C₃N₄ Supported Noble Metal Hybrid Photocatalyst For CO₂ Reduction Reaction

The conversion of CO2 to CH4 by means of photocatalysis will help alleviating global warming and promote a low-carbon economy.However,the synthesis of composite photocatalysts with efficient carbon dioxide conversion efficiency is always challenged by the fact that most of the photogenerated electron-hole pairs in the semiconductor are recombined inside the semiconductor and the carbon dioxide molecules on the semiconductor surface are adsorbed and Low activation capacity.Meanwhile,since the ratio of ultraviolet light to sunlight is low,carrying out a semiconductor-supported noble metal cocatalyst based on visible light or near-infrared light is an effective way to improve the photocatalytic performance of carbon dioxide reduction.In this paper,the cocatalyst is modified by introducing noble metal with high-index faceted catalysts and twin defects engineered catalyst to improve the catalytic active sites on the surface of cocatalyst and finally enhance the performance of photocatalytic reduction of CO2.The main research contents are as follows:1.The catalytic performance of CO2 reduction to CH4 can be greatly enhanced by the introduction of cocatalysts with high-index faceted cocatalysts.In this work,PtCu alloy concave nanonanocubes with(730)facets were loaded on C3N4 nanosheets,which act as cocatalysts greatly enhancing the photocatalytic activity and selectivity in CH4 production in comparison with(100)facet enclosed PtCu nanonanocubes.As revealed by experimental characterization combined with density functional theory calculations,the(730)high-index facet has more low-coordinated metal activesites to increase the adsorption and activation of CO2,while the introduction of Cu to Pt leads to synergistic effects between the two metals for high selectivity towards the desired CH4.This work highlights the rational facet design of cocatalysts for enhanced photocatalytic performance in CO2 conversion.2.The photocatalytic performance of the carbon dioxide reduction reaction is great facilitated by Pd cocatalysts supporting double twin defects.In this work,the Pd icosahedrons with twin defects and the Pd nano-tetrahedrons without double defects all grew in situ on C3N4 nanosheets,the former effectively enhanced the photocatalytic performance of CO2 reduction to CO and CH4.The twins lines exposed on the surface of Pd cocatalyst are the highly catalytically active sites for the carbon dioxide reduction reaction.Based on the proposed mechanism,the photocatalytic activity and selectivity of CO2 are enhanced by reducing the size of Pd icosahedral cocatalyst and increasing the density of twin lines.This work proves that defect engineering on the surface of cocatalyst is a new way to achieve high-performance photocatalysis.