Visible-light-driven hydrogen production over ZIF-8 derived Co3O4/ZnO S-scheme based p-n heterojunctions

Photocatalytic hydrogen evolution has become an alternative tool for green fuel production from water. Nevertheless, the surface texture and vast bandgap energies are still open issues before realizing the visible light application. This study yields mesoporous hexagonal ZnO nanoparticles by calcinating the obtained zeolitic imidazolate framework (ZIF-8). In addition, the ZIF-8 is combined with a Co2+ source to yield 1.0-4.0 wt% Co3O4/ZnO p-n nanoheterojunctions by the same method. The produced heterojunctions formed 35 nm of Co3O4 nanoparticles on mesoporous ZnO exteriors and exhibited very high surface areas of 1571-1691 m(2) g(-1). The addition of Co3O4 to ZnO bared more exhaustive harvesting of visible light and reduced the bandgap from 3.45 to 2.76 eV. The photocatalytic hydrogen evolution over derived Co3O4/ZnO was performed in 10% aqueous glycerol solution and hexachloroplatinic acid as hole scavenger and cocatalyst precursor, correspondingly. The 3% Co3O4/ZnO verified superior H-2 evolution of 2241 mu mol g(-1) h(-1), an 1834-times greater than the pure ZnO. The adjusted dose of this novel photocatalyst showed estimable reusability for five successive runs. The resourceful light-harvesting, minimizing bandgap and suppressing recombination explained the enhanced H-2 evolution in the occurrence of Pt cocatalyst.

Automated summary

This study successfully synthesized mesoporous hexagonal ZnO nanoparticles and Co3O4/ZnO heterojunctions through a calcination process. The addition of Co3O4 improved the H-2 evolution rate, resulting in a significantly higher production of hydrogen compared to pure ZnO. The photocatalyst also exhibited good reusability.