Construction Of Active Sites On Cu Based Nanomaterials And Their Electrocatalytic Mechanism For Carbon Dioxide Reduction

To maintain the global CO₂ balance,various technologies of decarbonization,carbon sequestration,and carbon recycling have been developed.Among them,CO₂ reduction reaction（CO₂RR）is a more attractive strategy since it can simultaneously meet the demands for reducing CO₂ emissions and producing valuable chemicals.In recent years,electrocatalysis has stood out from various novel technologies for several reasons.First,the reaction rate and selectivity can be well controlled via adjusting applied potential.Second,CO₂ can be directly reduced to a wide variety of C₁/C₂ products in a mixture or pure form.Furthermore,the electrochemical technology can utilize a wide range of renewable electricity sources without any new CO₂ generation.CO₂RR has broad commercial application value.However,several remaining technological barriers restrict its commercialization,such as slow kinetics,high overpotential,and insufficient stability.Accordingly,the development of stable electrocatalysts with high selectivity and activity becomes the core issue of this technology.According to the principle of nano-catalyst interface design,a series of oxide derived copper catalysts with different surface/interface structures are accurately constructed around the above problems.Combing experiments with theoretical calculations reveal the structural-activity relationship between surface structure and catalytic behavior.The main research contents and conclusions are as follows:（1）The Cu⁺/Cu⁰ interface in the Cu-based electrocatalyst is essential to promote the electrochemical reduction of carbon dioxide（ERCO₂）to produce multi-carbon hydrocarbons and alcohols with high selectivity.However,due to the high activity of Cu⁺/Cu⁰ interface,it is easy to be oxidized in the air.How to control and prepare Cu-based electrocatalyst with abundant and stable Cu⁺/Cu⁰ interface in situ is a huge challenge.Here,combined with density functional calculation（DFT）and experimental studies,we found that the trace halide ions（Br^-ion）adsorbed on Cu₂O can slow the reduction kinetics of Cu⁺→Cu⁰,which allowed us to in-situ well control the synthesis of CuO-derived electrocatalyst with rich Cu⁺/Cu⁰ interfaces.Our Cucatalyst with a rich Cu⁺/Cu⁰ interface exhibits excellent ERCO₂ performance.Under the operation potential of-0.98V vs.RHE,the Faraday efficiency（FE）of C₂H₄ and C₂₊products are 55.8%and 75.7%,respectively,which is about 16%higher than that of CuO-derived electrocatalysts that do not use halide ions.The high₂₊comes from the improvement of the coupling efficiency of reaction intermediates such as CO-CO,which is proved by DFT calculations,and the suppression of hydrogen evolution reaction.（2）Taking CuO-CuI electrocatalysts as an example,we focused on studying the structural evolution,interactions,and activity sources of the two components in the electrocatalyst during the CO₂RR under high current conditions.By partially oxidizing commercial CuI,a large amount of I ions are retained,forming an iodine rich environment that inhibits the electrochemical reduction of CuO,thereby obtaining stable active Cu⁰/Cu⁺species.The residual iodine species are adsorbed on the surface of Cuas electronic regulators,promoting the conversion of CO₂ to C₂H₄.Meanwhile,reports have shown that local iodine induced Cu⁰/Cu⁺sites can significantly reduce the energy barrier of C-C coupling,thereby improving the selectivity of C₂₊.Thanks to the dual regulatory effect of this adaptive structural evolution,CuI-400℃-60min catalyst exhibited a high Faraday efficiency of approximately 69.7%and a partial current density of approximately 284 m A/cm² for C₂₊at-1.32 V vs.RHE.（3）We develop an effective Cu-O-C interface effect for enhancing the electrocatalytic CO₂RR of C₂₊products.The Cu-O-C interface is obtained by electrostatic adsorption of graphite oxide quantum dots onto the surface of CuO NSs,and then in-situ electroreduction synthesis of CuO-C（O）hybrids.Owing to abundant Cu-O-C interfaces in the CuO-C（O）hybrid,the CuO nanosheets were topologically and selectively transformed into metallic Cunanosheets exposing Cu（100）facets,Cu（110）facets,Cu[n（100）×（110）]step sites and Cu⁺/Cu⁰ interfaces during the electroreduction step.The reduced CuO-C（O）catalyst delivered very high Faradaic efficiencies（FE）to C₂₊products,reaching as high as 77.4%（ethylene FE～60%）at 500 m A/cm²,while also showing excellent long-term stability for CO₂RR at such industrially-relevant current densities.In situ ATR-SEIRAS and DFT simulations demonstrated that abundant Cu⁺species and Cu⁰/Cu⁺interfaces in the reduced CuO-C（O）catalyst improved the adsorption and surface coverage of*CO on the Cucatalyst,thus facilitating C-C coupling reactions leading to C₂₊products.