Visible light-enhanced photothermal CO2 hydrogenation over Pt/Al2O3 catalyst

Abstract Light illumination has been widely used to promote activity and selectivity of traditional thermal catalysts. Nevertheless, the role of light irradiation during catalytic reactions is not well understood. In this work, Pt/Al2O3 prepared by wet impregnation was used for photothermal CO2 hydrogenation, and it showed a photothermal effect. Hence, operando diffuse reflectance infrared Fourier-transform spectroscopy and density functional theory calculations were conducted on Pt/Al2O3 to gain insights into the reaction mechanism. The results indicated that CO desorption from Pt sites including step sites (Ptstep) or/and terrace site (Ptterrace) is an important step during CO2 hydrogenation to free the active Pt sites. Notably, visible light illumination and temperature affected the CO desorption in different ways. The calculated adsorption energy of CO on Ptstep and Ptterrace sites was −1.24 and −1.43 eV, respectively. Hence, CO is more strongly bound to the Ptstep sites. During heating in the dark, CO preferentially desorbs from the Ptterrace site. However, the additional light irradiation facilitates transfer of CO from the Ptstep to Ptterrace sites and its subsequent desorption from the Ptterrace sites, thus promoting the CO2 hydrogenation.