Fabrication of copper phthalocyanine/reduced graphene oxide nanocomposites for efficient photocatalytic reduction of hexavalent chromium

Copper(II) phthalocyanine (CuPc) and non-peripheral octamethyl-substituted copper(II) phthalocyanine (N-CuMePc) were combined with reduced graphene oxide (rGO) via a precipitation method to form CuPc/rGO and N-CuMePc/rGO nanocomposites, respectively. CuPc nanorods are distributed on rGO, and N-CuMePc exists as nanorods and nanoparticles on rGO. The Cr(VI) removal ratio of N-CuMePc/rGO exposed in simulated sunlight is 99.0% with a fast photocatalytic reaction rate of 0.0320 min, which is approximately 1.5 times faster than that of CuPc/rGO (0.0215 min) and far surpasses that of pristine phthalocyanine and rGO. As an electron acceptor, rGO can suppress the recombination of photo-induced electron-hole pairs and also can provide a large surface area for Cr(VI) removal, both of which are beneficial to the reducing capacity of the nanocomposites. The higher removal efficiency of N-CuMePc/rGO compared with that of CuPc/rGO is attributed to the higher specific surface area, higher light harvesting, higher conductivity and more negative lowest unoccupied molecular orbital level of N-CuMePc/rGO. The N-CuMePc/rGO nanocomposite shows excellent photochemical recyclability which is essential for application in wastewater treatment.