Understanding Bridging Sites and Accelerating Quantum Efficiency for Photocatalytic CO_(2) Reduction

We report a novel double-shelled nanoboxes photocatalyst architecture with tailored interfaces that accelerate quantum efficiency for photocatalytic CO_(2) reduction reaction(CO_(2)RR)via Mo–S bridging bonds sites in S_(v)–In_(2)S_(3)@2H–MoTe_(2).The X-ray absorption near-edge structure shows that the formation of S_(v)–In_(2)S_(3)@2H–MoTe_(2) adjusts the coordination environment via interface engineering and forms Mo–S polarized sites at the interface.The interfacial dynamics and catalytic behavior are clearly revealed by ultrafast femtosecond transient absorption,time-resolved,and in situ diffuse reflectance–Infrared Fourier transform spectroscopy.A tunable electronic structure through steric interaction of Mo–S bridging bonds induces a 1.7-fold enhancement in S_(v)–In_(2)S_(3)@2H–MoTe_(2)(5)photogenerated carrier concentration relative to pristine S_(v)–In_(2)S_(3).Benefiting from lower carrier transport activation energy,an internal quantum efficiency of 94.01%at 380 nm was used for photocatalytic CO_(2)RR.This study proposes a new strategy to design photocatalyst through bridging sites to adjust the selectivity of photocatalytic CO_(2)RR.

Cu-Based Materials for Enhanced C_(2+) Product Selectivity in Photo-/Electro-Catalytic CO_(2) Reduction: Challenges and Prospects

Carbon dioxide conversion into valuable products using photocatalysis and electrocatalysis is an effective approach to mitigate global environmental issues and the energy shortages. Among the materials utilized for catalytic reduction of CO_(2), Cu-based materials are highly advantageous owing to their widespread availability, cost-effectiveness, and environmental sustainability. Furthermore, Cu-based materials demonstrate interesting abilities in the adsorption and activation of carbon dioxide, allowing the formation of C_(2+) compounds through C–C coupling process. Herein, the basic principles of photocatalytic CO_(2) reduction reactions(PCO_(2)RR) and electrocatalytic CO_(2) reduction reaction(ECO_(2)RR) and the pathways for the generation C_(2+) products are introduced. This review categorizes Cu-based materials into different groups including Cu metal, Cu oxides, Cu alloys, and Cu SACs, Cu heterojunctions based on their catalytic applications. The relationship between the Cu surfaces and their efficiency in both PCO_(2)RR and ECO_(2)RR is emphasized. Through a review of recent studies on PCO_(2)RR and ECO_(2)RR using Cu-based catalysts, the focus is on understanding the underlying reasons for the enhanced selectivity toward C_(2+) products. Finally, the opportunities and challenges associated with Cu-based materials in the CO_(2) catalytic reduction applications are presented, along with research directions that can guide for the design of highly active and selective Cu-based materials for CO_(2) reduction processes in the future.

Preferentially selective extraction of lithium from spent LiCoO_(2)cathodes by medium-temperature carbon reduction roasting

Lithium recovery from spent lithium-ion batteries(LIBs)have attracted extensive attention due to the skyrocketing price of lithium.The medium-temperature carbon reduction roasting was proposed to preferential selective extraction of lithium from spent Li-CoO_(2)(LCO)cathodes to overcome the incomplete recovery and loss of lithium during the recycling process.The LCO layered structure was destroyed and lithium was completely converted into water-soluble Li2CO_(3)under a suitable temperature to control the reduced state of the cobalt oxide.The Co metal agglomerates generated during medium-temperature carbon reduction roasting were broken by wet grinding and ultrasonic crushing to release the entrained lithium.The results showed that 99.10%of the whole lithium could be recovered as Li2CO_(3)with a purity of 99.55%.This work provided a new perspective on the preferentially selective extraction of lithium from spent lithium batteries.

