Facile Synthesis Of Nanostructure Ag（Au）/Cu₂O By Galvanic Replacement Reaction And Electrochemical Reduction Of CO₂

Electrochemical reduction of CO₂to prepare fuels and chemicals is one of the important ways to achieve green conversion of CO₂.Nanostructure metal/metal oxide composites which be widely concerned as a novel of electrocatalysts,not only have the advantages of nanomaterials,but also have unique synergistic effects.In this research,Cu₂O nanospheres were used as sacrificial templates,through introducing highly active metal Ag,Au to form a nanostructure composites,the electroactive surface area is improved,and thus the electrocatalyst activity and product selectivity are ameliorated.The uniform Cu₂O nanospheres with a particle size of about 180 nm were synthesized by metal reduction in the Ethylene Glyco-Polyvinylpyrrolidone-Cetyl Trimethyl Ammonium Bromidel system,and then used as a sacrificial template,a series of Ag_2x/Cu₂O composites are fabricated through galvanic replacement reaction,in which the Ag_0.25/Cu₂O possesses a hierarchical flower-like nanostructure with the intersecting Ag nanoflakes with a thickness of 40nm encompassing the inner Cu₂O sphere.The electrochemical reduction of CO₂showed that the Faraday efficiency of CO(FE_CO)of Ag_2x/Cu₂O was significantly higher than that of Cu₂O nanospheres,with a maximum of 61%at-1.0 V（vs.RHE）.Noteworthy,novel nanostructured Ag_0.25/Cu₂O exhibits the highest CO evolution rate,up to 270μmol/mg _Ag,as a result of the hierarchical structure providing larger electroactive surface area（ESA）.Based on the Cu₂O nanospheres as a sacrificial template and the galvanic replacement reaction with Au³⁺,～270nm hollow structure Au_2x/Cu₂O composite and～300nm flower-like spherical Au_2x/Cu₂O composite were prepared.The results show that the FE_COof the flower-like spherical structure Au/Cu₂O-PVP is higher than that of Ag/Cu₂O with the same structure.In addition,the hollow structure of Au_2x/Cu₂O composite has the largest ESA.the electrochemical reduction of CO₂is optimal,and the sum of the Faraday efficiency of the CO₂reduction products is about 80%.In addition to CO and HCOOH,a deep reduction product C₂H₅OH also produced,which Faraday efficiency of Au_0.36/Cu₂O at a potential of-1.0 V（vs.RHE）is up to the maximum of 14.72%.