Boosting Photocatalytic Nitrogen Fixation via Nanoarchitectonics Using Oxygen Vacancy Regulation in W-Doped Bi₂MoO₆...

Ammonia and nitrates are key raw materials for various chemical and pharmaceutical industries. The conventional methods like Haber-Bosch and Ostwald methods used in the synthesis of ammonia and nitrates, respectively, result in harmful emission of gases. In recent years, the photocatalytic fixation of N₂ into NH₃ and nitrates has become a hot topic since it is a green and cost-effective approach. However, the simultaneous production of ammonia and nitrates has not been studied much. In this regard, we have synthesized W-doped Bi₂MoO₆ nanosheets in various molar ratios and demonstrated their potential as efficient photocatalysts for the simultaneous production of NH₃ and NO₃^- ions under visible light irradiation. It was found that one of the catalysts (BMWO0.4) having an optimal molar ratio of doped tungsten showed the best photocatalytic NH₃ production (56 μmol h^-1) without using any sacrificial agents along with the simultaneous production of NO₃^- ions at a rate of 7 μmol h^-1. The enhanced photocatalytic activity of the synthesized photocatalysts could be ascribed to oxygen vacancy defects caused by Mo substitution by a more electronegative W atom. Furthermore, density functional theory calculations verified the alteration in the band gap after doping of W atoms and also showed a strong chemisorption of N₂ over the photocatalyst surface leading to its activation and thereby enhancing the photocatalytic activity. Thus, the present work provides insights into the effect of structural distortions on tailoring the efficiency of materials used in photocatalytic N₂ fixation.