Insights into Electro-Oxidative Dehydrogenation of Aldehydes on Copper Foam: The Role of Electrode Design, Side Reactions, and Substrate Properties

Abstract

A sustainable alternative to fossil-based energy sources is green hydrogen, which is produced by electrolysis, but the high energy demand of the oxygen evolution reaction (OER) limits its overall efficiency. Recent efforts aim to replace OER with low-potential anode reactions, such as the electro-oxidative dehydrogenation (EOD) of aldehydes, which simultaneously yield valuable chemical products. However, the mechanistic understanding of the EOD and the influence of catalyst structure and reaction conditions on selectivity and efficiency remain limited. Here, it is shown that the EOD of aldehydes on modified copper foam electrodes is strongly affected by electrode morphology, substrate concentration and structure, as well as electrolyte composition. It is demonstrated that increasing the electrochemically active surface area enhances current density up to a morphological diffusion limit reaching 110 mA cm−2 at 0.3 V versus reversible hydrogen electrode (RHE). Higher furfural concentrations increase current density but simultaneously promote the non-faradaic Cannizzaro reaction, thereby reducing faradaic efficiency. Lower KOH concentrations partially suppress this side reaction, though 1 M remains optimal for EOD. Substrate screening reveals that electron-rich aldehydes impede the reaction, likely by hindering intermediate formation. The findings highlight the importance of the electrode morphology and the critical balance between substrate availability and parasitic side reactions in aldehyde EOD, offering practical guidelines for catalyst design and process optimization for low-potential hydrogen production.