhanced CO2RR activity and selectivity when compared to unmodified Ni/MoS2. The Ni/Ru-MoS2 SAC exhibits the best catalytic activity and selectivity for formic acid production, with a limiting potential (UL) of -0.06 V. The incorporation of the metal-doped substrate lowers the work function of the catalyst, facilitating electron transfer and reaction progression. Furthermore, a volcanic relationship was observed between the work function and UL. This study provides strategic insights into the design and development of SACs, highlighting the potential for future modifications and applications.

PAN-assisted preparation of Bi2MoO6 with enhanced photocatalytic CO2 reduction performance

In this study, to improve photocatalytic CO2 reduction efficiency of Bi2MoO6-based photocatalysts, Bi2MoO6 (BMO) was synthesized via a solvothermal method with the assistance of polyacrylonitrile (PAN). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were utilized to evaluate the microstructures, phases, and elemental compositions of the samples. Additionally, the separation and migration efficiency of photogenerated charge pairs during the photocatalytic process were analyzed in detail using surface photovoltage spectroscopy (SPS), photoluminescence spectrum (PL), transient photocurrent density (TPR), and electrochemical impedance spectroscopy (EIS). In comparison with the reference sample, the specific surface area of 2 % BMO (mass ratios of PAN/Bi(NO3)3·5H2O is 2 %) has been increased to 39.6 m2/g, which increases by 0.9 times compared to the reference sample. The successful introduction of oxygen vacancies (OVs) in Bi2MoO6 was confirmed by low-temperature electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS), and suitable OVs is favorable for separation and migration of the photogenerated carriers. The experimental results indicate that the separation efficiency of photogenerated carriers in the PAN-BMO photocatalyst is significantly boosted in contrast to the reference sample. Furthermore, all photocatalysts exhibit higher photocatalytic CO2 reduction activity than the reference sample. It is noteworthy that the 2 % BMO sample shows the highest photocatalytic CO2 reduction activity, and the average photocatalytic CO2 reduction yield over the 2 % BMO reaches 2.16 μmol g−1 h−1, which is 2.25 times higher than that on the reference sample (0.96 μmol g−1 h−1). In view of the findings, photocatalytic CO2 reduction mechanism for BMO with OVs was rationally proposed.

Boosted photocatalytic performance of CO2 reduction and RhB oxidation over CaCO3/g-C3N4 composite with highly effective holes transfer

Boosted photocatalytic performance of CO2 reduction and RhB oxidation over CaCO3/g-C3N4 composite with highly effective holes transfer

Bimetallic NiCu catalyst derived from spent MOF adsorbent for efficient photocatalytic CO2 reduction

The metal–organic frameworks (MOFs) rich in porous structures and their derivatives have been widely developed and applied to heavy metal adsorption. However, little attention has been paid to the subsequent treatment and reutilization of spent MOFs adsorbents. A potential feasible strategy is to develop MOFs-derived bimetallic catalysts for energy conversion. Herein, a bimetallic Ni-Cu2O-Cu/C nanocomposite (Ni-Cu/C) derived from spent Cu-based MOFs (CuBTC) adsorbents was fabricated and applied to improve the performance of photocatalytic CO2 reduction. The results demonstrate that Ni doping could improve the charge transfer dynamics. The synthesized Ni-Cu/C catalyst exhibits a high CO yield (12.45 μmol g−1 h−1) in the pure water system in the absence of other photosensitizers and sacrificial agents, which is 2.05 folds higher compared to Cu/C. The CO2 conversion selectivity of the synthesized Ni-Cu/C catalyst reaches up to 99.0%. The mechanism of photocatalytic CO2 reduction reaction was further investigated by in-situ experiments and density functional theory calculation. The in-situ FT-IR characterization show that photogenerated electrons could effectively adsorb CO2 to produce CO2− and optimize *CO immediate. This work not only emphasizes the unique design of bimetallic catalyst derived from spent MOFs adsorbent, but also contributes a feasible solution to its reutilization for enhanced CO2 conversion.

