A novel Ag deposited nanocoordination polymer derived porous SnO2/NiO heteronanostructure for the enhanced photocatalytic reduction of Cr(VI) under visible light

The fabrication of a novel porous Ag deposited SnO2/NiO (Ag/SnO2/NiO) heteronanostructure for the photoreduction of toxic aqueous Cr(VI) to non-toxic Cr(III) is reported. The material is prepared by depositing metallic Ag nanoparticles into the SnO2/NiO heteronanostructure by the reduction of Ag+ under UV irradiation. The SnO2/NiO heteronanostructure is obtained by a facile solid-state transformation of the novel nanocoordination polymer (NCP). The prepared Ag/SnO2/NiO is characterized by different techniques such as PXRD, XPS, EDX, FESEM, TEM, HRTEM, BET, UV-Vis DRS and PL measurements. The PXRD and XPS studies confirm the formation of a Sn(IV) state of SnO2 in the heterostructure. TEM images reveal the spherical morphology of Ag nanoparticles with an average particle size of 15 nm, and hexagonal shaped SnO2 and NiO with an average particle size of 10 and 5 nm in Ag/SnO2/NiO, respectively. The incorporation of Ag enhances visible light absorption and higher electron-hole separation of Ag/SnO2/NiO by Surface Plasmon Resonance (SPR). Besides, the material exhibits a high surface area and porous nature, which facilitates the effective photocatalytic reduction of toxic aqueous Cr(VI) to non-toxic Cr(III) under visible light. Furthermore, the photocatalytic reduction of Cr(VI) is optimized under different conditions. The photostability of Ag/SnO2/NiO is tested up to five successive runs indicating its promising applications for wastewater treatment. Finally, a photocatalytic mechanism is proposed for the reduction of aqueous Cr(VI) over Ag/SnO2/NiO under visible light.