Photofixation of N2 to ammonia utilizing Ni@TPP–HPA nanocomposite under visible-light illumination

Abstract

The production of ammonia as an important raw material in the chemical, agricultural, and food industries has been always a significant concern. However, conventional ammonia production methods require high energy consumption and costs. The photocatalytic rotes use green light sources and cost-effective photocatalysts to obtain ammonia from water under aerobic conditions and preventing production of greenhouse gases in the environment. To produce an effective heterogeneous catalyst, a new tetraphenylporphyrin–heteropolyacid (TPP–HPA) nanohybrid material is synthesized and loaded onto Ni nanoparticles in this work. Then, FE-SEM, EDS, XRD, and FT-IR analyses were applied to characterize the prepared nanohybrid material Ni@TPP–HPA. After that, the new inorganic–organic nanohybrid photocatalyst was introduced as an effective, environmental friendly, and recyclable mediator for N₂ photofixation. The results showed that Ni@TPP–HPA is a good photocatalyst for the N₂ fixation reaction and can be easily recycled without losing its activity for at least five runs. The Ni@TPP–HPA nanocomposite demonstrated the maximum ammonia generation by 2760 μmol L⁻¹ g⁻¹ under mild conditions when using methanol as a hole scavenger. Additionally, effects of solvent type, temperature, reaction time, irradiation source, solution pH, and other electron scavengers on the rate of NH₄⁺ production were investigated and discussed.