Preparation of p-n heterojunction with NiWO4 and Co-based bimetallic oxide and its photocatalytic hydrogen evolution performance

Bimetallic oxides have attracted extensive attention due to their excellent photocatalytic properties. Co₂NiO₄ has good electrical activity which can effectively regulate the distribution of charge. The scanning electron microscope and transmission electron microscope images of Co₂NiO₄ showed two-dimensional uniform lamellar morphology. This kind of morphology could provide a larger specific surface area, which was conducive to improving photocatalytic water decomposing and hydrogen evolution. In addition, we combined Co₂NiO₄ with NiWO₄ to improve the conductivity of Co₂NiO₄ and the position of Fermi energy level, forming a p-n-type heterojunction, effectively promoting the interface charge transfer through the internal electric field, and inhibiting the electron–hole pair recombination. The photocatalytic hydrogen production of CN/NW-3 in the sensitized system reached 341.83 μmol for 5 h, which was 19 times that of pure Co₂NiO₄. At the same time, UV–Vis diffuse reflection and Mott–Schottky curve were used to further determine the conduction band (CB) and valence band (VB) positions of Co₂NiO₄ and NiWO₄, which formed a charge transport path with higher separation and transfer efficiency. This work highlights the high-efficient photocatalytic hydrogen production performance of CN/NW p-n heterojunction.

Graphical abstract

Co₂NiO₄ and NiWO₄ form p-n heterojunction, and the synergy between them provides a new hydrogen-producing active center for each.