Elucidating the unexpected electrocatalytic activity of nanoscale PdO layers on Pd electrocatalysts towards ethanol oxidation in a basic solution

Abstract

Pd-based catalysts are typically used in many applications; however, the effect of their oxide layer has not been fully investigated to date. Herein, by using experimental and theoretical approaches, we have found that the oxide layer significantly affects the electrocatalytic activity of Pd towards the ethanol oxidation reaction (EOR) in a basic solution. It alters the surface morphology and active sites of the catalyst, leading to different electrochemical kinetics and mechanistic pathways. Nanoscale PdO(101) layers on Pd(111) with the thickness of a few nanometers can strongly bind with ethanol and its intermediate species (i.e., acetaldehyde and acetic acid), leading to high current density being observed electrochemically. Also, the high surface roughness and active sites of the nanoscale PdO(101) layer can stabilize adsorbed intermediates, resulting in high autocatalytic decomposition and leading to overall productivity. This is an expected result since bulk PdO(101) is rather poor in terms of catalytic activity and productivity. Tuning the surface chemistry of metal catalysts with nanoscale oxide layers is a critical process in improving the electrocatalytic activity and productivity.