Enhanced visible light photoreduction of aqueous Cr(VI) by Ag/Bi4O7/g-C3N4 nanosheets ternary metal/non-metal Z-scheme heterojunction.

In this paper, we successfully constructed a ternary metal/non-metal nanomaterial which can synergize Z-scheme heterojunction and plasmonic metal/semiconductor for enhancing visible light photoreduction of aqueous Cr(VI). The as-formed ternary metal/non-metal nanomaterial was composed of g-C3N4 nanosheets mutual modified by Ag nanoparticles and Bi4O7. In the ternary nanomaterial, g-C3N4 nanosheets and Bi4O7 fabricated Z-scheme heterojunction, g-C3N4 nanosheets and Ag nanoparticles formed plasmonic metal/semiconductor system, synchronously. The photodeposition experiments were designed to indirect demonstrate the Z-scheme heterojunction via photocatalytic oxidation and reduction deposition reactions, AgNO3 was used as the electron acceptor and Pb(NO3)2 as the electron donor, photocatalytic reduction product and oxidation product were selectively deposited on g-C3N4 nanosheets and Bi4O7, respectively, revealing the Z-scheme heterojunction was definite formed. In addition, X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), UV-vis absorption, and Fourier-transform infrared spectroscopy (FTIR) were studied to indicate that the plasmonic metal/semiconductor system was existent in the ternary nanomaterial. The visible light photoreduction of ternary Ag/Bi4O7/g-C3N4 nanosheets was evaluated by photoreducing aqueous Cr(VI). The photoreduction results show that the ternary Ag/Bi4O7/g-C3N4 nanosheets is much higher than the pristine bulk g-C3N4 and g-C3N4 nanosheets.