Local Acidic Microenvironments Enhanced Anodic Formamide Electrosynthesis over Isolated Pd Sites

Electrocatalytic C─N oxidative coupling of methanol and ammonia enables sustainable formamide synthesis under ambient conditions. However, the poor C─N coupling selectivity and limited Faradaic efficiency hinder practical application. As the critical step involves nucleophilic attack of NH₃ on in situ generated *CH₂O intermediates, enhancing *CH₂O electrophilicity while suppressing over-oxidation is essential. Herein, Pd single atoms anchored on MnO₂ nanoarrays achieve state-of-the-art Faradaic efficiency (62.6%) and carbon selectivity (80.2%) for anodic formamide synthesis. In situ characterization and theoretical simulations reveal dual enhancement mechanisms: Isolated Pd sites adopt end-on *CH₂O adsorption to expose the electrophilic carbon, while the MnO₂-induced acidic microenvironment enhances *CH₂O electrophilicity via oxygen-atom protonation. This synergy accelerates nucleophilic attack by NH₃, enabling efficient C─N coupling.