Construction Of CuBi₂O₄-based Photocathode For Photoelectrocatalytic CO₂ Reduction Reaction

The excessive consumption of fossil fuels has promoted the rapid development of material wealth and social civilization,but it has also resulted in a succession of significant ecological crises and energy security issues,such as energy shortages,surging CO2 emissions,and global warming.Photoelectrochemical CO2 reduction reaction(PEC-CO2 RR)is an important strategy to alleviate energy shortages and environmental problems.However,this method has significant drawbacks,including low light capture efficiency,sluggish kinetics,low carrier separation efficiency,and injection efficiency.CuBi2O4 is a P-type semiconductor with a narrow band gap that can efficiently utilize the visible region of the solar spectrum and is considered a promising candidate for PEC-CO2 RR.In the paper,CuBi2O4 is selected as the research object,and the above problems are effectively improved by the strategies of constructing inverse opal structure,loading co-catalyst,and constructing heterojunction.The main research contents include the following two parts:(1)In this work,the CuBi2O4 inverse opal photocathode modified with plasmonic Ag nanoparticles(CuBi2O4 IOs-Ag)was fabricated by using a sacrificing template,impregnation,and calcination method.And investigated the effectiveness of its photocatalytic carbon dioxide reduction.The CuBi2O4 IOS-Ag photocathode exhibits superior PEC-CO2 RR-to-CO performance with a Faraday efficiency(FE)of 92%at 0.2 V vs.RHE,and this value is roughly 1.6 times that of the pristine CuBi2O4 thin film.Detail characterization and experiments reveal that the exceptional three-dimensional(3D)order structure simultaneously accelerated the mass transfer rates and enhanced the light-harvesting efficiency.In addition,the introduction of Ag nanoparticles remarkably improved the surface charge distribution by forming an ohmic contact with CuBi2O4.Consequently,inhibited the carrier recombination,and improved the carrier dynamics behavior.Therefore,the CuBi2O4 IOs-Ag photocathode exhibits the excellent performance of PEC-CO2 RR.The completion of this study offers a fresh concept for the design of the PEC-CO2 RR photocathode with high carrier separation efficiency and injection efficiency.(2)The type Ⅱ heterojunction photocathode(CuBi2O4-Bi2O3)was prepared by drip coating,calcination,and chemical bath deposition,and the properties of PEC-CO2 RR and the activity sources of the photocathode were analyzed.The FECO of the photocathode is 86.03%at the lower potential(0.1 V vs.RHE),which is about 1.49 times that of the original CuBi2O4 film.The results of electrochemical tests and physical characterization show that CuBi2O4-Bi2O3 has higher light capture efficiency than CuBi2O4 and Bi2O3,and the built-in electric field increased the band bending degree,improved the surface charge distribution and the adsorption energy of intermediate products on the photocathode surface,and optimized the carrier separation efficiency.In addition,the unique coral-like structure of Bi2O3 provided abundant active sites and a large electrode/electrolyte contact area,improving the mass and electron transport during CO2 reduction.This study provides a new strategy for the design of high-efficiency photocathode through morphology regulation and construction of heterojunction.