Bimetallic nitrogen-doped carbon electrocatalysts for nitrate-to-ammonia conversion: synthesis strategies, catalytic mechanisms, and perspectives

Abstract

Nitrate pollution in groundwater poses significant environmental and health risks. Conventional nitrate removal technologies are often inefficient and incomplete, whereas the electrochemical nitrate reduction reaction (NO₃RR) offers a promising alternative by simultaneously removing nitrate pollutants and producing value-added ammonia. Among emerging NO₃RR electrocatalysts, bimetallic nitrogen-doped carbon-based (BM-NCs) materials have demonstrated outstanding Faradaic efficiency (FE), ammonia production rate, and long-term stability. These advantages arise from the synergistic interplay between nitrogen doping and bimetallic components, which collectively enhance electrical conductivity, promote nitrate adsorption, and optimize reaction kinetics and product selectivity. Notably, bimetallic combinations such as Cu-Ni, Co-Fe, Fe-Mo can effectively tune charge redistribution and interfacial electronic structures, thereby improving catalytic performance. This review systematically summarizes recent advances in BM-NCs for NO₃RR, with emphasis on synthesis strategies, structure-activity relationships, and reaction mechanisms. The dual role of nitrogen doping in enhancing electronic conductivity and promoting interfacial charge transfer is highlighted, together with mechanistic insights into bimetallic synergy, including charge redistribution and stepwise catalytic pathways, as revealed by experimental characterization and theoretical calculations. By establishing clear synthesis-performance correlations, this review demonstrates how controlled synthetic strategies modulate bimetallic dispersion and nitrogen coordination environments to optimize NO₃RR activity and selectivity. Finally, current challenges and future opportunities are discussed to guide rational catalyst design and accelerate the practical application of BM-NC electrocatalysts in nitrate remediation and sustainable ammonia synthesis.