Tailoring the Cu Local Microenvironment to Create Formate Conversion-Desorption Equilibrium for Industrial Level...

Copper-based electrocatalysts exhibit high initial activity for formaldehyde oxidation but suffer rapid deactivation under industrially relevant current densities. While this instability has traditionally been attributed to copper self-oxidation, the fundamental origin of performance decay remains debated. Here we show that the persistent accumulation of formate intermediates rather than Cu oxidation constitutes the primary deactivation pathway, and that this bottleneck can be overcome by establishing a dynamic conversion-desorption equilibrium through local electronic microenvironment engineering. We develop an AgCu microsphere catalyst (AgCu-MSs/CF) with an optimized Ag loading of 4.1 wt.%, which achieves a current density of 1068 mA cm^-2 at 1.0 V versus RHE and operates stably up to 1.3 V versus RHE, well beyond the thermodynamic oxidation limit of Cu. Combined in situ spectroscopy and density functional theory reveal that Ag incorporation induces electron transfer from Ag to Cu, downshifting the d-band center of Cu. This electronic modulation weakens formate adsorption, thus preventing active-site blocking and ensuring the sustained catalytic activity. Leveraging this design principle, a bipolar FOR||HER electrolyzer operates stably for over 312 h. This work establishes that engineering the dynamic equilibrium between intermediate formation and removal offers a generalizable strategy to mitigate poisoning in Cu-based catalysts for complex oxidation reactions.