High-performance NiO/g-C3N4 composites for visible-light-driven photocatalytic overall water splitting

Overall water splitting is considered as one of the most promising strategies to produce renewable energy. Based on low-cost g-C3N4, finding an abundant co-catalyst with high-performance photocatalytic activity and good stability is one of the solutions to realize overall water splitting. We designed amorphous NiO modified g-C3N4 (NiO/g-C3N4) as a photocatalyst, which could achieve efficient visible-light-driven overall water splitting without a sacrificial agent. After adjusting NiO content and calcination temperature, NiO/g-C3N4 with 1.26 wt% NiO content obtained at 300 °C shows optimal overall water splitting performance, with a hydrogen evolution rate of 1.41 μmol h−1 and an oxygen evolution rate of 0.71 μmol h−1 (λ ≥ 420 nm). NiO/g-C3N4 can be reused at least 7 times (24 h each time). The visible-light-driven overall water splitting performance of NiO/g-C3N4 should be attributed to amorphous NiO as the co-catalyst being able to promote photoinduced electron–hole pair separation, provide active sites and help to decompose generated H2O2.