Sustaining Dynamic Cu Surface Reconstruction in Formaldehyde Oxidation Coupled with a Mechanically Robust Substrate-Supported Electrode Design

The electrocatalytic formaldehyde oxidation reaction (FOR) on copper–based catalysts enables anodic hydrogen production and serves as an alternative to the oxygen evolution reaction by lowering the voltage requirement for water electrolysis. However, Cu–based electrocatalysts are constrained by a narrow operating potential window that limits attainable current densities, while insufficient long–term stability further restricts practical application. Herein, simultaneous enhancement of activity and stability is achieved by fabricating rough copper nanosheets on nickel foam (Cu–NF). The rough copper nanosheets increase the density of accessible active sites, enabling current densities up to 500 mA·cm −2 at 0.45 V vs RHE within the limited operating potential window. Moreover, the mechanically robust nickel foam scaffold helps preserve electrode integrity during prolonged anodic operation, while the dynamic Cu 0 /Cu+ surface evolution in the catalytic layer supports sustained activity, enabling stable operation for over 200 h. This work provides a general design guideline for achieving a balanced improvement in activity and durability of copper–based electrodes for formaldehyde oxidation. OH − –assisted Cu surface evolution, sustained by formaldehyde-driven Cu 0 /Cu + cycling, stabilizes active Cu sites during formaldehyde oxidation, while a mechanically robust nickel foam substrate preserves electrode integrity, enabling high current density and long-term stable bipolar hydrogen production.