Adsorbed Hydrogen as a Site-Occupying Species in the Electrocatalytic Oxidation of Formate on Pd/C in Alkaline Medium

We investigate the mechanistic origin of oxidation of HCOO− on Pd/C in alkaline media using H/D kinetic isotope effect studies and electrochemical experiments, such as cyclic voltammetry, step-linear sweep voltammetry, and stripping voltammetry. We reveal that HCOO− is oxidized to CO2 through a direct pathway, and the oxidation of Hads is the rate determining step. The slow oxidation kinetics of Hads, which causes a site-occupying effect, suppress the oxidation of HCOO−, and a more distinct phenomenon is observed in the potential region for Hads. These observations provide clues to understanding the significant electrocatalytic activity of Pd and rational approaches for the development of more active catalysts for the oxidation of HCOO− in alkaline media.