Preparation Of Copper-based Nanowire Heterojunction Photoelectrocatalytic Materials And Their Application In CO₂ Reduction Reaction

In recent years,the reduction of CO2 to valuable fuels and chemicals by photocatalytic reactions has become a rapidly growing research area,and metallic copper has an unique ability in this direction,with a high hydrogen-producing overpotential and the ability to favor the binding of intermediates,thus enabling the reduction of CO2 to C2 or even more carbon products.Although copper derivatives have a low band gap,they are often susceptible to photocorrosion leading to their lack of stability in practical applications.In this paper,we mainly consider the construction of heterojunctions to protect copper derivatives,enhance light absorption and promote the separation of photo-generated electrons and holes.By introducing more stable CuFeO2,Co3O4 and LDH with large specific surface area and strong light absorption to protect the copper derivatives,reduce their photocorrosion and enhance the catalytic ability of the material,we can finally obtain more carbon products and better faradaic efficiency and selectivity in CO2RR.The main points of this paper are as follows:(1)First of all,we choose the copper-based hydroxide to prepare copper hydroxide nano wires due to the wide band gaps of copper hydroxide.We loaded LDH with narrow band gaps and good light absorption on the Cu(OH)2.The Cu(OH)2-CuNiCo-LDH heterojunction was prepared by introducing LDH with a narrower band gap and better light absorption capacity due to the wider band gap of Cu(OH)2.The UV-vis-NIR absorption spectra of the materials and the calculated tauc plots showed that the band gap of the heterojunction materials was significantly narrower than that of Cu(OH)2.The photochemical performance of the heterojunction material is also significantly enhanced,with the photocurrent density increasing from 4.2 μA cm-2 of Cu(OH)2 to 9.1 μA cm-2.In the photocatalytic CO2 reduction reaction,the faradaic efficiency of CO obtained from the heterojunction material can reach 17.74%at-1.4 V vs Ag/AgCl.(2)Considering that the band gap of CuO is narrower than that of Cu(OH)2,we chose to calcine Cu(OH)2 to obtain CuO nanowire arrays and loaded hollow dodecahedral Co3O4 derived from MOF on CuO nanowires using the impregnation method.The photocurrent density of CuO-Co3O4 heterojunctions can reach up to 233 μA cm-2.The band gap structure of the heterojunction material can be obtained by analyzing the UV-vis-NIR absorption spectra and Mott-Schottky diagrams of the material,and the CuO-Co3O4 heterojunction is enriched in electrons on Co3O4,which can have more contact with CO2 and participate in the CO2 reduction reaction,so the performance of the heterojunction is greatly improved than that of CuO,and the Faraday efficiency of ethanol in the product can reach up to reached 43.50%.(3)To add more active sites,we prepared 0D/1D CuFeO2/CuO nanowire arrays heterojunction with large specific surfaces by growing CuFeO2 in situ on the nanowires.After the formation of the heterojunction,the photocurrent density of the material is significantly higher than that of CuO at 25 μA cm-2,up to 300 μA cm-2.After fitting the AC impedance profile of the material,it can be analyzed that the charge transfer resistance of the heterojunction is also significantly reduced,which proves that the heterojunction material has a strong charge transfer capability.The analysis of the energy band diagram of the material calculated by UV absorption spectroscopy and Mott-Schottky plot shows that under the action of the electric field built into the heterojunction interface,the photogenerated holes are transferred from the valence band of CuO to CuFeO2 and the photogenerated electrons are transferred from the conduction band of CuFeO2 to CuO,and then the CO2 is reduced with high selectivity.The material also achieved good performance in the photocatalytic CO2 reduction reaction,obtaining the gaseous product CO and the liquid product ethanol,with CFO-2 showing the most excellent performance at a potential of-0.6 V vs.Ag/AgCl,obtaining a Faraday efficiency of 66.73%for ethanol and a selectivity of 94.3%for ethanol...