Dual-Atom-Site Sn-Cu/C3N4 Photocatalyst Selectively Produces Formaldehyde from CO2 Reduction

The solar-driven catalytic reduction of CO₂ to value-added chemicals is under intensive investigation. The reaction pathway via *OCHO intermediate (involving CO₂ adsorbed through O-binding) usually leads to the two-electron transfer product of HCOOH. Herein, a single-atom catalyst with dual-atom-sites featuring neighboring Sn(II) and Cu(I) centers embedded in C₃N₄ framework is developed and characterized, which markedly promotes the production of HCHO via four-electron transfer through the *OCHO pathway. The optimized catalyst achieves a high HCHO productivity of 259.1 µmol g⁻¹ and a selectivity of 61% after 24 h irradiation, which is ascribed to the synergic role of the neighboring Sn(II)–Cu(I) dual-atom sites that stabilize the target intermediates for HCHO production. Moreover, adsorbed *HCHO intermediate is detected by in situ Fourier transform infrared spectroscopy (CO stretches at 1637 cm⁻¹). This study provides a unique example that controls the selectivity of the multi-electron transfer mechanisms of CO₂ photoconversion using heteronuclear dual-atom-site catalyst to generate an uncommon product (HCHO) of CO₂ reduction.     

Proton Turnover Dominated Cascade Route for CO2 Photoreduction

Photoreduction carbon dioxide (CO₂) and water (H₂O) into valuable chemicals is a huge potential to mitigate immoderate CO₂ emissions and energy crisis. To date, tremendous attention is concentrated on the improvement of independent CO₂ reduction or H₂O oxidation behaviors. However, the simultaneous control of efficient electron and hole utilization is still a huge challenge due to the complex cascade redox reactions. Here, a proton turnover exists in the whole CO₂ photoreduction process is discovered, which is defined as the pivot to concatenate the hole and electron behaviors. As a demonstration of the concept, the efficient activated hydrogen (*H) production centers of copper (Cu) and rapid hydrogenation centers of nickel (Ni) are coupled by an alloying strategy, and the proton turnover behaviors could be directly determined by adjustment of the molar ratios of Cu_xNi_y. Moreover, Cu₃Ni₁–TiO₂ exhibits the highest electron selectivity of 93.7% for methane (CH₄) production with a rate of 175.9 µmol g⁻¹ h⁻¹, while Cu₁Ni₅–TiO₂ reaches up to the highest carbon monoxide (CO) electron selectivity and generation rate at 84.4% and 164.6 µmol g⁻¹ h⁻¹, respectively. Consequently, the experimental and theoretical analysis all clarify the predominate proton turnover effect during the overall CO₂ photoreduction process, which directly determines the categories and generated efficiency of C-based products by regulating variable reaction pathways. Therefore, the revelation of the proton turnover pivot could broaden the new sights by bidirectional optimization of dynamics during the overall CO₂ photoreduction system, which favors the efficient, selective, and stable photocatalytic CO₂ reduction with H₂O.     

Interlayer Spacing Regulation by Single-Atom Indiumδ+–N4 on Carbon Nitride for Boosting CO2/CO Photo-Conversion

Simultaneous optimization on bulk photogenerated-carrier separation and surface atomic arrangement of catalyst is crucial for reactivity of CO₂ photo-reduction. Rare studies capture the detail that, better than in-plane regulation, interlayer-spacing regulation may significantly influence the carrier transport of the bulk-catalyst thereby affecting its CO₂ photo-reduction in g-C₃N₄. Herein, through a single atom-assisted thermal-polymerization process, single-atom In-bonded N-atom (In^δ+–N₄) in the (002) crystal planes of g-C₃N₄ is originally constructed. This In^δ+–N₄ reduces the (002) interplanar spacing of g-C₃N₄ by electrostatic adsorption, which significantly enhances the separation of bulk carriers and greatly promotes the reactivity of CO₂ photoreduction. The CO₂ photo-conversion performance of this resulted single-atom In modified g-C₃N₄ is significantly superior to other single atom loaded carbon nitride catalysts. Moreover, the In^δ+–N₄ enhances the CO₂ adsorption on g-C₃N₄, reduces the *COOH formation energy, and optimizes the reaction path. It achieves a remarkable 398.87 µmol g⁻¹ h⁻¹ yield rate, 0.21% apparent quantum efficiency, and nearly 100% selectivity for CO without any cocatalyst or sacrificial agent. Through d₍₀₀₂₎ modulation of carbon nitride by single In atom, this study provides a ground-breaking insight for reactivity enhancement from a double-gain view of bulk structural control and surface atomic arrangement for CO₂-reduction photocatalysts.     

