Coupled electrosynthesis of formamide with ~100% carbon and nitrogen selectivity via matching cathode‒anode local pH

The electrochemical construction of C–N bonds from abundant carbon-containing and nitrogen-containing small molecules is critical for the green synthesis of amides. However, the sole conversion without C–N coupling and low-value water splitting at the counter electrode are inevitable, leading to low selectivity and faradic efficiency. Herein, we propose a coupled electrosynthesis strategy to simultaneously prepare formamide at both the cathode and anode, in which the byproducts are reused as feedstocks in the counter electrode. We design and adopt the self-supported Cu nanosheet arrays (Cu NAs) and the Pt-covered Ti sheet (Pt sheet) as cathode and anode, respectively, to match the electrolytic environments for coreduction (alkaline) and cooxidation (neutral). The abundant microchannels of the Cu NAs creates a strong alkaline microzone (0 ~ 100 nm) on the surface of the cathode, guaranteeing concurrent C–N coupling at both electrodes under neutral bulk conditions. We achieve the synthesis of formamide with ~100% carbon and nitrogen selectivity. The electrochemical construction of C–N bonds offers a sustainable route to amide synthesis, yet competing reactions that do not form C–N bonds remain unavoidable. Here, the authors report a coupled electrosynthesis strategy that simultaneously produces formamide at both the cathode and anode by recycling byproducts as feedstocks in the counter electrode, achieving nearly 100% selectivity.