The Surface/interface Regulations On Ultrathin Photocatalysts For Efficient CO2 Reduction

Photoreduction of CO2 into useful fuels or chemicals is considered a promising method to address the crisis of fossil fuel shortage and greenhouse effect.However,the performance of CO2 photoreduction is not good enough for application,which seriously hinders its promotion in actual production.This study focuses on the problem of low efficiency and poor production selectivity in CO2 photoreduction,improving the CO2 photoreduction performance of ultrathin TiO2 nanotube-based photocatalysts through introducing defects into ultrathin TiO2 nanostructure,construction of heterostructures TiO2@BiOCl and TiO2@NH2-MIL101(Cr).The synergetic regulations of hydrogen diffusion in and out of crystal lattice,bi-metal catalytic site and interfacial effect on the CO2 photoreduction activity and production selectivity have been proposed in this work,providing novel strategies on the design,preparation and optimization of new photocatalysts for efficient CO2 reduction.Three parts of this work are listed below in detail:(1)The mechanism of hydrogen diffusion in and out of the defective ultrathin TiO2 crystal lattice improved the photoreduction activity and CH4 selectivity.During CO2 photoreduction,hydrogen diffused in and out of the ultrathin TiO2 nanostructure within abundant oxygen vacancies,producing more oxygen vacancies in the structue to narrow band gap,greatly enhancing the light utilization and the photoreduction efficiency.Meanwhile,the process also offered abundant hydrogens to the photoreduction reaction,facilitating the selective production of CH4.(2)The interface of defective ultrathin TiO2 and BiOCl lamina within Bi0 atom bridges regulated the activity and CH4 selectivity of CO2 photoreduction.The defective ultrathin TiO2@BiOCl photocatalyst was constructed,and the defective ultrathin TiO2 also permitted the hydrogen diffusion in and out of its lattice.During CO2 photoreduction,Bjo atoms were reduced at the interface of the heterostructure,reconstructing a new atomic hCLerVJtructure TiO2-Bi0-BiOCl.The directional guidance of the Bi0 atom and the capture of surface oxygen vacancy led to the gathering of electrons in the surface oxygen vacancy of TiO2,significantly enhancing the photoreduction efficiency.Meanwhile,the Bi-Ti bi-metal sites cooperated with hydrogen diffusion mechanism to enhance the hydrogenation process of the carbonaceous intermediates,boosting the selective conversion of CO2 to CH4.(3)The strong coordinated interface between ultrathin TiO2 and NH2-MIL101(Cr)improved the activity and CO selectivity of CO2 photoreduction.The loading of NH2-MIL101(Cr)on TiO2 led to abundant sites for the adsorption and reduction of CO2.Meanwhile.the strong coordination relationship between TiO2 and NH2-MIL101(Cr),formed by the binding of carboxyl in ligand at the interface of the heterostructure,improved the speration and transportation of photo-induced charge carriers significantly.Moreover,the synergetic mechanism of ligand and the surface of TiO2 nanotube led to the photocatalytic ability of the photocatalyst in the visible light range,and their special spatial coordination acceleraed the selective conversion of CO2 to CO.