A New Strategy for Accelerating Dynamic Proton Transfer of Electrochemical CO2 Reduction at High Current Densities

Developing single-atom electrocatalysts with high activity and superior selectivity at a wide potential window for CO₂ reduction reaction (CO₂RR) still remains a great challenge. Herein, a porous Ni N C catalyst containing atomically dispersed Ni N₄ sites and nanostructured zirconium oxide (ZrO₂@Ni-NC) synthesized via a post-synthetic coordination coupling carbonization strategy is reported. The as-prepared ZrO₂@Ni-NC exhibits an initial potential of −0.3 V, maximum CO Faradaic efficiency (F.E.) of 98.6% ± 1.3, and a low Tafel slope of 71.7 mV dec⁻¹ in electrochemical CO₂RR. In particular, a wide potential window from −0.7 to −1.4 V with CO F.E. of above 90% on ZrO₂@Ni-NC far exceeds those of recently developed state-of-the-art CO₂RR electrocatalysts based on Ni N moieties anchored carbon. In a flow cell, ZrO₂@Ni-NC delivers a current density of 200 mA cm⁻² with a superior CO selectivity of 96.8% at −1.58 V in a practical scale. A series of designed experiments and structural analyses identify that the isolated Ni N₄ species act as real active sites to drive the CO₂RR reaction and that the nanostructured ZrO₂ largely accelerates the protonation process of *CO₂⁻ to *COOH intermediate, thus significantly reducing the energy barrier of this rate-determining step and boosting whole catalytic performance.     

Molecular Modulation of Sequestered Copper Sites for Efficient Electroreduction of Carbon Dioxide to Methane

The sustainable production of methane (CH₄) via the electrochemical conversion of carbon dioxide (CO₂) is an appealing approach to simultaneously mitigating carbon emissions and achieving energy storage in chemical bonds. Copper (Cu) is a unique material to produce hydrocarbons and oxygenates. However, selective methane generation on Cu remains a great challenge due to the preferential *CO dimerization pathway toward multi-carbon (C₂₊) products at neighboring catalytic sites. Herein, a conjugated copper phthalocyanine polymer (CuPPc) is designed by a facile solid-state method for highly selective CO₂-to-CH₄ conversion. The spatially isolated Cu N₄ sites in CuPPc favor the *CO protonation to generate the key *CHO intermediate, thus significantly promoting the formation of CH₄. As a result, the CuPPc catalyst exhibits a high CH₄ Faradaic efficiency of 55% and a partial current density of 18 mA cm⁻² at −1.25 V versus the reversible hydrogen electrode. It also stably operates for 12 h. This study may offer a new solution to regulating the chemical environment of the active sites for the development of highly efficient copper-based catalysts for electrochemical CO₂ reduction.     

