Revealing the electrochemical-autocatalytic coupling mechanism of Cu-based catalysts for high-potential formaldehyde oxidation

Abstract

The electrocatalytic formaldehyde (HCHO) oxidation reaction (FOR) using copper (Cu)-based catalysts, coupled with the hydrogen evolution reaction (HER), presents a promising strategy for simultaneous hydrogen production at both the anode and cathode. However, catalyst deactivation at high potentials significantly narrows the potential window for electrocatalytic FOR, thereby limiting the achievement of high current densities. This deactivation is caused by an imbalance between the rapid electrochemical oxidation of Cu0 to Cu+/Cu2+ and the slow spontaneous chemical reduction of Cu+/Cu2+ back to Cu0, resulting in the accumulation of catalytically inactive Cu+/Cu2+ species. To overcome this limitation, a single-atom Pt/Cu catalyst supported on Cu foam (Pt1/Cu-CF) was developed to accelerate the spontaneous reduction reaction, thus successfully extending the potential window. Further investigations reveal that the spontaneous chemical reaction is intrinsically autocatalytic, as the Cu0 generated during the reaction acts as a catalyst to further accelerate the reaction. Based on these findings, we propose an electrochemical-autocatalytic coupling mechanism to elucidate the behavior of electrocatalytic FOR at high potentials. Moreover, a flow electrolyzer employing Pt1/Cu-CF as the working electrode exhibited outstanding electrocatalytic performance, achieving a current density of 1.0 A cm−2 at 1.05 VRHE and maintaining stable operation for 760 hours. This work not only provides deep insights into the mechanism of electrocatalytic FOR under high-potential conditions but also demonstrates a viable strategy for scalable bipolar hydrogen production.