Time-dependent carbide phase formation in palladium nanoparticles

Palladium-based catalysts are widely applied for the selective hydrogenation of acetylene in acetylene/ethylene mixtures. Under reaction conditions, palladium hydride or carbide phases can be formed, which change the catalytic properties of material. In the current work, we focus on the process of carbide phase formation in supported palladium nanoparticles (NPs) exposed to acetylene and ethylene at 100 °С. The evolution of carbide phase was monitored in situ by X-ray absorption near edge structure (XANES) spectroscopy, extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray powder diffraction (XRPD). The degree of the lattice expansion determined by XRPD and EXAFS was extrapolated to obtain the saturated values, which were found to be similar for ethylene- and acetylene-exposed samples, while the rate of carbide formation was higher in the case of acetylene.