On the Influence of Ag on Pd-based Electrocatalyst for Methanol Oxidation in Alkaline Media: A Comparative Differential Electrochemical Mass Spectrometry Study

In this study methanol oxidation in alkaline media was investigated in detail on Pd/C, Ag/C and PdAg/C catalysts. The electrochemical activity towards methanol oxidation reaction, the surface inhibition behavior and the CO2 current efficiency was evaluated for the catalysts by cyclic voltammetry, chronoamperometry, CO adsorbate stripping and CH3OH adsorbate stripping experiments in a differential electrochemical mass spectrometry (DEMS) flow cell setup. PdAg/C catalysts showed higher current densities, lower oxidation onset potentials and lower sensitivity to surface inhibition than Pd/C. Due to detailed studies on the CO2 current efficiencies, side products and adsorbate reactions via DEMS, novel insights into the electrooxidation of methanol on Pd/C and PdAg/C were provided. Even though Ag/C itself was not significantly active for methanol electrooxidation, it was able to promote Pd in its electrochemical activity towards methanol oxidation reaction and selectivity towards production of CO2. Additionally, PdAg/C showed lower sensitivity to catalyst poisoning compared to Pd/C.