Atomically Defined Undercoordinated Active Sites for Highly Efficient CO2 Electroreduction

Electrocatalytic reduction of carbon dioxide (CO₂ER) in rechargeable Zn–CO₂ battery still remains a great challenge. Herein, a highly efficient CO₂ER electrocatalyst composed of coordinatively unsaturated single‐atom copper coordinated with nitrogen sites anchored into graphene matrix (Cu–N₂/GN) is reported. Benefitting from the unsaturated coordination environment and atomic dispersion, the ultrathin Cu–N₂/GN nanosheets exhibit a high CO₂ER activity and selectivity for CO production with an onset potential of ?0.33 V and the maximum Faradaic efficiency of 81% at a low potential of ?0.50 V, superior to the previously reported atomically dispersed Cu–N anchored on carbon materials. Experimental results manifest the highly exposed and atomically dispersed Cu–N₂ active sites in graphene framework where the Cu species are coordinated by two N atoms. Theoretical calculations demonstrate that the optimized reaction free energy for Cu–N₂ sites to capture CO₂ promote the adsorption of CO₂ molecules on Cu–N₂ sites; meanwhile, the short bond lengths of Cu–N₂ sites accelerate the electron transfer from Cu–N₂ sites to *CO₂, thus efficiently boosting the *COOH generation and CO₂ER performance. A designed rechargeable Zn–CO₂ battery with Cu–N₂/GN nanosheets deliver a peak power density of 0.6 mW cm^?2, and the charge process of battery can be driven by natural solar energy.     

Cu/Cu2O Interconnected Porous Aerogel Catalyst for Highly Productive Electrosynthesis of Ethanol from CO2

Use of Cu and Cu⁺ is one of the most promising approaches for the production of C₂ products by the electrocatalytic CO₂ reduction reaction (CO₂RR) because it can facilitate CO₂ activation and C C dimerization. However, the selective electrosynthesis of C₂₊ products on Cu⁰ Cu⁺ interfaces is critically limited due to the low electrocatalytic production of ethanol relative to ethylene. In this study, a novel porous Cu/Cu₂O aerogel network is introduced to afford high ethanol productivity by the electrocatalytic CO₂RR. The aerogel is synthesized by a simple chemical redox reaction of a precursor and a reducing agent. CO₂RR results reveal that the Cu/Cu₂O aerogel produces ethanol as the major product, exhibiting a Faradaic efficiency (FE_EtOH) of 41.2% and a partial current density (J_EtOH) of 32.55 mA cm⁻² in an H-cell reactor. This is the best electrosynthesis performance for ethanol production reported thus far. Electron microscopy and electrochemical analysis results reveal that this dramatic increase in the electrosynthesis performance for ethanol can be attributed to a large number of Cu⁰ Cu⁺ interfaces and an increase of the local pH in the confined porous aerogel network structure with a high-surface-area.     

Hierarchical Cross-Linked Carbon Aerogels with Transition Metal-Nitrogen Sites for Highly Efficient Industrial-Level CO2 Electroreduction

Developing highly efficient carbon aerogels (CA) electrocatalysts based on transition metal-nitrogen sites is critical for the CO₂ electroreduction reaction (CO₂RR). However, simultaneously achieving a high current density and high Faradaic efficiency (FE) still remains a big challenge. Herein, a series of unique 3D hierarchical cross-linked nanostructured CA with metal-nitrogen sites (M N, M = Ni, Fe, Co, Mn, Cu) is developed for efficient CO₂RR. An optimal CA/N-Ni aerogel, featured with unique hierarchical porous structure and highly exposed M-N sites, exhibits an unusual CO₂RR activity with a CO FE of 98% at −0.8 V. Notably, an industrial current density of 300 mA cm⁻² with a high FE of 91% is achieved on CA/N-Ni aerogel in a flow-cell reactor, which outperforms almost all previously reported M-N/carbon based catalysts. The CO₂RR activity of different CA/N-M aerogels can be arranged as Ni, Fe, Co, Mn, and Cu from high to low. In situ spectroelectrochemistry analyses validate that the rate-determining step in the CO₂RR is the formation of *COOH intermediate. A Zn CO₂ battery is further assembled with CA/N-Ni as the cathode, which shows a maximum power density of 0.5 mW cm⁻² and a superior rechargeable stability.     

