Hierarchical porous NiO as a noble-metal-free cocatalyst for enhanced photocatalytic H2 production of nitrogen-deficient g-C3N4

Graphitic carbon nitride with nitrogen vacancies (NV-g-C3N4) as a photocatalyst has been studied in solar-driven energy conversion. However, expensive and rare noble metal co-catalysts such as Pt or Pd are required in the photocatalytic H2 evolution. Consequently, the exploration of low-cost and high-performance co-catalysts to replace expensive and rare noble metals has received more and more attention. Herein, a novel hierarchical porous NiO anchored on NV-g-C3N4 is successfully fabricated. The NV-g-C3N4/NiO photocatalysts exhibited outstanding H2 evolution rate under visible light irradiation in absence of noble metal co-catalysts. The optimized NV-g-C3N4/NiO (the mass ratio of NiO is ~ 1.7%) achieved a maximum H2 evolution rate of 170.60 μmol·g−1·h−1, exhibiting ∼ 8.3-fold enhancement as compared to that of NV-g-C3N4. NiO as co-catalyst provided more active sites for photocatalytic H2 evolution. Moreover, on the interface of NV-g-C3N4/NiO, an interface electric field is formed between NiO and host nitrogen-vacated g-C3N4, facilitating the transfer of the photogenerated electrons from NV-g-C3N4 to NiO co-catalyst, resulting in significantly promoted migration and separation efficiency of the photogenerated charge carriers.