The roles of metal species supported on Fe3O4 aerogel for photoassisted 4-nitrophenol reduction and benzoic acid oxidation

Metal species deposited on catalyst supports play a significant role during the catalytic reduction or oxidation of organic compounds. In this study, we successfully prepared Ag- and Cu-supported Fe3O4 aerogels with high specific area (∼130–140 m2 g−1) and mesoporosity (pore size = 2–4 nm) and used them as catalysts for the photoassisted reduction of 4-nitrophenol (4-NP) and the oxidation of benzoic acid (BA). The Ag-supported Fe3O4 aerogels exhibited high activity for the oxidation of BA because Ag metal could attract photoexcited electrons and facilitate the production of superoxide radicals, hydroxyl radicals, and holes during the reaction. Conversely, the Cu-supported Fe3O4 aerogels could enhance the photoassisted reduction of 4-NP by forming an interfacial CuFe2O4/Fe3O4 junction to promote charge separation. Ag and Cu species on the surface of the Fe3O4 aerogel played different roles, which indicated that photoassisted catalytic performance could be tailored using different metals. Our results suggested that metal-supported Fe3O4 aerogels could be functional and promising materials for different catalytic oxidation or reduction reactions.