Visible active novel 3D/2D SrTiO₃/Bi₂MoO₆ heterojunction catalysts for photocatalytic HER/OER and overall water splitting

Nano-sized 3D cubical strontium titanate was prepared by sol–gel technique, due to the wide bandgap of SrTiO₃, active only in the UV region. To make SrTiO₃ as visible active, the impregnation method was adopted to synthesize various weight percentages of HER active 3D SrTiO₃ and OER active and Bi₂MoO₆ nanoflakes heterojunction [x% SrTiO₃/Bi₂MoO₆ (x = 10, 30, 50, 70 & 90 SrTiO₃)]. XRD, Raman, FTIR, UV-DRS, SEM, HRTEM, and XPS instrument techniques were performed to know the physico-chemical properties of the catalysts. The rate of excitons recombination was examined through EIS and PL. The flat band potential of the bare and most active catalyst was determined by Mott-Schottky plots. The photocatalytic HER/OER performance under solar-simulating visible irradiation with and without sacrificial agents was examined for the as-synthesized catalysts. 50 % SrTiO₃/Bi₂MoO₆ catalyst exhibited the maximum rate of hydrogen (3350 μmol) and oxygen (1875 μmol) evolution at the eighth hour of the reaction. The stability of the 50 % SrTiO₃/Bi₂MoO₆ catalyst was inspected by recyclization and no apparent loss in photocatalytic efficiency of hydrogen and oxygen production was detected after five cycles. The higher electron transfer efficiency and lower exciton recombination may be ascribed to the heterojunction of 3D SrTiO₃ nanocubes and 2D Bi₂MoO₆ nanoflakes’ intimate contact with each other. The conceivable photocatalytic mechanism will be proposed by experimentally detected band gap and band edge potentials.