Oxygen vacancy-rich BiOBr microflowers for enhancing photocatalytic reduction of nitrobenzene under visible light

BiOBr has successfully been used as a photocatalyst in the selective oxidations of alcohols and amines into carbonyl compounds, however its utilization in the photocatalytic reduction reactions, especially the transfer hydrogenation of nitrobenzene (NB) to valuable organic products such as aniline, azoxybenzene, and azobenzene has rarely been reported. For the first time, we reveal the feasibility of using oxygen vacancy-rich BiOBr flower-like microsphere (BBr_OV) as a photocatalyst and hydrazine monohydrate as a green hydrogen source for such reaction. The existence of OV is probed by high-resolution transmission electron, electron paramagnetic resonance and X-ray photoelectron studies. The NB reduction activity is boosted from ~29% for pristine BiOBr microplate to ~90% for the BiOBr enriched with oxygen vacancies. Detailed characterizations disclose that the enhanced photocatalytic performance is attributed to synergistic roles of oxygen defective and hierarchical flower-like structure, endowing the BBr_OV with efficient NB adsorption/activation, enlarge surface area, improved optical absorption, and increased charge carrier generation/separation efficiency. This work not only reveals a new application of OV-rich BiOBr in the photocatalytic transfer hydrogenation of nitroarene, but also highlights the promoting catalytic effect derived from rich OV surfaces. [Display omitted]