Tailoring Electronic and Morphology Features of Iron-Doped Ni2P Nanoflowers for Enhanced Ammonia Electrosynthesis in Solid Electrolyte Reactors

Abstract

Electrochemical nitrate (NO₃⁻) reduction to ammonia (NH₃) presents a promising route for both wastewater treatment and ammonia generation but still suffers from sluggish catalytic activity, insufficient mass transfer, and the reliance on high-concentration supporting electrolytes. This work reports an innovative and efficient ammonia electrosynthesis reactor by integrating a self-assembled iron-doped Ni₂P (Fe-Ni₂P/NF) nanoflower cathode with a solid-electrolyte (SE). The SE design eliminates the need for supporting electrolytes, providing a highly efficient ion-conducting pathway and enabling the direct production of NH₃ from NO₃⁻. Through tailoring the electronic and surface characteristics of Fe-Ni₂P/NF, this reactor achieves complete NO₃⁻ reduction, 96.7% NH₃ selectivity, and 81.8% faradaic efficiency with a NO₃⁻ concentration of 100 mm at a current density of 100 mA m⁻². Density functional theory (DFT) calculations reveal that phosphating and Fe doping synergistically enhance NO₃⁻ adsorption and increase the availability of active hydrogen, thus favoring NH₃ production at a low energy barrier of 0.695 eV. Additionally, the superhydrophilicity of the Fe-Ni₂P/NF nanoflower catalyst promotes mass transfer by facilitating electrolyte access and ensuring rapid gas bubble release. This study provides a sustainable and scalable method for converting NO₃⁻-laden wastewater into valuable ammonia products.