Metal-Free Single Atom Catalyst for N₂ Fixation Driven by Visible Light

Solar nitrogen (N₂) fixation is the most attractive way for the sustainable production of ammonia (NH₃), but the development of a highly active, long-term stable and low-cost catalyst remains a great challenge. Current research efforts for N₂ reduction mainly focus on the metal-based catalysts using the electrochemical approach, while metal-free or solar-driven catalysts have been rarely explored. Herein, on the basis of a concept of electron "acceptance-donation", a metal-free photocatalyst, namely, boron (B) atom, decorated on the optically active graphitic-carbon nitride (B/g-C₃N₄), for the reduction of N₂ is proposed by using extensive first-principles calculations. Our results reveal that gas phase N₂ can be efficiently reduced into NH₃ on B/g-C₃N₄ through the enzymatic mechanism with a record low onset potential (0.20 V). Moreover, the B-decorated g-C₃N₄ can significantly enhance the visible light absorption, rendering them ideal for solar-driven reduction of N₂. Importantly, the as-designed catalyst is further demonstrated to hold great promise for synthesis due to its extremely high stability. Our work is the first report of metal-free single atom photocatalyst for N₂ reduction, offering cost-effective opportunities for advancing sustainable NH₃ production.