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

This study develops boron-doped amorphous bismuth metallene arrays for efficient nitrate-to-hydroxylamine electroreduction. The B-induced p-sp orbital hybridization and amorphous structure modulate the electronic configuration and increase active site density, thus optimizing intermediate adsorption and H* generation while lowering the energy barrier of the potential determining step. The catalyst achieves 85.3% NH₂OH Faradaic efficiency (FE) at −0.4 V versus RHE, which further rises to nearly 100% under pulsed potential operation, surpassing most reported systems.

Abstract

Electrochemical hydroxylamine (NH₂OH) synthesis from NO_x 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-NH₂OH 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.

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