Efficient solar-driven nitrogen fixation over an elemental phosphorus photocatalyst

Abstract

Photocatalytic ammonia synthesis from nitrogen (N₂) and water under ambient conditions is emerging as an intriguing alternative to the energy-consuming and CO₂-emitting Haber–Bosch process. However, photocatalytic N₂ fixation is seriously handicapped by the difficulty in N₂ activation, underlining the importance of developing efficient earth-abundant photocatalysts for the nitrogen reduction reaction (NRR). Herein, this work reported a breakthrough in the development of elemental NRR photocatalysts. Prepared by a facile sublimation–deposition method, nano-sized crystalline red phosphorous (RP) was loaded on photoinactive SiO₂ nanospheres, in which RP was modified by the in situ formed carbon material. The obtained hybrid catalyst (denoted as SiO₂/C–RP) was proved to be endowed with marked activity in photocatalytic N₂ fixation, achieving an NH₃ yield of 0.73 μmol h⁻¹ with 20 mg of catalyst in 40 mL pure water, which greatly outperformed the crystalline bulk RP. Such remarkably improved photocatalytic activity stems from the synergetic effect of the enhanced surface area, light absorption, water dispersibility and charge separation performance. This work would shed light on future design of earth-abundant, non-toxic and scalable photocatalysts for nitrogen fixation.