Dynamic Restructuring of Strongly Interacting Copper Single-Atom and Atomic Cluster Sites for Selective Electrosynthesis of Hydroxylamine

The ambient electrosynthesis of high-value hydroxylamine (NH 2 OH) using nitrogenous precursors has garnered significant research attention. However, uncovering the real electrocatalytic sites for the selective synthesis of NH 2 OH under operando electrocatalysis remains challenging. Herein, we report an oxygen-coordinated copper (Cu) single atoms and atomic clusters coanchored on a carbonized bacterial cellulose catalyst (Cu-SAs/ACs-CBC) via Cu–O 4 /Cu 2 coordination for the selective electrocatalytic synthesis of NH 2 OH using nitrate (NO 3 – ) as nitrogen source. The Cu-SAs/ACs-CBC exhibits significantly enhanced electrocatalytic activity toward NH 2 OH synthesis, achieving a yield rate of 273.6 ± 20.6 μmol h –1 cm –2 and a corresponding faradaic efficiency (FE) of 57.8 ± 4.4% at −0.8 V (vs RHE), whereas Cu single atoms alone are inclined to generate ammonia. Furthermore, we propose a one-step electrochemical strategy for synthesizing cyclohexanone oxime (CO) from NO 3 – and cyclohexanone using Cu-SAs/ACs-CBC, achieving a CO yield rate of 525.0 ± 45.3 μmol h –1 cm –2 with an FE of 80.5 ± 6.9% at −1.0 V (vs RHE) in a flow cell. The in situ X-ray absorption spectra reveal that Cu–O 4 /Cu 2 in Cu-SAs/ACs-CBC is electrochemically reconstituted to form Cu–C 2 O/Cu 8 as the real active site for selective NH 2 OH synthesis. Theoretical calculations further unveil that the electrochemically reconstituted Cu–C 2 O/Cu 8 site, with its synergistic effect, efficiently regulates the adsorption configuration of NO 3 –, therefore greatly improving the selectivity of NH 2 OH during electrocatalysis.