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

Abstract 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.