TiO2/β-C3N4 for sunlight-driven overall water splitting

β-C3N4 is one of the most difficult phases to synthesize among the C3N4 structures (α, β, cubic, pseudo cubic, and graphitic), and it has attracted marked attention because of its unique super hardness, optical properties, low density, good chemical resistance, and thermal stability. In this paper, a uniform β-C3N4 layer is successfully prepared and coated on a TiO2 nanotube substrate via a calcination treatment using ethylenediamine as the carbon nitride precursor. The as-obtained TiO2/C3N4 exhibites a promising sunlight-driven overall water splitting ability, with 1026.7 μmolH2 gcat.−1 h−1 and a 446.4 μmolO2 gcat.−1 h−1 generation rates simultaneously realized. Importantly, the turnover frequency for O2 in the photocatalytic splitting process reaches up to 4472.8 h−1 for the overall water splitting process, which is ~77.6 times that of the single β-C3N4 system (57.6 h−1) for O2 generation. In-situ Raman investigation demonstrates that N vacancy defects in β-C3N4 served as the active site for O2 generation from H2O, which is a hard nut to crack for C3N4 all the time.