Fabrication Of Cu Sn Bimetallic Electrodes And Study On Electrocatalytic Performance Of CO₂ Reduction

Electrochemical CO₂ reduction（CO₂RR）,which can convert CO₂ into various value-added chemicals in a mild way using renewable electricity,provides an appealing approach to remedying the issues of global warming and energy crisis.In this dissertation,a series of Cu Sn bimetallic catalytsts featuring unique hierarchical structures are successfully fabricated for highly efficient CO₂RR via integrating active Sn component with commercial Cu foam.On the basis of multiple characterizations and density functional theory（DFT）calculation,in-depth understanding on the enhanced CO₂RR performance is obtained.This dissertation mainly includes the following two parts:1.Cu foam supported Cu bundles are first fabricated via chemical oxidation and electroreduction treatments,and then employed as the substrate for chemical deposition of Sn O species.The abundant Sn O active sites and the unique structure endow the Cu foam-Sn O composite electrode with excellent electrocatalytic activity in CO₂RR.As a result,a partial current density of C₁ products as high as 128.6 m A cm^-2 with a Faradaic efficiency of 80.4%is achieved at-1.2 V vs.RHE.2.Cu foam supported Cu Sn alloy nanowires are successfully constructed via a multi-step strategy comprising chemical oxidation,annealing and electrochemical treatments.The hierarchical Cu Sn alloy electrode can simultaneously achieve cathodic CO₂ reduction and anodic methanol oxidation（MOR）for formic acid production.Operando Raman spectra,H/D isotope experiment and DFT calculation results reveal that the Sn atoms in Cu Sn alloy serve as active sites for the adsorption and activation of CO₂,whereas the adjacent Cu atoms can facilitate the activation of H₂O for H supply in CO₂ hydrogenation.This synergestic catalysis greatly reduces the energy barriers during the generation of formic acid,thereby promoting CO₂reduction.As a result,a partial current density for formic acid up to 140.6 m A cm^-2with a Faradaic efficiency of 87.3%is delivered by the optimized Cu Sn electrode at-1.4 V vs.RHE,corresponding to a formic acid formation rate of 2615μmol h^-1cm^-2.For MOR,the Faradaic efficiencies of formic acid can be kept above 95%in a wide potential window ranging from 1.4 to 2.0 V vs.RHE.Compared with oxygen evolution reaction（OER）,the overpotential is significantly reduced by 290 m V to achieve a current density of 200 m A cm^-2.As a step further,the Cu Sn alloy electrode is employed concurrently as both the cathode and anode in a two-electrode setup comprising CO₂RR-MOR couple.A current density of 100 m A cm^-2 is achieved under a cell voltage of 3.23 V,which is 610 m V lower than that of the CO₂RR-OER couple.Remarkably,high Faradaic efficiencies of 93.2%and 99.1%are obtained respectively for the CO₂RR and the MOR at a current density over 100 m A cm^-2 on Cu Sn alloy electrode.This work provides an appealing strategy for highly efficient formic acid production by the utilization of both anodic and cathodic half reactions.