Catalytic hydrodechlorination is a useful technique to upgrade chloromethanes due to its mild operation conditions. Our previous kinetic experiments revealed that the introduction of Ag to the Al2O3-supported Pt catalyst resulted in a significant enhancement of both the catalytic activity and the selectivity towards CH2Cl2 during CHCl3 hydrodechlorination. This proposal aims to utilize in-situ X-ray absorption spectroscopy (XAS) to investigate the coordination environments and electronic properties of both Pt and Ag at different reaction temperatures and times in real reaction conditions. The objective is to identify the active sites of the PtAg/Al2O3 catalyst and clarify the synergistic effect of Pt and Ag in enabling the improvement of catalytic activity and high selectivity towards CH2Cl2 in the CHCl3 hydrodechlorination reaction.