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

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/Al 2 O 3 prepared by wet impregnation was used for photothermal CO 2 hydrogenation, and it showed a photothermal effect. Hence, operando diffuse reflectance infrared Fourier-transform spectroscopy and density functional theory calculations were conducted on Pt/Al 2 O 3 to gain insights into the reaction mechanism. The results indicated that CO desorption from Pt sites including step sites (Pt step ) or/and terrace site (Pt terrace ) is an important step during CO 2 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 Pt step and Pt terrace sites was −1.24 and −1.43 eV, respectively. Hence, CO is more strongly bound to the Pt step sites. During heating in the dark, CO preferentially desorbs from the Pt terrace site. However, the additional light irradiation facilitates transfer of CO from the Pt step to Pt terrace sites and its subsequent desorption from the Pt terrace sites, thus promoting the CO 2 hydrogenation. Light illumination and temperature affected CO coverage during CO 2 hydrogenation in different ways, offering a new pathway for improving the thermal catalysis.