A novel S-scheme photocatalyst Fe2O3/Bi2O3/g-C3N4 with enhanced visible-light photocatalytic performance for antibiotic degradation and CO2 reduction: RSM-based optimization

The degradation of pollutants and reduction of CO2 to hydrocarbon fuels using photocatalysis is a potential approach to reducing CO2 emissions and decreasing environmental contamination. This study introduces an innovative S-scheme photocatalyst (Fe2O3/Bi2O3/g-C3N4) synthesized through simple methods for the first time. The structural, morphological, and optical properties of the synthesized photocatalysts were comprehensively characterized using XRD, XPS, FTIR, SEM, TEM, HR-TEM, BET, UV–vis DRS, PL, ESR, and mott-Schottky analyses, respectively. The visible light photodegradation of tetracycline (TC) antibiotic and CO2 conversion were carried out in order to evaluate the photocatalytic performance of these synthesized materials. Using the RSM-CCD approach, the influence of key variables on TC degradation were optimized. The results indicated that the optimized photocatalyst (45-FeBiC) exhibited higher photocatalytic performance (99.87 %) compared to other samples via photogenerated •O2−, and •OH. Additionally, four cycle studies verified that the 45-FeBiC nanocomposite had adequate photostability. After 6 h of visible light illumination, the 45-FeBiC catalyst generated 33.84 μmol/g of CO and maintained 96.2 % of its initial photocatalytic activity after 30 h of reaction. The enhanced photocatalytic efficiency of the 45-FeBiC nanocomposite is attributed to the photosensitization effect of 3 wt%-Fe2O3/Bi2O3 on g-C3N4 within the S-scheme photocatalytic framework.

Molecular Solvation Environment Controls the Active Site in Cation-Mediated Electrocatalytic CO2 Reduction to Methanol

Electrocatalytic synthesis of higher-value products from waste molecules is an emerging technique for sustainable chemical catalysis. Heterogeneous molecular electrocatalysts are an important group of materials where the catalytic activity and selectivity can be controlled using molecularly defined active sites. Despite extensive efforts to synthesize better molecular catalysts, the effects of molecular aggregation, which dominates the interaction of the catalyst with the electrode surface as well as with the electrochemical solvation environment, are not fully understood. Using cobalt phthalocyanine (CoPc) dispersed on carbon nanotubes (CNTs) as a model system, we find that controlling the direct interaction of the molecular catalyst with cations in the electrochemical double layer (EDL) results in significantly enhanced performance for CO2 reduction (CO2RR). Specifically, molecular dispersion of the CoPc onto CNTs yields a 4-fold increase in total current density and 8-fold increase in methanol (MeOH) selectivity compared to aggregated CoPc physically mixed with the same CNT support, enabling CO2 to MeOH conversion with 42.34% Faradaic efficiency (FE). Using surface-selective sum-frequency generation (SFG) vibrational spectroscopy, direct detection of reaction intermediates reveals that the potential-dependent adsorption of two distinct CO intermediates at two types of active sites, one less active and producing mostly CO, the other more active and able to produce methanol. DFT calculations show that the CO intermediate responsible for selective MeOH production results from the direct interaction with cations present in the EDL. This interaction, which is only possible when CoPc is molecularly dispersed on the electrode surface, is responsible for the cation-assisted conversion of CO to MeOH. Control experiments using either strongly hydrated Li+, or chelated K+ by 18-crown-6-ether, which suppress MeOH formation, further confirms the important role of this interaction. Similarly significant enhancement effects are also observed for nitrate reduction reaction (NO3RR) and oxygen reduction reaction (ORR), showing that dispersing molecular catalysts into monomers states is a general design parameter required to enhance activity and selectivity by cation-assisted reaction kinetics inside the EDL.

