Preparation Of Self-supported Nanoporous AuCu Electrode For Efficient Electrochemical CO₂ Reduction

Electrocatalytic reduction of carbon dioxide is an effective method to solve the problem of the greenhouse effect.This reaction is widely studied because of using renewable electricity as an energy source at normal temperature and pressure to reduce CO₂ to value-added chemical raw materials or fuels.In this field,copper has attracted much attention owing to its low price and ability to reduce CO₂ to a variety of hydrocarbon products.However,pure copper cannot be widely used in the electrocatalytic reduction of carbon dioxide due to its high overpotential,low selectivity,and serious hydrogen evolution.In this work,nanoporous Au₃Cu and AuCu₃ catalysts were successfully synthesized by a mild oxidative etching method,and showed high activity and selectivity for carbon monoxide(CO)in the electrocatalytic reduction of carbon dioxide(ECR).The details are as follows:(1)Etching Au₂₀Cu₈₀ alloy with Fe³⁺solution at room temperature to obtain nanoporous Au₃Cu.HRTEM,XPS and EXAFS revealed that the surface of the synthesized nanoporous Au₃Cu is rich in gold and has an unsaturated coordination environment,which provide fruitful active sites for ECR.It can be directly used as a working electrode in the ECR.At-0.7 V(vs.RHE)potential,exhibiting a high Faraday efficiency(FE)of 98.12%relative to CO,which is 1.47 times that of single nanoporous Au.Density functional theory(DFT)and Hirshfeld charge distribution show that nanoporous Au₃Cu has the lowest*COOH adsorption free energy and lower CO desorption energy.This provides a convenient method for surface engineering design on self-supported nanoporous metals,and is expected to be applied in energy catalysis.(2)By changing the concentration of Fe³⁺,a monolithic nanoporous core-shell AuCu₃@Au with intermetallic Au-Cu core and Au-rich shell was successfully synthesized.Under the condition of-0.6 V(vs.RHE),the obtained nanoporous electrode has a FE(CO)of 97.27%,and the partial current density of CO is 5.3 m A cm^-2.Compared with Au₃Cu,it not only reduces the cost,but also maintains the high activity and high selectivity of CO.Moreover,a 23 cm-long nano-porous AuCu₃@Au bulk electrode with good ductility was obtained.The electrode displayed an active current of 37.2 m A at-0.7 V vs.RHE,which promotes the industrialization of ECR.