Structuring dual Z-scheme heterojunction and boosting surface reaction by bifunctional NiCoP modified TiO2/g-C3N4 for improving the photocatalytic activity

Low carrier separation efficiency and slow surface reaction kinetics are the main factors for restricting the development of photocatalytic technology. Construction of double Z-scheme heterojunction and deposition of cocatalyst on semiconductor are considered to be effective strategies to solve these problems. However, it is challenging to integrate dual Z-scheme heterojunction and cocatalyst in one system to enhance photocatalytic activity. In our paper, a novel ternary heterostructure TiO2/g-C3N4/NiCoP (TCNNCP) photocatalyst was constructed by depositing NiCoP cocatalyst on three-dimensional spherical TiO2/g-C3N4 surface. NiCoP in the composite can not only promote the surface reaction kinetics by reducing overpotential as a cocatalyst, but also improve the photogenerated carrier separation efficiency by constructing double Z-scheme heterojunctions with TiO2 and g-C3N4 as semiconductors. As a result, the optimized TCNNCP-2 composite exhibited a significantly improved photocatalytic hydrogen production activity of 2305.5 μmol g−1, which was 20.21 times higher than that of pure TiO2 and 3.10 times higher than that of binary TiO2/g-C3N4 composite. Additionally, TCNNCP-2 demonstrated excellent photocatalytic activity with an 86.2% removal rate for Cr(VI) within 2 h. These outstanding results can be attributed to the synergistic effect achieved through the construction of double Z-scheme heterojunctions and loading NiCoP cocatalyst, which enhance light-harvesting capability, carrier separation and transmission efficiency while promoting surface photocatalytic reactions. This research will contribute to the development of more bifunctional noble metal-free cocatalysts for efficient photocatalysis.