Aggregation of Homogeneous Porphyrin Catalysts in Organic Electrolyte Broadly Inhibits Electrochemical CO2 Reduction Performance

Metalloporphyrins are widely used as homogeneous electrocatalysts for the production of renewable fuels from abundant feedstocks and sustainable energy. The modularity of porphyrin catalysts has led to the establishment of structure‐function correlations that aid in predicting and optimizing catalytic activity. Although metalloporphyrins are widely known to aggregate due to their planar structure that promotes π–π stacking, it is surprising that the influence of metalloporphyrin aggregation on electrocatalytic performance has not been previously investigated. Herein, we will document the relative aggregation and electrocatalytic activity for CO2 reduction to CO with three structurally related iron meso-phenylporphyrins in commonly used N,N-dimethylformamide (DMF) electrolyte. An inverse dependence of kinetics on catalyst concentration is observed for all three porphyrins based on cyclic voltammetry data. Furthermore, this inhibition extends to bulk electrolysis performance, where up to 75% of the catalyst in a 1 mM solution is inactive compared to in a 0.25 mM solution. This talk will additionally discuss how aggregation is influenced by organic additives, axial ligands, redox state, metal identity, and porphyrin substituents. Overall, this work emphasizes that metalloporphyrins can aggregate severely (even in well-solubilizing organic electrolytes) and that aggregation effects must be considered for optimization of performance and for meaningful catalytic activity comparisons.

Membrane Electrode Assembly Development for Industrial CO2 Electrolysis

Membrane electrode assemblies (MEAs) are the key components of zero-gap CO2 electrolyzers, having various functions in the electrolysis process. The catalyst layers serve as the reaction interface, the porous transport layers ensure reactant and product transport to and from the catalysts, while the membrane is responsible for the ion transport between the two half cells. Thus, the structure of the MEA has a determining role on the electrolyzer operation. Industrial application requires large surface area electrolyzers and / or assembly of stacks. The scale-up, however, imposes different challenges on MEA preparation and on electrolyzer operation, therefore the optimal operating conditions can not necessarily be translated from small-scale (< 10 cm2) experiments.With the aim to scale-up the CO2 electrolysis to an industrially relevant level (>2500 cm2 active area), we thoroughly study the MEA components in a test electrolyzer cell having 100 cm2 active area. Currently we focus mainly on the optimization of the catalyst layers and the porous transport layers. The used electrolyzer size is already large enough that we can draw relevant conclusions for the operation of the large-scale electrolyzer, however, still offers possibility to screen a wide range of parameters.I will present selected results on how the improvement of the quality of the catalyst layers - through the optimization of the catalyst ink and the coating process- results in enhanced CO2 reduction performance. We also focus on the screening of different porous transport layers on the anode side with the long-term goal to reduce the precious metal consumption of the CO2 electrolysis. In the second part of my presentation, I will show how the operational parameters (e.g. cell temperature, humidity) affect the stability of the electrolysis. We have thoroughly investigated one of the biggest issues of the anion exchange membrane CO2 electrolysis: the carbonate precipitate formation and the related flooding phenomenon. We identified the pressure drop at the cathode side as a key test output parameter, which can serve as an early warning for the start of the undesired precipitation. When it is recognized in time, and the adequate preventive measures are applied, the lifetime of the electrolyzers can be greatly improved.

Tree-inspired semiconductor-on-ceramic 2D/1D heterostructure for efficient CO2 photoreduction

Two-dimension nanosheets are ideal photocatalysts for CO2 reduction due to their high exposure of active sites and short charge transfer pathway. However, 2D photocatalysts have a tendency to agglomeration, thus compromising the performance of photocatalytic CO2 reduction. Trees, one of the most important plants for photosynthesis, have a unique “leaf-on-branch” structure. This unique two-dimension/one-dimension (2D/1D) configuration maximizes the adsorption of CO2 molecules and light harvesting. Herein, a tree-inspired semiconductor-on-ceramic 2D/1D heterostructure for efficient photocatalytic CO2 reduction is reported. The cobalt silicate (CoSi) nanosheets (∼0.68 nm) are in situ grown on the surfaces of hydroxyapatite (HAP) nanowires, creating a well-defined 2D/1D hierarchical structure. The vertical alignment of ultrathin CoSi nanosheets on the HAP nanowires effectively suppresses their agglomeration, leading to a large BET surface area (106.45 m2/g) and excellent CO2 adsorption (8.00 cm3 g−1). The results of photoelectrochemical characterization demonstrate that the 2D/1D hierarchical structure is powerful to expedite charge transfer. As a result, the gas generation rate of CO is as high as 28780 μmol g−1 h−1 over the CoSi-on-HAP 2D/1D heterostructure. In addition, the electron transfer mechanism and reaction pathways of CO2 reduction are revealed by in situ irradiated XPS and in situ DRIFT spectra.

