Advances in Co-Based Electrocatalysts for Sustainable Ammonia Synthesis: Mechanisms, Design Strategies, and Emerging Applications

Abstract

Electrochemical nitrate reduction (NO3RR) has recently attracted great interest as a promising route that couples pollutant remediation with value-added NH3 production. Compared with the nitrogen reduction reaction, NO3RR features lower activation barriers and higher solubility of nitrogen sources, though its multielectron pathways demand precise catalyst design to ensure selectivity. Among various candidates, Co-based catalysts stand out for their earth abundance, tunable electronic structures and structural diversity. This review focuses on various nanostructural engineering strategies in Co-based catalytic materials, including single-atom configurations, heterostructures, doping, alloying, and defect-engineered systems, elucidating how specific structural features regulate intermediate adsorption, reaction kinetics and overall NH3 selectivity. We also highlight the mechanistic understanding of NO3RR reaction pathways, the generation and role of active hydrogen species, and key experimental parameters that influence catalytic behavior. Furthermore, another emphasis is placed on various emerging applications such as low concentrations or real wastewater, Zn-nitrate batteries and coupled co-electrolysis for simultaneous NH₃ production and value-added chemical synthesis. Finally, key challenges and future opportunities are discussed to guide the rational design of next-generation electrocatalysts. This review seeks to provide guidance for the rational design and development of efficient nitrate reduction electrocatalysts.