Engineering of oxygen vacancy and bismuth cluster assisted ultrathin Bi_(12)O_(17)Cl_(2)nanosheets with efficient and selective photoreduction of CO_(2)to CO

The photocatalytic conversion of CO_(2)into solar‐powered fuels is viewed as a forward‐looking strategy to address energy scarcity and global warming.This work demonstrated the selective photoreduction of CO_(2)to CO using ultrathin Bi_(12)O_(17)Cl_(2)nanosheets decorated with hydrothermally synthesized bismuth clusters and oxygen vacancies(OVs).The characterizations revealed that the coexistences of OVs and Bi clusters generated in situ contributed to the high efficiency of CO_(2)–CO conversion(64.3μmol g^(−1)h^(−1))and perfect selectivity.The OVs on the facet(001)of the ultrathin Bi_(12)O_(17)Cl_(2)nanosheets serve as sites for CO_(2)adsorption and activation sites,capturing photoexcited electrons and prolonging light absorption due to defect states.In addition,the Bi‐cluster generated in situ offers the ability to trap holes and the surface plasmonic resonance effect.This study offers great potential for the construction of semiconductor hybrids as multiphotocatalysts,capable of being used for the elimination and conversion of CO_(2)in terms of energy and environment.

The photo-decomposition and self-restructuring dynamic equilibrium mechanism of Cu_(2)(OH)_(2)CO_(3)for stable photocatalytic CO_(2)reduction

Developing suitable photocatalysts and understanding their intrinsic catalytic mechanism remain key challenges in the pursuit of highly active,good selective,and long-term stable photocatalytic CO_(2)reduction(PCO_(2)R)systems.Herein,monoclinic Cu_(2)(OH)_(2)CO_(3)is firstly proven to be a new class of photocatalyst,which has excellent catalytic stability and selectivity for PCO_(2)R in the absence of any sacrificial agent and cocatalysts.Based on a Cu_(2)(OH)_(2)^(13)CO_(3)photocatalyst and 13CO_(2)two-sided^(13)C isotopic tracer strategy,and combined with in situ diffused reflectance infrared Fourier transform spectroscopy(DRIFTS)analysis and density functional theory(DFT)calculations,two main CO_(2)transformation routes,and the photo-decomposition and self-restructuring dynamic equilibrium mechanism of Cu_(2)(OH)_(2)CO_(3)are definitely revealed.The PCO_(2)R activity of Cu_(2)(OH)_(2)CO_(3)is comparable to some of state-of-the-art novel photocatalysts.Significantly,the PCO_(2)R properties can be further greatly enhanced by simply combining Cu_(2)(OH)_(2)CO_(3)with typical TiO_(2)to construct composites photocatalyst.The highest CO_(2)and CH_(4)production rates by 7.5 wt%Cu_(2)(OH)_(2)CO_(3)-TiO_(2)reach 16.4μmol g^(-1)h^(-1)and 116.0μmol g^(-1)h^(-1),respectively,which are even higher than that of some of PCO_(2)R systems containing sacrificial agents or precious metals modified photocatalysts.This work provides a better understanding for the PCO_(2)R mechanism at the atomic levels,and also indicates that basic carbonate photocatalysts have broad application potential in the future.

Exploring the impact of Nafion modifier on electrocatalytic CO_(2) reduction over Cu catalyst

Nafion as a universal polymer ionomer was widely applied for nanocatalysts electrode preparation.However,the effect of Nafion on electrocatalytic performance was often overlooked,especially for CO_(2)electrolysis.Herein,the key roles of Nafion for CO_(2)RR were systematically studied on Cu nanoparticles(NPs)electrocatalyst.We found that Nafion modifier not only inhibit hydrogen evolution reaction(HER)by decreasing the accessibility of H_(2)O from electrolyte to Cu NPs,and increase the CO_(2)concentration at electrocatalyst interface for enhancing the CO_(2)mass transfer process,but also activate CO_(2)molecule by Lewis acid-base interaction between Nafion and CO_(2)to accelerate the formation of^(*)CO,which favor of C–C coupling for boosting C_(2)product generation.Owing to these features,the HER selectivity was suppressed from 40.6%to 16.8%on optimal Cu@Nafion electrode at-1.2 V versus reversible hydrogen electrode(RHE),and as high as 73.5%faradaic efficiencies(FEs)of C_(2)products were achieved at the same applied potential,which was 2.6 times higher than that on bare Cu electrode(~28.3%).In addition,Nafion also contributed to the long-term stability by hinder Cu NPs morphology reconstruction.Thus,this work provides insights into the impact of Nafion on electrocatalytic CO_(2)RR performance.

