Development of novel TiO2-Cu2(OH)PO4 heterojunction as nanophotocatalyst for improved Cr (VI) reduction

Abstract

TiO2-Cu2(OH)PO4 heterojunction nanomaterials with 2–10% of Cu2(OH)PO4 were synthesized by hydrothermal method. The physiochemical properties of synthesized nanomaterials were studied using XRD, FESEM, HRTEM, N2 physisorption, UV–vis (DRS) and XPS. XRD indicates the formation of anatase phase. HRTEM conforms the proper heterojunction formation of diamond shaped crystalline nanoparticles with average size 20–30 nm. Addition of 10% Cu2(OH)PO4 with titania extend the light absorption to visible-NIR region and decrease the overall band gap to 2.6 eV thus enhancing the visible light absorption. The in-situ generated Ti3+ and oxygen vacancies in the TiO2 lattice along with the metallic copper at the interface results in extended visible light absorption up to NIR range and improved charge separation. Photocatalytic reduction of Cr (VI) under visible light was studied to evaluate the effect of Cu2(OH)PO4 addition. TiO2 heterojunction with 10% of Cu2(OH)PO4 can completely reduce Cr (VI) into Cr (III) within 90 min of visible light irradiation whereas in same interval TiO2 and Cu2(OH)PO4 shows negligible and 10% reduction, respectively. Improved photocatalytic activity of TiO2-Cu2(OH)PO4 nanophotocatalyst under visible radiation is attributed to the synergistic effect of high surface area, improved visible-NIR light absorption and formation of proper heterojunction. Graphical abstract TiO2-Cu2(OH)PO4 heterojunction nanophotocatalyst exhibits exceptional activity towards the reduction of Cr (VI) under visible light. Improved photocatalytic activity is attributed to the high surface area, improved visible-NIR light absorption and formation of proper heterojunction.