Enzyme-Mimetic Single-Atom Catalyst Design for Green Ammonia Synthesis

Ammonia (NH3) synthesis plays a vital role in human development, and the renewable-driven electrochemical approach offers a sustainable pathway for its green production. By drawing inspiration from and structurally mimicking natural enzymes, single-atom catalysts (SACs) demonstrate huge potential for efficiently electrolyzing molecular nitrogen or nitrate for NH3 synthesis. In this review, the latest advances in enzyme-mimetic SACs for NH3 synthesis are comprehensively summarized and highlight the significance of enzyme mimicry from four key aspects, including active sites, multi-enzyme complexes, substrate-binding pockets, and electron/proton transfer pathways. The fundamentals of SACs are first introduced, highlighting their unique advantages and outlining state-of-the-art design strategies and modification methods for performance optimization. The structural characteristics and catalytic mechanisms of nitrogenase, nitrate reductase, and nitrite reductase are then delved into, and elucidate their inspiration for SAC design. Most importantly, representative examples in enzyme-mimetic SACs for electrochemical nitrogen and nitrate reduction reactions are presented and discuss how multi-level enzyme mimicry enhances their activity, selectivity, and stability. Additionally, the key design principles of enzyme-mimetic SACs are summarized, providing guidance for the development of efficient and durable SACs. Finally, the current challenges and limitations in this field are identified and propose future research directions aimed at achieving greener and more efficient NH3 synthesis.