Formation of CH4 at the Metal-Support Interface of Pt/Al2O3 During Hydrogenation of CO2: Operando XAS-DRIFTS Study

The adsorbed intermediates on supported metal catalysts govern their catalytic activity and selectivity, although it is difficult to quantify them under the working states. We monitored the adsorbed species on Al2O3- and SiO2-supported Pt nanoparticle catalyst during hydrogenation of CO2 and elucidated the CH4-formation sites at the metal-support interface of Pt/Al2O3, by using a combination of X-ray absorption spectroscopy (XAS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) with product analysis (operando XAS-DRIFTS). Pt L-3- and L-2-edge X-ray absorption near edge structure spectra quantified the unoccupied states of Pt species, revealing that both of hydrogen and CO species adsorbed on the Pt surface of Pt/Al2O3, whereas a relatively smaller amount of hydrogen species adsorbed on Pt/SiO2. The DRIFTS and reaction results indicated that the CO species co-adsorbed with hydrogen species on the perimeter Pt sites were hydrogenated to CH4 at the interface between Pt particles and Al2O3 surface.