Recent Progress in 2D Catalysts for Photocatalytic and Electrocatalytic Artificial Nitrogen Reduction to Ammonia

Photocatalytic and electrocatalytic N-2 reduction reactions (N2RR) for NH3 synthesis from abundant N-2, H2O, solar energy, and renewable electricity is very attractive. 2D catalysts, including photocatalysts (TiO2, Bismuth-based materials, layered double hydroxides (LDHs), carbon nitride, Fe@Graphene, MoS2 et al.) and electrocatalysts (metal, graphene, carbon, boron nitride (BN), boron carbide (B4C), black phosphorus (BP), boron, transition-metal oxide/sulfide/nitride/phosphide), have emerged as promising candidates for N2RR due to their unique physical, chemical and electronic properties. Compared with their bulk counterparts, 2D catalysts usually possess the shortened carrier diffusion pathways, higher specific surface areas and conductivity, more vacancy-type defects as well as exposed edge sites, which is beneficial to the separation of photogenerated carriers, and the adsorption and activation of N-2 molecules. This review highlights the recent progress and developments in 2D catalysts for photocatalytic and electrocatalytic N2RR for the first time. First, the prospects for photocatalytic and electrocatalytic N2RR for NH3 synthesis, and the advantages of 2D catalysts are briefly introduced. Second, the application of 2D catalysts for N-2 photoreduction and electroreduction is systematically summarized. Finally, the major challenges and future outlook of this burgeoning area are provided.