Controlling activation, selectivity, and transport in photocatalytic N₂ reduction to ammonia

Photocatalytic nitrogen reduction reaction (NRR), which harnesses solar energy to drive ambient N₂ fixation, has emerged as a viable supplement to the energy-intensive Haber–Bosch process—particularly for decentralized and low-carbon ammonia production. However, its implementation remains hindered by three fundamental challenges: (i) the intrinsic thermodynamic inertness of dinitrogen due to its strong triple bond and symmetric electronic configuration; (ii) the severe competition from the hydrogen evolution reaction, which thermodynamically and kinetically outpaces NRR in aqueous media; and (iii) limited mass transport of N₂ at the gas–liquid–solid interface, restricting its availability near catalytic sites. This review critically examines recent strategies to overcome these limitations within an integrated framework of activation–selectivity–transport. Advances in catalyst design, interfacial engineering, solvent systems, and device architectures are systematically analyzed. By bridging molecular insights with system-level optimization, this work provides a roadmap toward the rational design of next-generation photocatalytic platforms for sustainable ammonia production in a decentralized energy landscape.