Paradigm in single-atom electrocatalysts for dinitrogen reduction to ammonia

Ammonia is a fundamental chemical feedstock to produce synthetic fertilizer that is essential to feed the increasing global population. Presently, ammonia is derived from fossil fuels by the well-known Haber-Bosch process, which has high energy demands and can only be practiced on a large scale. Electrochemical ammonia synthesis provides an attractive alternative that allows distributed production with lower energy input. Single-atom catalysts (SACs) are being extensively investigated as a new class of catalysts for the electrochemical nitrogen reduction reaction, owing to the integrated merits of maximized atom utilization efficiency, tailorable metal active sites, and diverse catalytic characteristics relative to their nanoparticle equivalents. This review presents in-depth mechanistic studies and recent progress in SACs as an emerging platform for ammonia synthesis from the electroreduction of dinitrogen. Nonetheless, there are still several key challenges that must be addressed soon for these catalysts with single active sites to attain commercial success.