Nickel-Doped Porous ZnO Nanosheets Functionalized with CuInS2 Nanoparticles: An Efficient Photocatalyst for Chromium (VI) Reduction

Heterojunction nanocomposites comprising Nickel-doped porous ZnO nanosheets decorated with CuInS2 nanoparticles (CuInS2/Ni-ZnO) were prepared through a facile two-step process. Compared with pure ZnO nanosheets, the Ni doping modifies the energy band structure and narrows the bandgap from 3.1 eV to 2.4 eV, thus enhancing the absorption of visible light. The production of high-quality CuInS2/Ni-ZnO nanosheets with well-matched band energy alignment facilitates effective charge transportation and separation. Benefiting from these favorable properties, the as-prepared CuInS2/Ni-ZnO heterojunction nanosheets exhibit higher photocatalytic activity for reduction of Cr (VI) than CuInS2 and Ni-ZnO in the presence of visible light. The CuInS2/Ni-ZnO-5 (2 % Ni) composite shows the best photocatalytic activity, which is 7.2 and 5.4 times higher than that of the Ni-ZnO and CuInS2. 98 % of Cr (VI) (50 mg/L) can be reduced within 25 min. Moreover, the activity and structure of the CuInS2/Ni-ZnO catalyst are maintained after five cycles. Combining theoretical calculations and experimental results, a possible photocatalysis mechanism of the CuInS2/Ni-ZnO heterojunction nanocomposites is proposed.