Micro-Electrode with Fast Mass Transport for Enhancing Selectivity of Carbonaceous Products in Electrochemical CO2 Reduction

During electrochemical carbon dioxide (CO₂) reduction on copper electrodes in an aqueous electrolyte, one of the key challenges is the competition between hydrogen evolution and CO₂ reduction, especially under large current density. Here, micro-electrodes are designed with a copper wire as the substrate, which shows improved mass transport compared to the planar electrode. The Faradaic efficiency for C₂₊ products reaches 79% with a partial geometric current density − 77.7 mA cm⁻² on Cu₂O nanowire/micro-electrode, which is 3.7 times higher than Cu₂O nanowire/planar-electrode. The authors also designed CuO and metallic Cu with micro-electrode as substrate and observed enhanced selectivity for carbonaceous products, proving the universality of the concept. The improved activity is attributed to the fast mass transport of CO₂ to the catalytic interface and thus the suppression of hydrogen production.     

Low-Coordinated Single-Atom Catalysts Modulated by Metal Ionic Liquids for Efficient CO2 Electroreduction

Modulating the coordination environment of single-atom catalysts (SACs) is an attractive approach for maximizing the catalytic activity of single-atom centers. Currently, the synthesis of low-coordinated SACs is mainly confined to increasing the pyrolysis temperature (≥900 °C) to control C─N volatile fragments. Herein, a novel and universal strategy for the low-coordinated SACs modulation is presented using transition metal (e.g., Ni, Co, Zn) ionic liquid precursors under relatively mild temperature of 600 °C, which regulates the L-shell electronic structure and decreases nearly 50% electrophilic reactivity by ionization of 4-position N atom, thereby orienting synthesis of the SACs with metal-N3 centers. The Ni-N3 SACs exhibit exceptional CO₂ electroreduction performance of 99.7% CO Faraday efficiency with an ultra-high CO partial current density of 467.55 mA·cm⁻² as well as a CO production rate up to 10417.51 µmol·h⁻¹·cm⁻² in flow cell. The superior catalytic activity achieves over twofold increase compared with the Ni-N4 SACs prepared by non-metal ionic liquid precursors due to the lower free energy of the key intermediate *COOH and the stronger adsorption energy.     

Highly Boosted Reaction Kinetics in Carbon Dioxide Electroreduction by Surface-Introduced Electronegative Dopants

Effectively improving the selectivity while reducing the overpotential over the electroreduction of CO₂ (CO₂ER) has been challenging. Herein, electronegative N atoms and coordinatively unsaturated Ni N₃ moieties co-anchored carbon nanofiber (Ni N₃ NCNFs) catalyst via an integrated electrospinning and carbonization strategy are reported. The catalyst exhibits a maximum CO Faradaic efficiency (F.E.) of 96.6%, an onset potential of −0.3 V, and a low Tafel slope of 71 mV dec⁻¹ along with high stability over 100 h. Aberration corrected scanning transmission electron microscopy, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy identify the atomically dispersed Ni N₃ sites with Ni atom bonded by three pyridinic N atoms. The existence of abundant electronegative N dopants adjoin the Ni N₃ centers in Ni N₃ NCNFs. Theoretical calculations reveal that both, the undercoordinated Ni N₃ centers and their first neighboring C atoms modified by extra N dopants, display the positive effect on boosting CO₂ adsorption and water dissociation processes, thus accelerating the CO₂ER kinetics process. Furthermore, a designed Zn CO₂ battery with the cathode of Ni N₃ NCNFs delivers a maximum power density of 1.05 mW cm⁻² and CO F.E. of 96% during the discharge process, thus providing a promising approach to electric energy output and chemical conversion.     