Nanoengineering construction of g-C3N4/Bi2WO6 S-scheme heterojunctions for cooperative enhanced photocatalytic CO2 reduction and pollutant degradation

S-scheme heterojunction photocatalysts featuring efficient charge transport paths provide a promising strategy for cooperative achieving photocatalytic CO2 reduction reaction (CO2RR) and Rhodamine B (RhB) degradation. In this work, S-scheme heterojunctions composed of g-C3N4 nanosheets coated on Bi2WO6 nanosheets were prepared by a one-step hydrothermal method, resulting in broad-spectrum light absorption, high electron–hole separation efficiency, and excellent photocatalytic CO2 reduction and RhB oxidization performance. Mechanistic analysis revealed the formation of a directional charge transport path at the interface of the heterojunction, which maintained a high oxidation and reduction potential and improved the efficiency of photoexcited carrier separation. In particular, the synergistic reaction system showed excellent photoredox activity compared with the two separate half-reactions. The optimal catalyst 15CN/BWO displayed the highest CO2 conversion efficiency, with CO and CH4 generation rates of 4.3 and 2.7 μmol g−1h−1, respectively, and the degradation efficiency of the composite heterojunction was significantly higher than that of its constituent materials. This work provides a new possibility for designing a novel dual-function photocatalytic reaction system.

The performance of CO2 reduction by dielectric barrier discharge plasma coupled Cu-Ni binary silicon-based composites

As a major greenhouse gas, the rational conversion and utilization of CO2 can help reduce carbon emissions and mitigate the greenhouse effect. In this study, mesoporous SiO2 as a carrier, with CuO and NiO employed to construct a binary metal composite silica-based catalyst, coupled with dielectric barrier discharge (DBD) plasma, for the conversion of CO2. Physicochemical analysis confirmed the successful introduction of CuO into the mesoporous SiO2. NiO and CuO bimetals were dispersed on SiO2 surfaces with large specific surface areas, ensuring an optimal distribution of metal oxide. Gas chromatography was utilized to investigate the performance of DBD-coupled x%CuO-3 %NiO/Si for CO2 conversion. The results indicated that the CuO-NiO binary composite silica catalysts significantly improved CO2 conversion, CO yield, and energy efficiency compared to the monometallic 3 %NiO/Si materials. Further microstructural analysis of the 9 %CuO-3 %NiO/Si catalyst revealed near-elliptic particles with dimensions of 200 by 500 nm and a large number of irregular fine particles attached to the surface. When the CuO loading reached an optimal level and the input power was set at 30 W, the energy efficiency of the 9 %CuO-3 %NiO/Si catalyst increased by 119.6 %. The CuO-NiO binary composite Si-based catalyst developed in this study boasts simple operation and environmental friendliness, making it highly significant for CO2 treatment.

Synergetic regulation of interfacial electronic structure of Cu, N co-doped carbon modified TiO2 for efficient photocatalytic CO2 reduction

TiO2 was a promising candidate material for CO2 photoreduction, but its development was greatly limited due to inherent defects such as high recombination rate of photogenerated charge carriers and limited number of active sites. In this study, a method involving chelation of metal ions with amino acids followed by high-temperature pyrolysis was employed to prepare Cu, N co-doped carbon-modified TiO2 composite materials, aiming to enhance the photocatalytic CO2 reduction performance of TiO2. The introduction of Cu, N co-doped carbon effectively improved the surface morphology of TiO2, increased the specific surface area and porosity, and enhanced the adsorption capacity of CO2. Simultaneously, the modification of TiO2 by Cu, N co-doped carbon optimized the electronic structure of catalysts, facilitating the separation and transfer of photogenerated electron-hole pairs, reducing charge carrier recombination, and thereby synergistically improving the thermodynamics and kinetics of CO2 reduction. Photocatalytic performance tests revealed that 10 % Cu-TiO2 exhibited the best CO2 reduction performance at a calcination temperature of 450 °C, with a CO production rate of up to 46 μmol·g−1·h−1, approximately 18 times that of pure TiO2. Density functional theory (DFT) calculations further confirmed that the introduction of Cu, N co-doped carbon reduced the Gibbs free energy of the CO2 reduction reaction, promoting the reaction. This study provides a simple, cost-effective strategy for developing efficient photocatalytic CO2 reduction materials.

