Enhanced photocatalytic performance of persimmon cake like oxygen vacancies enriched NiO/BiVO₄ heterojunctions benefited from S-scheme interfacial charge pairs separation and transfer mechanism

Photocatalytic activity of the designed hetero-structured photocatalysts depends largely on the charge pairs transfer efficiency at the interface between the different components. Herein, NiO/BiVO4 heterojunction pho-tocatalysts were in-situ prepared using a one-pot hydrothermal method. Various techniques were used to ascertain the impact of heterogeneous structures and oxygen vacancies (OVs) on the light absorption range, energy band structure, and photogenerated carriers separation behavior of NiO/BiVO4 heterojunctions. It is found that the tight contact interfaces between NiO and BiVO4 and the establishment of internal electric field (IEF) largely promote the effective spatial separation of photoinduced carriers. OVs facilitate molecular oxygen activation and serve as reactive sites to capture photoinduced electrons, promoting the formation of center dot O-2(-). The separation of photoexcited carriers by heterojunctions and the optimization of the material energy band structure by OVs together enhance the photocatalytic activity of the catalysts. Under simulated sunlight irradiation and employing Cr(VI) as a simulated contaminant, photocatalytic performance of the synthesized catalysts was investigated. Photocatalytic reduction rate constant of Cr(VI) on NiO/BiVO4 with 2% mass ratio of Ni/Bi is found to be 15.5 times of that on the blank BiVO4. Photocatalytic activity of the catalyst was demonstrated through treatment of distillery wastewater, which confirms its strong ability to effectively photocatalytic degrade organic substances. Photoinduced charge pairs separation mechanism for enhanced photocatalytic performance of NiO/ BiVO4 heterojunction was explored based on experimental observations.