Single-Atom Cadmium-N4 Sites for Rechargeable Li–CO2 Batteries with High Capacity and Ultra-Long Lifetime

The rechargeable Li–CO₂ battery shows great potential in civil, military, and aerospace fields due to its high theoretical energy density and CO₂ capture capability. To facilitate the practical application of Li–CO₂ battery, the design of efficient, low-cost, and robust non-noble metal cathodes to boost CO₂ reduction/evolution kinetics is highly desirable yet remains a challenge. Herein, single-atom cadmium is reported with a Cd-N₄ coordination structure enable rapid kinetics of both the discharge and recharge process when employed as a cathode catalyst, and thus facilitates exceptional rate performance in a Li–CO₂ battery, even up to 10 A g⁻¹, and remains stable at a high current density (100 A g⁻¹). An unprecedented discharge capacity of 160045 mAh g⁻¹ is attained at 500 mA g⁻¹. Excellent cycling stability is maintained for 1685 and 669 cycles at 1 A g⁻¹ and capacities of 0.5 and 1 Ah g⁻¹, respectively. Density functional theory calculations reveal low energy barriers for both Li₂CO₃ formation and decomposition reactions during the respective discharge and recharge process, evidencing the high catalytic activity of single Cd sites. This study provides a simple and effective avenue for developing highly active and stable single-atom non-precious metal cathode catalysts for advanced Li–CO₂ batteries.     

Electrosynthesized CuMgAl Layered Double Hydroxides as New Catalysts for the Electrochemical Reduction of CO2

In this study, new nanostructured CuMgAl Layered Double Hydroxide (LDH) based materials are synthesized on a 4 cm² sized carbonaceous gas diffusion membrane. By means of microscopic and spectroscopic techniques, the catalysts are thoroughly investigated, revealing the presence of several species within the same material. By a one-step, reproducible potentiodynamic deposition it is possible to obtain a composite with an intimate contact between a ternary CuMgAl LDH and Cu⁰/Cu₂O species. The catalyst compositions are investigated by varying: the molar ratio between the total amount of bivalent cations and Al³⁺, the amount of loading, and the molar ratios among the three cations in the electrolyte. Each electrocatalyst has been evaluated based on the catalytic performances toward the electrochemical CO₂ reduction to CH₃COOH at −0.4 V versus reversible hydrogen electrode  in liquid phase. The optimized catalyst, that is, CuMgAl 2:1:1 LDH exhibits a productivity of 2.0 mmol_CH3COOH g_cat⁻¹ h⁻¹. This result shows the beneficial effects of combining a material like the LDHs, alkaline in nature, and thus with a great affinity to CO₂, with Cu⁰/Cu⁺ species, which couples the increase of carbon sources availability at the electrode with a redox mediator capable to convert CO₂ into a C₂ product.     

Differentiating the Impacts of Cu2O Initial Low- and High-Index Facets on Their Reconstruction and Catalytic Performance in Electrochemical CO2 Reduction Reaction

Oxide-derived Cu catalysts from Cu₂O microcrystals are capable of electrochemically converting CO₂ into various value-added chemicals. However, their structural transformation and associated preferred products remain unclear, requiring further investigation. Herein, Cu₂O microcrystals with controllable low- and high-index facets exposure are fabricated to differentiate the effects of initial exposed facets on their structural reconstruction and product selectivity in electrochemical CO₂ reduction reaction. Combined in situ characterizations and theoretical investigation reveal the direct correlations of Cu₂O reconstruction and product selectivity to its initial facet exposure. The Cu₂O low-index facet, being more stable with a high energy barrier on material reduction, tends to partially maintain its original crystalline structure and larger Cu₂O particle size throughout the transformation. The derived flatter surface and limited Cu₂O/Cu interfaces result in a favorable selectivity toward 2-electron transfer products. The chemically active Cu₂O high-index facet (311) is energetically favorable to be reduced owing to the feasible protonation process, thus experiencing a drastic reconstruction with rich newly formed Cu nanoparticles and evolved fine Cu₂O grains; Such a reconstruction creates uncoordinated Cu species and abundant boundaries, benefiting charge transfer and increasing the local pH by confining OH⁻, thus leading to a high selectivity toward C₂₊ products.     