Porous metal oxides in the role of electrochemical CO_(2) reduction reaction

The global energy-related CO_(2) emissions have rapidly increased as the world economy heavily relied on fossil fuels.This paper explores the pressing challenge of CO_(2) emissions and highlights the role of porous metal oxide materials in the electrocatalytic reduction of CO_(2)(CO_(2)RR).The focus is on the development of robust and selective catalysts,particularly metal and metal-oxide-based materials.Porous metal oxides offer high surface area,enhancing the accessibility to active sites and improving reaction kinetics.The tunability of these materials allows for tailored catalytic behavior,targeting optimized reaction mechanisms for CO_(2)RR.The work also discusses the various synthesis strategies and identifies key structural and compositional features,addressing challenges like high overpotential,poor selectivity,and low stability.Based on these insights,we suggest avenues for future research on porous metal oxide materials for electrochemical CO_(2) reduction.

Surface engineering of ZnO electrocatalyst by N doping towards electrochemical CO_(2) reduction

The discovery of efficient,selective,and stable electrocatalysts can be a key point to produce the largescale chemical fuels via electrochemical CO_(2) reduction(ECR).In this study,an earth-abundant and nontoxic ZnO-based electrocatalyst was developed for use in gas-diffusion electrodes(GDE),and the effect of nitrogen(N)doping on the ECR activity of ZnO electrocatalysts was investigated.Initially,a ZnO nanosheet was prepared via the hydrothermal method,and nitridation was performed at different times to control the N-doping content.With an increase in the N-doping content,the morphological properties of the nanosheet changed significantly,namely,the 2D nanosheets transformed into irregularly shaped nanoparticles.Furthermore,the ECR performance of Zn O electrocatalysts with different N-doping content was assessed in 1.0 M KHCO_(3) electrolyte using a gas-diffusion electrode-based ECR cell.While the ECR activity increased after a small amount of N doping,it decreased for higher N doping content.Among them,the N:ZnO-1 h electrocatalysts showed the best CO selectivity,with a faradaic efficiency(FE_(CO))of 92.7%at-0.73 V vs.reversible hydrogen electrode(RHE),which was greater than that of an undoped Zn O electrocatalyst(FE_(CO)of 63.4%at-0.78 V_(RHE)).Also,the N:ZnO-1 h electrocatalyst exhibited outstanding durability for 16 h,with a partial current density of-92.1 mA cm^(-2).This improvement of N:ZnO-1 h electrocatalyst can be explained by density functional theory calculations,demonstrating that this improvement of N:ZnO-1 h electrocatalyst comes from(ⅰ)the optimized active sites lowering the free energy barrier for the rate-determining step(RDS),and(ⅱ)the modification of electronic structure enhancing the electron transfer rate by N doping.

Bimetallic In_(2)O_(3)/Bi_(2)O_(3) Catalysts Enable Highly Selective CO_(2) Electroreduction to Formate within Ultra-Broad Potential Windows

CO_(2)electrochemical reduction reaction(CO_(2)RR)to formate is a hopeful pathway for reducing CO_(2)and producing high-value chemicals,which needs highly selective catalysts with ultra-broad potential windows to meet the industrial demands.Herein,the nanorod-like bimetallic ln_(2)O_(3)/Bi_(2)O_(3)catalysts were successfully synthesized by pyrolysis of bimetallic InBi-MOF precursors.The abundant oxygen vacancies generated from the lattice mismatch of Bi_(2)O_(3)and ln_(2)O_(3)reduced the activation energy of CO_(2)to*CO_(2)·^(-)and improved the selectivity of*CO_(2)·^(-)to formate simultaneously.Meanwhile,the carbon skeleton derived from the pyrolysis of organic framework of InBi-MOF provided a conductive network to accelerate the electrons transmission.The catalyst exhibited an ultra-broad applied potential window of 1200 mV(from-0.4 to-1.6 V vs RHE),relativistic high Faradaic efficiency of formate(99.92%)and satisfactory stability after 30 h.The in situ FT-IR experiment and DFT calculation verified that the abundant oxygen vacancies on the surface of catalysts can easily absorb CO_(2)molecules,and oxygen vacancy path is dominant pathway.This work provides a convenient method to construct high-performance bimetallic catalysts for the industrial application of CO_(2)RR.

