Mo-W based copper oxides: Preparation, characterizations, and photocatalytic reduction of nitrobenzene

Through varying the molar ratio of Na2MoO4/(Na2MoO4 + Na2WO4) (denoted as x), a series of Mo-W based copper hydrates of CuMoxW(1−x)O4·2H2O (with x up to 0.7) and Cu3(MoO4)2(OH)2 (with x above 0.7) were prepared by a simple hydrothermal method using Cu(NO3)2, Na2MoO4, and Na2WO4 as raw materials. After a heat treatment at 400 or 500 °C for 2 h, the hydrates could be converted into CuMoxW(1−x)O4 (x = 0-0.5) and Cu3Mo2O9, (x = 0.8-1.0), respectively, except for CuMo0.7W0.3O4·2H2O (x = 0.7), a mixture of CuMoxW(1−x)O4 and Cu3Mo2O9 was produced. The experiments of photocatalytic reduction of nitrobenzene (NB) to aniline indicated the hydrates exhibited higher activities than that of their corresponding calcined sample. The mixed hydrous phase CuMo0.7W0.3O4·2H2O appeared to be the most active sample. According to the samples' band structures, the reduction of NB over prepared samples was more likely initiated by hydroxyalkyl radicals (H3CĊHOH) which originates from the oxidation of alcohol by photoinduced holes.