Ultralow‐Potential Photoelectrochemical Synthesis of Hydroxylamine and Oximes

Abstract The efficient and environmentally friendly synthesis of hydroxylamine (NH 2 OH) remains a challenge in sustainable chemical production. Electrochemical nitrate reduction to NH 2 OH suffers from dependence on external hydrogen sources, which often lead to the nitrite accumulation or over‐reduction of NH 2 OH to ammonia due to unbalanced hydrogenation intensity. Herein, we report the photoelectrochemical nitrate reduction to NH 2 OH (PENRH) using a bimetallic Bi‐ and Cu‐modified TiO 2 /CdS/Sb 2 (S,Se) 3 semiconductor. Under AM 1.5 G illumination, the resulting photocathode achieves a Faradaic efficiency of 91.9% and a selectivity of 92.7% at 0.3 V RHE for NH 2 OH, while effectively suppressing side reactions. In situ characterization and theoretical calculations reveal that the synergy between Bi and Cu sites optimizes the adsorption of intermediates, promotes NO 3 − protonation, and facilitates the rapid desorption of NH 2 OH, thereby preventing its over‐reduction. This system is successfully extended to the oxime synthesis by coupling in situ generated NH 2 OH with aldehydes or ketones, enabling efficient preparation of various oximes and demonstrating the broad applicability of PENRH. This work not only introduces a green photoelectrochemical approach for NH 2 OH synthesis, but also offers a new paradigm for the resource utilization of nitrate.