Ultrafine ordered L1_(2)-Pt-Co-Mn ternary intermetallic nanoparticles as high-performance oxygen-reduction electrocatalysts for practical fuel cells

The long-range periodically ordered atomic structures in intermetallic nanoparticles(INPs)can significantly enhance both the electrocatalytic activity and electrochemical stability toward the oxygen reduction reaction(ORR)compared to the disordered atomic structures in ordinary solid-solution alloy NPs.Accordingly,through a facile and scalable synthetic method,a series of carbon-supported ultrafine Pt_3Co_(x)Mn_(1-x)ternary INPs are prepared in this work,which possess the"skin-like"ultrathin Pt shells,the ordered L1_(2) atomic structure,and the high-even dispersion on supports(L1_(2)-Pt_3Co_(x)Mn_(1-x)/~SPt INPs/C).Electrochemical results present that the composition-optimized L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C exhibits the highest electrocata lytic activity among the series,which are also much better than those of the pristine ultrafine Pt/C.Besides,it also has a greatly enhanced electrochemical stability.In addition,the effects of annealing temperature and time are further investigated.More importantly,such superior ORR electrocatalytic performance of L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C are also well demonstrated in practical fuel cells.Physicochemical characterization analyses further reveal the major origins of the greatly enhanced ORR electrocata lytic performance:the Pt-Co-Mn alloy-induced geometric and ligand effects as well as the extremely high L1_(2) atomic-ordering degree.This work not only successfully develops a highly active and stable ordered ternary intermetallic ORR electrocatalyst,but also elucidates the corresponding"structure-function"relationship,which can be further applied in designing other intermetallic(electro)catalysts.

Highly selective photocatalytic reduction of CO_(2) to CH_(4) on electron-rich Fe species cocatalyst under visible light irradiation

Efficient photocatalytic reduction of CO_(2) to high-calorific-value CH4,an ideal target product,is a blueprint for C_(1)industry relevance and carbon neutrality,but it also faces great challenges.Herein,we demonstrate unprecedented hybrid SiC photocatalysts modified by Fe-based cocatalyst,which are prepared via a facile impregnation-reduction method,featuring an optimized local electronic structure.It exhibits a superior photocatalytic carbon-based products yield of 30.0μmol g^(−1) h^(−1) and achieves a record CH_(4) selectivity of up to 94.3%,which highlights the effectiveness of electron-rich Fe cocatalyst for boosting photocatalytic performance and selectivity.Specifically,the synergistic effects of directional migration of photogenerated electrons and strongπ-back bonding on low-valence Fe effectively strengthen the adsorption and activation of reactants and intermediates in the CO_(2)→CH_(4) pathway.This study inspires an effective strategy for enhancing the multielectron reduction capacity of semiconductor photocatalysts with low-cost Fe instead of noble metals as cocatalysts.

Preparation of low-oxygen titanium powder by magnesiothermic reduction of TiO2 assisted by MgCl_(2)−HoCl_(3) molten salt

To reduce the production cost of titanium,a new method for direct preparation of low-oxygen titanium powder by the magnesiothermic reduction of TiO_(2) with the assistance of a MgCl_(2)−HoCl_(3) molten salt was proposed.Thermodynamic calculations showed that the magnesiothermic reduction of TiO_(2) was feasible.However,hindrance of the reduction reaction by the reduction by-product of MgO resulted in a considerably high O concentration in the titanium powder.The addition of HoCl_(3) to the system significantly reduces the activity of MgO to produce low-oxygen titanium powder.Thermochemical deoxidation and reduction experiments were conducted with MgCl_(2)−HoCl_(3) molten salt in the temperature range of 1023−1273 K.The results showed that titanium powder with oxygen concentration(mass fraction)below 5.00×10^(-4) can be prepared at the Mg−MgCl_(2)−HoOCl−HoCl_(3) equilibrium.