Identification of intrinsic vacancies and polarization effect on ternary halo‐sulfur‐bismuth compounds for efficient CO2 photoreduction under near‐infrared light irradiation

AbstractTernary halo‐sulfur bismuth compound Bi19X3S27 (X = Cl, Br, I) with distinct electronic structure and full‐spectrum light‐harvesting properties show great application potential in the CO2 photoreduction field. However, the relationship between photocatalytic CO2 reduction performance and the function of halogens in Bi19X3S27 is still poorly understood. Herein, a series of Bi19X3S27 nanorod photocatalysts with intrinsic X and S dual vacancies were developed, which showed significant near‐infrared (NIR) light responses. The types and concentrations of intrinsic vacancies were confirmed and quantified by positron annihilation spectrometry and electron spin resonance spectroscopy. Experimental results showed that Br atoms and intrinsic vacancies (dual Br‐S) in Bi19Br3S27 could greatly enhance the internal polarized electric field and improve the transfer and separation of photogenerated carriers compared with Bi19Cl3S27 and Bi19I3S27. Theoretical calculations revealed that Br atoms in Bi19Br3S27 could facilitate CO2 adsorption and activation and decrease the formation energy of reactive hydrogen. Among Bi19X3S27 nanorods, Bi19Br3S27 nanorods revealed the highest CO2 photoreduction activity with CO yield rate of 28.68 and 2.28 μmol gcatalyst−1 h−1 with full‐spectrum and NIR lights, respectively. This work presents an atomic understanding of the intrinsic vacancies and halogen‐mediated CO2 photoreduction mechanism.

MOFs-derived S-scheme ZnO/BiOBr heterojunction with rich oxygen vacancy for boosting photocatalytic CO2 reduction

In this paper, a MOFs-derived S-scheme ZnO/BiOBr heterojunction photocatalyst was constructed by a one-step calcination method. It was found that the dodecahedral ZnO was well attached to the BiOBr hollow rods in ZnO/BiOBr composites, which could simultaneously introduce oxygen vacancies and enhance interfacial interactions. The photocatalytic CO2 reduction results exhibited that ZnO/BiOBr, without adding any sacrificial agent and photosensitiser, produced CO and CH4 at rates of 21.13 μmol·g−1·h−1 and 2.2 μmol·g−1·h−1 under simulated sunlight, with a CO selectivity of 74.34 %, which was 6.35 and 4.07 times higher than that of the original BiOBr as well as the original ZnO 4.14 and 1.98 times, respectively. The optimised ZnO/BiOBr has excellent photocatalytic CO2 reduction performance. The ZnO/BiOBr photocatalyst has excellent stability after 5 cycles. The unique heterostructures and matched energy band potentials between ZnO and BiOBr provided close interfacial contacts, a large number of active sites and effective charge transferred for photocatalytic CO2 reduction. Furthermore, the mechanism of photocatalytic CO2 reduction for S-scheme ZnO/BiOBr heterojunction was also proposed. Therefore, the MOFs-derived ZnO/BiOBr composites had the potential to be used as photocatalyst for CO2 reduction, providing a rational design idea for solar energy-driven CO2 conversion of MOFs-structured photocatalysts.

