Direct Z-scheme-based novel cobalt nickel tungstate/graphitic carbon nitride composite: Enhanced photocatalytic degradation of organic pollutants and oxidation of benzyl alcohol

Designing a photocatalyst with strong redox ability and broad absorption of visible light is challenging in the field of photocatalysis. In this study, a series of novel Z-scheme-based CoxNi1-xWO4/g-C3N4 (x = 0, 0.2, 0.5, 0.8 and 1) photocatalysts are synthesized with a view to increasing their redox abilities and improve their photo catalytic activities under broad absorption of visible light. The physicochemical properties are investigated, and the data show that an intimate stable heterojunction is formed between the bimetallic tungstate (CoNiWO4) and g-C3N4 (g-CN). Bifunctional properties of the synthesized catalysts are assayed by studying the decomposition of rhodamine B (RhB), bisphenol A (BPA), and selective conversion of benzyl alcohol (BA) to benzaldehyde (BDA). The composite material containing 1:1 molar ratio of Co/Ni shows the highest activity towards the degradation of RhB (99.8%) and BPA (99.32%), and the conversion of BA to BDA (86.96%), each at 1 g/L-dose. The well matched band structure between CoNiWO4 and g-CN facilitates the formation of a Z-scheme charge transfer path, which prolongs the life time of the photoinduced charge carriers with high redox power, thus enhancing the photocatalytic activity. An intensive study of the mechanism proves that the degradation is driven by the hydroxyl ((OH)-O-center dot) and superoxide (O-center dot(2)-) radicals, indicating that CoNiWO4/g-CN follows the Z-scheme charge transfer pathway. The current study has shown the superior photocatalytic activity among all tungstate-based hybrid photocatalytic materials for the degradation of complex organic pollutants, and selective transformation of BA to BDA. The findings in this study provide a new direction to the development of an efficient direct Z-scheme Co-Ni bimetallic tungstate-based photocatalyst for several redox reactions, especially mineralization of recalcitrant aqueous organic compounds.

Automated summary

A series of novel Z-scheme-based CoxNi1-xWO4/g-C3N4 photocatalysts were synthesized to enhance redox abilities and improve photocatalytic activities. The composite material showed high efficiency in degrading complex organic pollutants and selectively transforming benzyl alcohol to benzaldehyde through a Z-scheme charge transfer pathway. The results provide a new direction for the development of efficient Co-Ni bimetallic tungstate-based photocatalysts for various redox reactions.