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

Abstract

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.

Photocatalytic fixation of nitrogen to ammonia with a Ce/S co-doped TiO2 catalyst: synergistic tuning of heterovalent metal states and oxygen vacancy defects

“…67,68 The Vo also acts as an electron capture center, offering unique sites for electron transfer and reducing electron transfer resistance, which promotes the weakening of NN bonds. 38,69 The proposed mechanism of photocatalytic N 2 fixation in TiCeOS is shown in Fig. 6.…”

“…17,73,74 Furthermore, the absence of N 2 H 4 in the reaction mixture indicates that the formation of NH 3 may be carried out through the dissociative distal pathway. 38…”

“…Hydrazine by-products were assessed using the Watt–Chrisp method, 37 while nitrates were measured via ICS and with a TU-1901 ultraviolet-visible spectrophotometer measuring absorbance at 455 nm. 38 The detailed procedure for the indophenol blue method, Nessler's reagent method, Watt–Chrisp method, and ion chromatography is described in the ESI †…”

Incorporation of Cu5FeS4 QDs with Abundant Oxygen Vacancy TiO2 QDs/TiO2 OVs: Double S-Scheme Photocatalysts for Effectual N2 Conversion to NH3 under Simulated Solar Light

“…As depicted in Figure b, the production rate of NH 3 over the Cu 5 FeS 4 , TQDs/TOVs, and TQDs/TOVs/CFS-2 photocatalysts are 2541, 3958, and 5758 μmol L –1 g –1 h –1 , respectively. In order to further appraise the efficiency of the photocatalyst, the turnover frequency (TOF) was calculated using eq . The calculated TOF value for this process over the TQDs/TOVs/CFS-2 photocatalyst was found to be 0.057 h –1 .…”

Rapid Hydrolysis Precipitation of BiOBr Nanosheets for Boosting Photocatalytic N2 Fixation

“…At present, hydrothermal synthesis is the most commonly used for catalyst synthesis, which requires massive energy and time but yields a relatively small amount of products with low purity. [35][36][37][38][39][40][41][42][43] Hence, this article proposes a novel fast hydrolysis precipitation method to synthesize BiOBr nanosheets with low energy consumption. At the same time, hydrothermal and calcination treatments are performed on the synthesized BiOBr to evaluate its photocatalytic performance.…”