Preparation And Performance On Copper Nanowires Gas Diffusion Electrode For Electrochemical CO₂ Reduction

Copper is the only metal that can effectively electrocatalyze the CO₂ reduction reaction to produce C₂₊products.However,the reduction reaction on copper is not highly selective for a specific product,and the reaction under high overpotential will cause a severe energy loss.Therefore,the development of more effective copper-based electrocatalysts has certain practical significance for the electric reduction of CO₂ into valuable fuels to achieve the goal of carbon neutrlity.Oxide-derived copper catalysts show industrialization prospects due to their high selectivity to C₂₊products under relatively low overpotential.In this paper,the galvanostatic deposition method is used to prepare Cu and Cu Zn alloy as precursors,and the copper nanowires gas diffusion electrode is prepared through wet oxidation and pre-reduction.At the same time,the electrocatalytic performance of copper nanowires is analyzed.Firstly,when Cu is used as the precursor,the influence of the composition of the electrodeposition bath,the electrodeposition process conditions and the electroreduction reaction conditions on the electrocatalytic performance of the copper nanowires are explored.It is determined that the pre Cu-4.5-Cu NWs catalyst prepared through deposition time of 15 min and current density of 4.5 A dm^-2 in the tartrate system exhibits high catalytic activity and stability.In a flow cell,a high faradaic efficiency of C₂H₄ formation reaches 48%at-0.8 V（vs.RHE）for 30 h.The total content of Cu⁰ and Cu⁺on the surface of the catalyst before and after the reaction is 6.9 times of Cu²⁺.The nanowires with roughed surface and formation of grain boundaries increase the opportunity of C-C coupling.Moreover,the regular structure of nanowires is more conductive to the exposure of the active part,increasing the electrochemical active surface area and the mass transfer rate,and thereby the high catalytic performance.Then,when Cu Zn alloy is used as the precursor,the effects of the deposition current density,main salt concentration ratio and total content of copper salt and zinc salt on the electrocatalytic performance of copper nanowires during the electrodeposition process are explored.The pre Cu₉₅Zn₅-0.18M-Cu NWs catalyst prepared under the conditions of a current density of 1 A dm^-2,a concentration of copper salt to zinc salt to 95:5 and a total main salt content of 0.18 mol L^-1 exhibits high catalytic performance.The selectivity of C₂H₄reaches 65%and the catalyst can continuously work for 10 h at a potential of-0.8 V（vs.RHE）.The introduction of low-content Zn in the precursor changes the arrangement of Cu,so that the growth process of Cu NWs is affected.The rough nanowires are arranged into hairball-like structure with certain interval,and Zn is completely released.The total content of Cu⁰ and Cu⁺on the surface is 2.2 times of Cu²⁺,indicating the ratio of Cu²⁺increases,which is more conducive to the formation of C₂ products on the surface/interface.Finally,based on density functional theory,the adsorption effects of different catalyst structures and pathway intermediates are calculated.Compared with the single-oriented bulk copper structure and nanowire structures,the nanowire structure with a grain boundary defect shows strong stability to the intermediate.The nanowire structure of Cu coupled with Cu O and Cu₂O further reduces the activation barrier of CO₂ and enhances the adsorption of intermediates,so that it is easy to generate C₂ products.The calculation of relative energy exhibits that in the nanowire structure with a grain boundary,*CO is easier to generate C₂H₄ through the pathway of generating*COCO and*COCOH intermediates.