Fe?N4O?C Nanoplates Covalently Bonding on Graphene for Efficient CO2 Electroreduction and Zn?CO2 Batteries (Adv. Funct. Mater. 27/2023)

Electrochemical carbon dioxide (CO₂) reduction into value-added products holds great promise in moving toward carbon neutrality but remains a grand challenge due to lack of efficient electrocatalysts. Herein, the nucleophilic substitution reaction is elaborately harnessed to synthesize carbon nanoplates with a Fe N₄O configuration anchored onto graphene substrate (Fe N₄O C/Gr) through covalent linkages. Density functional theory calculations demonstrate the unique configuration of Fe N₄O with one oxygen (O) atom in the axial direction not only suppresses the competing hydrogen evolution reaction, but also facilitates the desorption of *CO intermediate compared with the commonly planar single-atomic Fe sites. The Fe N₄O C/Gr shows excellent performance in the electroreduction of CO₂ into carbon monoxide (CO) with an impressive Faradaic efficiency of 98.3% at −0.7 V versus reversible hydrogen electrode (RHE) and a high turnover frequency of 3511 h⁻¹. Furthermore, as a cathode catalyst in an aqueous zinc (Zn)-CO₂ battery, the Fe N₄O C/Gr achieves a high CO Faradaic efficiency (≈91%) at a discharge current density of 3 mA cm⁻² and long-term stability over 74 h. This work opens up a new route to simultaneously modulate the geometric and electronic structure of single-atomic catalysts toward efficient CO₂ conversion.     

Tailored Persistent Radical-containing Heterotrimetal-Organic Framework for Boosting Efficiency of Visible/NIR Light-driven Photocatalytic CO2 Reduction

Promoting light absorption range of photocatalysts is of great significance to improve solar light-driven photocatalytic CO₂ reduction efficiency. Herein, a new viologen-based multicomponent heterotrimetallic metal–organic framework (MOF) [Cu₃Th₆(µ₃-O)₄(µ₃-OH)₄(cpb)₁₂][Fe^III(CN)₆]₆ (IHEP-14) with an unprecedented (6, 18)-connected she-d topology is presented. Upon UV irradiation, this MOF undergoes ligand and iron photoreduction, and a single-crystal-to-single-crystal transformation to generate persistent radical-containing MOF [Cu₃Th₆(µ₃-O)₄(µ₃-OH)₄(cpb^•)₁₂][Fe^II(CN)₆]₆ (IHEP-15). This radical-containing MOF shows excellent stability without fading after at least 2 months in air. Besides extending the photoabsorption to a wider wavelength range covering from 200 to 2,500 nm, the generation of persistent radical in IHEP-15 also largely enhances its CO₂ adsorption capacity by a factor of three due to the strong affinity between π orbital of the radical and the π system of CO₂. These attributes endow IHEP-15 with excellent visible/NIR light-driven CO₂ photoreduction activity, with CO production rates under visible and NIR irradiation of 570.3 and 209.3 µmol h⁻¹ g⁻¹, respectively. Notably, the latter is a record high for NIR-induced CO production among all MOFs reported so far.     

Atomically Dispersed Silver-Cobalt Dual-Metal Sites Synergistically Promoting Photocatalytic Hydrogen Evolution

Regulating the coordination environment of single-atom sites is of high necessity to promote the catalytic performances of the photocatalysts. Herein, the preparation of atomically dispersed Co-Ag dual-metal sites anchored on P-doped carbon nitride (Co₁Ag₁-PCN) via supramolecular and solvothermal approaches is reported, which demonstrates desirable performance for photocatalytic H₂ evolution from water splitting. The optimal Co₁Ag₁-PCN catalyst achieves a remarkable hydrogen production rate of 1190 µmol g⁻¹ h⁻¹ with an apparent quantum yield (AQY) of 1.49% at 365 nm, superior to most of the newly reported metal-N-coordinated photocatalysts. Systematic experimental characterizations and density functional theoretic studies attribute the enhanced photocatalytic activity to the synergistic effect of Co-Ag dual sites with exclusive coordination configuration of Co-N₆ and Ag-N₂C₂, which enhances the charge density and promotes oriented electrons transport to the metal centers with reduced free energy barriers by facilitating the formation of H* intermediates as the key step in hydrogen evolution. This study reveals a versatile strategy to tailor the electronic structures of dual-metal sites with synergies by engineering the neighboring coordination environment.     