Insights into Reduction of CO_(2)to CO Catalyzed by Pyramidal-4Ni Clusters Supported on Doped CeO_(2)

Converting CO_(2)into valuable chemicals has become a widely used research method for CO_(2)conversion.In this work,the catalytic performance of pyramidal-4Ni catalysts supported on rare earth metal-doped CeO_(2)towardCO_(2)reductionreaction(CO_(2)RR)was investigated by using density-functional theorycalculations.For rare earth metal-doped CeO_(2),2Ce is substituted by 2 trivalent cations and at the same time one oxygen vacancy is created to make charge compensation.We investigated the oxygen vacancy nearest(Vo,N)and next-nearest(Vo,NN)to 4Ni,and found releasing CO and CO_(2)dissociation are the rate-determining steps,respectively,via the path of Vo,N and Vo,NN.Among the studied dopants(Ga,Sb,Lu,Gd,Pr,La,Bi),Gd is identified as the best dopant for catalyzing the reduction of CO_(2)at 823 K,with the turn-over frequency(TOF)of 104 times as large as that over 4Ni supported on pure CeO_(2).This exploration provides theoretical support and guidance for the research and application of rare earth metaldoped CeO_(2)-loaded Ni catalysts in the field of CO_(2)reduction.

Pre-reduction of WO_(3)-Co_(3)O_(4)by H_(2)-C_(2)H_4 in a fluidized bed

In order to avoid the formation ofηphase(W_(6)Co_(6)C or W_(3)Co_(3)C)that adversely affects the sintering process and its products in the preparation process of ultra-fine WC-Co powder,a technical route of prereduction of WO_(3)-Co_(3)O_(4)to WO_(2)-Co and then deep reduction carbonization to WC-Co powder has been proposed.This study mainly investigates the influence of gas partial pressure on the pre-reduction process of WO_(3)-Co_(3)O_(4)under a mixed atmosphere of H_(2)-C_(2)H_(4)-Ar at 600℃and establishes the kinetic equations of pre-reduction and carbon evolution.The results indicate that increasing the partial pressure of hydrogen is conducive to the rapid and complete conversion of WO_(3) to WO_(2).High carbon content can be generated by the deposition of C_(2)H_(4),and it hinders the diffusion of the reducing gas;WO_(3)still cannot be completely reduced to WO_(2)as the partial pressure of C_(2)H_(4) increases to 60%.For the carbon evolution of C_(2)H_(4),the carbon amount is positively related to the H_(2)partial pressure,but it shows the highest amount and evolution rate when the ethylene partial pressure is 20%.Based on the reduction rate curves of WO_(3) and carbon evolution rate curves of C_(2)H_(4),the rate equations of pre-reduction and carbon evolution of WO_(3)-Co_(3)O_(4)system at 600℃are established.The pre-reduction reaction belongs to the first-order reaction,and its equation is expressed as follows:r=-(dw_(WO_(3)))/dt=(9±0.15)×10^(-2)×P_(H_(2))^(0.44)P_(C_(2)H_(4))&(0.57)The carbon deposition rate equation of C_(2)H_(4) can be expressed as follows:r=-(dc_C)/dt=r_f-r_b≌7.35×10^(-2)×P_(C_(2)H_(4))^(0.31)

A dendritic Cu/Cu_(2)O structure with high curvature enables rapid and efficient reduction of carbon dioxide to C_(2) in an H-cell

Electrocatalytic reduction of CO_(2)(CO_(2)RR)to multicarbon products is an efficient approach for ad-dressing the energy crisis and achieving carbon neutrality.In H-cells,achieving high-current C_(2)products is challenging because of the inefficient mass transfer of the catalyst and the presence of the hydrogen evolution reaction(HER).In this study,dendritic Cu/Cu_(2)O with abundant Cu^(0)/Cu^(+)interfaces and numerous dendritic curves was synthesized in a CO_(2)atmosphere,resulting in the high selectivity and current density of the C_(2)products.Dendritic Cu/Cu_(2)O achieved a C_(2)Faradaic efficiency of 69.8%and a C_(2)partial current density of 129.5 mA cm^(-2)in an H-cell.Finite element simulations showed that a dendritic structure with a high curvature generates a strong electric field,leading to a localized CO_(2)concentration.Additionally,DRT analysis showed that a dendritic struc-ture with a high curvature actively adsorbed the surrounding high concentration of CO_(2),enhancing the mass transfer rate and achieving a high current density.During the experiment,the impact of the electronic structure on the performance of the catalyst was investigated by varying the atomic ratio of Cu^(0)/Cu^(+) on the catalyst surface,which resulted in improved ethylene selectivity.Under the optimal atomic ratio of Cu^(0)/Cu^(+),the charge transfer resistance was minimized,and the desorption rate of the intermediates was low,favoring C_(2) generation.Density functional theory calculations indicated that the Cu^(0)/Cu^(+) interfaces exhibited a lower Gibbs free energy for the rate-determining step,enhancing C_(2)H_(4) formation.The Cu/Cu_(2)O catalyst also exhibited a low Cu d-band center,which enhanced the adsorption stability of *CO on the surface and facilitated C_(2)formation.This observa-tion explained the higher yield of C_(2) products at the Cu^(0)/Cu^(+) interface than that of H_(2) under rapid mass transfer.The results of the net present value model showed that the H-cell holds promising industrial prospects,contingent upon it being a catalyst with both high selectivity and high current density.This approach of integrating the structure and composition provides new insights for ad-vancing the CO_(2)RR towards high-current C_(2) products.