Design of a Rotating Disk Electrode setup operating under high pressure and temperature: Application to CO2 reduction on gold

We describe the design and development of a rotating disk electrode (RDE) cell capable of operating at pressures up to 200 bar and temperatures up to 200 °C. This setup enables electrochemical surface characterization through techniques such as voltammetry and impedance spectroscopy, under different mass transport regimes. Furthermore, evaluation of catalytic performance, including CO2 reduction, is possible as the system works in a semi-continuous mode interfaced with online gas sample measurements. As a proof of concept of the high-pressure cell designed, we examined the temperature-dependent changes in the cyclic voltammograms (CVs) of polycrystalline gold up to 150 °C and 50 bar. Additionally, online catalytic performance of CO2 reduction to CO on a rotating polycrystalline gold disk electrode was investigated under different pressure and temperature. Our results indicate a positive impact of temperature on the faradaic efficiency (FE) towards CO up to 50 °C, beyond which a rapid drop in performance was observed at atmospheric pressure. Conversely, increasing pressure positively affected CO2 solubility in the electrolyte, resulting in enhanced FE towards CO, reaching approximately 90 % at 6 bar compared to 40 % at atmospheric pressure. Notably, further increases in pressure did not significantly alter the FE, but led to higher current densities. Moreover, at pressures exceeding 6 bar, we observed a plateau in efficiency at temperatures higher than 50 °C. This observation suggests that increasing pressure can sustain CO2 electrolysis, validating the hypothesis that increasing CO2 solubility would suppress catalytic decay at higher temperatures. This study opens up promising avenues for future investigations in electrocatalysis, ranging from fundamental explorations of surface modifications induced by variations in temperature and pressure to the development of high-performance catalysts.

Novel spherical InVO4/floral Bi2MoO6 Z-scheme heterojunction for efficient photocatalytic carbon dioxide reduction

The development of efficient CO2 reduction photocatalysts is of great significance to improving the global greenhouse effect and alleviating the energy crisis. In this paper, spherical InVO4/floral Bi2MoO6 (IVO/BMO) Z-scheme heterojunction was prepared by a hydrothermal method, and the surface structure, chemical composition, and photovoltaic properties of the samples were characterized and tested for their CO2 reduction performance. The experimental results show that 1.5 %-IVO/BMO exhibits excellent photocatalytic activity for CO2 reduction under the irradiation of 300 W Xenon lamp, with a CO yield of 34.08 µmol/g/h and a CH4 yield of 4.49 µmol/g/h, which are 2.55 and 1.05 times higher than that of the pure Bi2MoO6, respectively. The enhanced photocatalytic activity can be attributed to the formation of an IVO/BMO Z-scheme heterojunction, which promotes electron separation and reduces charge recombination at the interface, facilitating the reaction process. This study provides a novel Z-scheme photocatalyst for efficient carbon dioxide reduction.

High-throughput screening of single-atom catalysts on 1 T-TMD for highly active and selective CO2 reduction reaction: Computational and machine learning insights

The study of transition metals and various possible surface compositions has sparked great interest in low-cost materials, which exhibit high activity and selectivity in catalysis. While various single-atom catalysts loaded on transition metal dichalcogenide (TMD) substrates with excellent CO2 reduction performance have been identified, the relationship between catalytic activity and the intrinsic properties of TMD single-atom catalysts remains unclear. Hence, a high-throughput first-principle computational approach is proposed to screen 24 transition metals anchored on 8 TMD monolayers to determine their catalytic activity in CO2RR. The results show that Fe@CoS2, Pt@TiTe2 and Co@CoS2 exhibit exceptional performances with low CO2RR limiting-potentials of −0.045 eV, 0.75 eV, and 0.54 eV, respectively, showcasing selective pathways towards formic acid (HCOOH), methane (CH4), and methanol (CH3OH). Employing the Sure Independence Screening and Sparsifying Operator method(SISSO), key descriptors linking the performance of single-atom catalysts with their intrinsic features are identified, providing insights for the discovery of superior CO2RR catalysts. Moreover, it was observed that a feature of the anchored single atom, the difference between covalent radius and atomic radius (CR-R), is associated with multiple crucial reaction steps, exhibiting a strong linear relationship with the charge transfer of *COOH. This work not only identifies promising CO2RR catalysts but also establishes a predictive framework for screening catalysts based on their intrinsic properties, paving the way for future advancements in CO2 reduction research.