Synergistic Modulation of Intermediate Adsorption and Active Hydrogen Supply Enable Pulsed Nitrate-to-Hydroxylamine Electroreduction with Nearly 100% Faradaic Efficiency.

Electrochemical hydroxylamine (NHOH) synthesis from NO under ambient conditions presents a sustainable alternative to energy-intensive industrial methods, but its selectivity remains limited by unbalanced active hydrogen (H*) supply and intermediate adsorption. Herein, we develop boron-doped amorphous Bi metallene arrays for efficient nitrate-to-NHOH electroreduction. In situ spectroscopy and theoretical calculations reveal that the amorphous structure and B-induced p-sp orbital hybridization modulate the electronic structure, optimizing intermediate adsorption while enhancing H* generation. These synergistic effects collectively reduce the energy barrier of the potential-determining step, significantly improving catalytic activity and selectivity. The catalyst achieves an NH₂OH Faradaic efficiency (FE) of 85.3% at -0.4 V versus reversible hydrogen electrode (RHE). By employing a pulsed potential strategy, the FE further increases to nearly 100%, surpassing most reported counterparts. This work not only proposes a novel catalyst design leveraging amorphous engineering and orbital hybridization but also demonstrates the efficacy of pulsed electrolysis in steering reaction pathways for electrosynthesis.