Unraveling the roles of atomically-dispersed Au in boosting photocatalytic CO_(2)reduction and aryl alcohol oxidation

Atomically-dispersed metal-based materials represent an emerging class of photocatalysts attributed to their high catalytic activity,abundant surface active sites,and efficient charge separation.Nevertheless,the roles of different forms of atomically-dispersed metals(i.e.,single-atoms and atomic clusters)in photocatalytic reactions remain ambiguous.Herein,we developed an ethylenediamine(EDA)-assisted reduction method to controllably synthesize atomically dispersed Au in the forms of Au single atoms(Au_(SA)),Au clusters(Au_(C)),and a mixed-phase of Au_(SA)and Au_(C)(Au_(SA+C))on CdS.In addition,we elucidate the synergistic effect of Au_(SA)and Au_(C)in enhancing the photocatalytic performance of CdS substrates for simultaneous CO_(2)reduction and aryl alcohol oxidation.Specifically,Au_(SA)can effectively lower the energy barrier for the CO_(2)→*COOH conversion,while Au_(C)can enhance the adsorption of alcohols and reduce the energy barrier for dehydrogenation.As a result,the Au_(SA)and Au_(C)co-loaded CdS show impressive overall photocatalytic CO_(2)conversion performance,achieving remarkable CO and BAD production rates of 4.43 and 4.71 mmol g^(−1)h^(−1),with the selectivities of 93%and 99%,respectively.More importantly,the solar-to-chemical conversion efficiency of Au_(SA+C)/CdS reaches 0.57%,which is over fivefold higher than the typical solar-to-biomass conversion efficiency found in nature(ca.0.1%).This study comprehensively describes the roles of different forms of atomically-dispersed metals and their synergistic effects in photocatalytic reactions,which is anticipated to pave a new avenue in energy and environmental applications.

Single-atom modified graphene cocatalyst for enhanced photocatalytic CO_(2) reduction on halide perovskite

Metal halide perovskite(MHP)has become one of the most promising materials for photocatalytic CO_(2) reduction owing to the wide light absorption range,negative conduction band position and high reduction ability.However,photoreduction of CO_(2) by MHP remains a challenge because of the slow charge separation and transfer.Herein,a cobalt single-atom modified nitrogen-doped graphene(Co-NG)cocatalyst is prepared for enhanced photocatalytic CO_(2) reduction of bismuth-based MHP Cs_(3)Bi_(2)Br_(9).The optimal Cs_(3)Bi_(2)Br_(9)/Co-NG composite exhibits the CO production rate of 123.16μmol g^(-1)h^(-1),which is 17.3 times higher than that of Cs_(3)Bi_(2)Br_(9).Moreover,the Cs_(3)Bi_(2)Br_(9)/Co-NG composite photocatalyst exhibits nearly 100% CO selectivity as well as impressive long-term stability.Charge carrier dynamic characterizations such as Kelvin probe force microscopy(KPFM),single-particle PL microscope and transient absorption(TA)spectroscopy demonstrate the vital role of Co-NG cocatalyst in accelerating the transfer and separation of photogenerated charges and improving photocatalytic performance.The reaction mechanism has been demonstrated by in situ diffuse reflectance infrared Fourier-transform spectroscopy measurement.In addition,in situ X-ray photoelectron spectroscopy test and theoretical calculation reveal the reaction reactive sites and reaction energy barriers,demonstrating that the introduction of Co-NG promotes the formation of ^(*)COOH intermediate,providing sufficient evidence for the highly selective generation of CO.This work provides an effective single-atom-based cocatalyst modification strategy for photocatalytic CO_(2) reduction and is expected to shed light on other photocatalytic applications.

