Electrochemical nitrate reduction to ammonia by non-noble metal single-atom catalysts: bridging waste remediation and sustainable hydrogen storage

Abstract

Ammonia plays a pivotal role in agriculture and industry, while being increasingly viewed as a carbon-free hydrogen carrier. Over the past decade, electrochemical nitrate reduction to ammonia has emerged as a promising green route, bridging waste remediation and effective hydrogen storage. In this context, non-noble metal single-atom catalysts (SACs) are particularly attractive due to their tunable electronic structure and high reaction selectivity. This review provides a timely and comprehensive overview of electrochemical nitrate reduction to ammonia by non-noble metal SACs. In this review, the principles and reactor configurations for electrochemical nitrate reduction are examined and then the synthesis strategies and characterization techniques for non-noble metal SACs are critically summarized. Recent advances in utilizing non-noble metal single-atom catalysts for electrochemical nitrate reduction to ammonia are systematically assessed in terms of NH₃ yield, Faraday efficiency, selectivity, and underlying mechanisms. Finally, the persistent challenges and future perspectives are discussed, with the aim of guiding the rational design of non-noble metal single-atom catalysts towards highly efficient electrochemical nitrate reduction to ammonia.