Highly mesoporous carbon nitride photocatalysts for efficient and stable overall water splitting

Cobalt-doped highly mesoporous g-C3N4 as efficient and stable photocatalysts for splitting water into H2 and H2O2. [Display omitted] •A one-pot salt-assisted method is used to synthesize Co-doped mesoporous g-C3N4.•The Co-mCN photocatalysts exhibit efficient and stable photocatalytic activity.•Co doping improves the charge separation efficiency and the tolerance against H2O2.•The generated H2O2 can be collected and directly applied in cyclohexane oxidation. Solar water splitting via graphitic carbon nitride (g-C3N4) has achieved extensive attention in recent years. However, g-C3N4 usually suffers from low efficiency and poor stability. Besides, the difficulty lying in the gas mixture separation remains as a big challenge. Herein, a one-pot salt-assisted method was proposed to fabricate the cobalt-doped highly mesoporous g-C3N4 (Co-mCN) photocatalysts for efficient overall water splitting into H2 and H2O2. The adjustable Co doping not only improves the charge separation efficiency, but also enhances the tolerance of g-C3N4 against H2O2 poison. The optimal production for Co-mCN catalysts is gained to be 1.82 μmol h−1 and 1.65 μmol h−1 for H2 and H2O2 respectively, while an apparent quantum efficiency (AQE) of 2.2% at 420 nm and a working life for more than 216 h are also achieved. Moreover, it is demonstrated that the produced H2O2 can be easily collected with titanium silicalite molecular sieve (TS-1) as a reusable H2O2 carrier and directly applied in catalyzing cyclohexane oxidation into cyclohexanone and cyclohexanol mixture with 100% selectivity and 0.11% conversion efficiency. This work provides a new thinking and strategy for realizing overall water splitting, manipulating the products and extending the practical applications of g-C3N4 materials in chemical industry.