Facile synthesis of multi-layer Co(OH)₂/CeO₂-g-C₃N₄ ternary synergistic heterostructure for efficient photocatalytic oxidation of NO under visible light

In this work, we report a one-step synthesis of ternary Z-scheme Co(OH)₂/CeO₂-g-C₃N₄ (CoCe-CN) heterostructure via hydrothermal method. Owing to the modification of Co(OH)₂ and CeO₂, the existence of Co(OH)₂ as an electron acceptor-donor center between CeO₂ and g-C₃N₄ accelerates the electron transfer and provides extra OH^- reaction pathway for photocatalytic oxidation of NO. As a result, 50CoCe-CN (Co and Ce accounting for 25% mass ratio separately) achieved a 53.5% conversion efficiency of NO at 600 ppb concentration, which is 1.82 times that of g-C₃N₄ under visible light. The results of the DFT analysis and element distribution of cobalt and ceria provide convincing evidence supporting the existence of a novel multi-layer structure in the CoCe-CN photocatalyst. This structure involves the loading of CeO₂ and Co(OH)₂ on the g-C₃N₄ surface, and Co(OH)₂ as a co-catalyst introduced between CeO₂ and g-C₃N₄ realizes the synergy between CeO₂ and Co(OH)₂ which further improve the photocatalytic properties. The higher photocatalytic efficiencies observed in the CoCe-CN photocatalysts compared to those containing only cobalt (Co-CN) or ceria (Ce-CN) provide further evidence of the synergistic effect of these two elements. This work demonstrates a more efficient and effective ternary photocatalytic system, with greater practical potential for photocatalytic oxidation of NO.