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.