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

Abstract TiO 2 -Cu 2 (OH)PO 4 heterojunction nanomaterials with 2–10% of Cu 2 (OH)PO 4 were synthesized by hydrothermal method. The physiochemical properties of synthesized nanomaterials were studied using XRD, FESEM, HRTEM, N 2 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% Cu 2 (OH)PO 4 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 Ti 3+ and oxygen vacancies in the TiO 2 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 Cu 2 (OH)PO 4 addition. TiO 2 heterojunction with 10% of Cu 2 (OH)PO 4 can completely reduce Cr (VI) into Cr (III) within 90 min of visible light irradiation whereas in same interval TiO 2 and Cu 2 (OH)PO 4 shows negligible and 10% reduction, respectively. Improved photocatalytic activity of TiO 2 -Cu 2 (OH)PO 4 nanophotocatalyst under visible radiation is attributed to the synergistic effect of high surface area, improved visible-NIR light absorption and formation of proper heterojunction.