Boosting Industrial-Level CO2 Electroreduction of N-Doped Carbon Nanofibers with Confined Tin-Nitrogen Active Sites via Accelerating Proton Transport Kinetics

The development of highly efficient robust electrocatalysts with low overpotential and industrial-level current density is of great significance for CO₂ electroreduction (CO₂ER), however the low proton transport rate during the CO₂ER remains a challenge. Herein, a porous N-doped carbon nanofiber confined with tin-nitrogen sites (Sn/NCNFs) catalyst is developed, which is prepared through an integrated electrospinning and pyrolysis strategy. The optimized Sn/NCNFs catalyst exhibits an outstanding CO₂ER activity with the maximum CO FE of 96.5%, low onset potential of −0.3 V, and small Tafel slope of 68.8 mV dec⁻¹. In a flow cell, an industrial-level CO partial current density of 100.6 mA cm⁻² is achieved. In situ spectroscopic analysis unveil the isolated Sn N site acted as active center for accelerating water dissociation and subsequent proton transport process, thus promoting the formation of intermediate *COOH in the rate-determining step for CO₂ER. Theoretical calculations validate pyrrolic N atom adjacent to the Sn N active species assisted reducing the energy barrier for *COOH formation, thus boosting the CO₂ER kinetics. A Zn-CO₂ battery is designed with the cathode of Sn/NCNFs, which delivers a maximum power density of 1.38 mW cm⁻² and long-term stability.     

Boosting Electrochemical Reduction of CO2 to Formate over Oxygen Vacancy Stabilized Copper–Tin Dual Single Atoms Catalysts

Designing reasonable atomic structures is essential in modulating the selectivity of the valuable products produced in the electrochemical CO₂ reduction. Herein, a Cu Sn diatomic sites electrocatalyst stabilized by double oxygen vacancies on CeO_2-x is constructed, which exhibits superior electrochemical selectivity toward formate, achieving a 90.0% Faradaic efficiency at formate partial current density of 216.8 mA cm⁻² with the applied bias of −1.2 V versus REH. The experimental characterizations and theoretical calculations highlight the significance of the synergistic effect of Cu and Sn diatoms on reducing the activation energy and promoting the formation of intermediate ^*OCHO, which accounts for its high selectivity toward formate. Meanwhile, the oxygen vacancies on the CeO_2-x also play a pivotal role in manipulating the electrochemical performance and stability, which underlines the importance of regulating the electronic metal-support interaction between Cu Sn diatoms and CeO_2-x. This work demonstrates an effective method to design efficient electrochemical CO₂ reduction catalysts by modulating the surface structures of single-atoms anchored support.     

Nitrogen Vacancy Induced Coordinative Reconstruction of Single-Atom Ni Catalyst for Efficient Electrochemical CO2 Reduction

Transition metal nitrogen carbon based single-atom catalysts (SACs) have exhibited superior activity and selectivity for CO₂ electroreduction to CO. A favorable local nitrogen coordination environment is key to construct efficient metal-N moieties. Here, a facile plasma-assisted and nitrogen vacancy (NV) induced coordinative reconstruction strategy is reported for this purpose. Under continuous plasma striking, the preformed pentagon pyrrolic N-defects around Ni sites can be transformed to a stable pyridinic N dominant Ni-N₂ coordination structure with promoted kinetics toward the CO₂-to-CO conversion. Both the CO selectivity and productivity increase markedly after the reconstruction, reaching a high CO Faradaic efficiency of 96% at mild overpotential of 590 mV and a large CO current density of 33 mA cm^-2 at 890 mV. X-ray adsorption spectroscopy and density functional theory (DFT) calculations reveal this defective local N environment decreases the restraint on central Ni atoms and provides enough space to facilitate the adsorption and activation of CO₂ molecule, leading to a reduced energy barrier for CO₂ reduction.