Poly(ethylenimine)-assisted synthesis of hollow carbon spheres comprising multi-sized Ni species for CO_(2) electroreduction

Electrochemical CO_(2) reduction to produce value-added chemicals and fuels is one of the research hotspots in the field of energy conversion.The development of efficient catalysts with high conductivity and readily accessible active sites for CO_(2) electroreduction remains challenging yet indispensable.In this work,a reliable poly(ethyleneimine)(PEI)-assisted strategy is developed to prepare a hollow carbon nanocomposite comprising a single-site Ni-modified carbon shell and confined Ni nanoparticles(NPs)(denoted as Ni@NHCS),where PEI not only functions as a mediator to induce the highly dispersed growth of Ni NPs within hollow carbon spheres,but also as a nitrogen precursor to construct highly active atomically-dispersed Ni-Nx sites.Benefiting from the unique structural properties of Ni@NHCS,the aggregation and exposure of Ni NPs can be effectively prevented,while the accessibility of abundant catalytically active Ni-Nx sites can be ensured.As a result,Ni@NHCS exhibits a high CO partial current density of 26.9 mA cm^(-2) and a Faradaic efficiency of 93.0% at-1.0 V vs.RHE,outperforming those of its PEI-free analog.Apart from the excellent activity and selectivity,the shell confinement effect of the hollow carbon sphere endows this catalyst with long-term stability.The findings here are anticipated to help understand the structure-activity relationship in Ni-based carbon catalyst systems for electrocatalytic CO_(2) reduction.Furthermore,the PEI-assisted synthetic concept is potentially applicable to the preparation of high-performance metal-based nanoconfined materials tailored for diverse energy conversion applications and beyond.

Modified Cu active sites by alloying for efficient electrocatalytic reduction CO_(2) to CO

Transition metals like Au,Ag,and Cu have been reported to be quite active for CO_(2) reduction.In this study,we use density functional theory(DFT)calculation to investigate the electronic structure and catalytic performance of Au,Ag,Cu and their alloys for CO_(2) reduction reaction(CO_(2)RR).Theoretical calculations identified the combination of Ag,Cu,and Au in a face-centered cubic(fcc)alloy as an outstanding electrocatalyst for CO_(2) reduction to CO,with Cu as the active site.The d-orbital projected density of state(PDOS)profile suggests that alloying alters the electronic structure of the Cu site,thereby affecting the Gibbs free energy change for the formation of*COOH intermediate(ΔG_(*COOH)).To demonstrate the theoretical prediction experimentally,we employ a top-down dealloying approach to synthesize a nanoporous structured AgCuAu alloy(NP-Ag_(5)Cu_(5)Au_(5)).Electrochemical experiments validate that the ternary alloy catalyst is clearly better than unary and binary catalysts,showing a Faradaic efficiency(FE)for CO over 90%across a broad potential range of 0.6 V,with a peak of approximately 96%at-0.573 V vs.RHE.This study underscores the potential of multi-component alloys in CO_(2)RR and establishes a theoretical basis for designing efficient catalysts for CO_(2) utilization.

Electrocatalytic CO_(2)reduction to syngas

While carbon dioxide(CO_(2))is a major greenhouse gas,it is also an important C1 resource.In the trend of energy conservation and emission reduction,electrocatalytic reduction has become a very promising strategy for CO_(2)utilization because it can convert CO_(2)directly to high-valued chemicals and fuels under mild conditions.In particular,the product CO and by-product H_(2)can be combined into syngas by an electrocatalytic CO_(2)reduction reaction(CO_(2)RR)in an aqueous medium.Different molar ratios of CO and H_(2)may be used to produce essential bulk chemicals or liquid fuels such as methanol,alkanes,and olefins through thermochemical catalysis,Fischer-Tropsch synthesis,microbial fermentation,and other techniques.This work discusses the latest strategies in controlling the molar ratio of CO/H_(2)and improving the yield of CO_(2)RR-to-syngas.The challenges of electrocatalytic syngas production are analyzed from an industrial application perspective,and the possible measures to overcome them are proposed in terms of new catalyst design,electrolyte innovation,flow reactor optimization,anodic reaction coupling,and operando technique application.