Faster Electron Injection and More Active Sites for Efficient Photocatalytic H₂ Evolution in g-C₃ N₄ /MoS₂ Hybrid

Herein, the structural effect of MoS₂ as a cocatalyst of photocatalytic H₂ generation activity of g-C₃ N₄ under visible light irradiation is studied. By using single-particle photoluminescence (PL) and femtosecond time-resolved transient absorption spectroscopies, charge transfer kinetics between g-C₃ N₄ and two kinds of nanostructured MoS₂ (nanodot and monolayer) are systematically investigated. Single-particle PL results show the emission of g-C₃ N₄ is quenched by MoS₂ nanodots more effectively than MoS₂ monolayers. Electron injection rate and efficiency of g-C₃ N₄ /MoS₂ -nanodot hybrid are calculated to be 5.96 × 10⁹ s^-1 and 73.3%, respectively, from transient absorption spectral measurement, which are 4.8 times faster and 2.0 times higher than those of g-C₃ N₄ /MoS₂ -monolayer hybrid. Stronger intimate junction between MoS₂ nanodots and g-C₃ N₄ is suggested to be responsible for faster and more efficient electron injection. In addition, more unsaturated terminal sulfur atoms can serve as the active site in MoS₂ nanodot compared with MoS₂ monolayer. Therefore, g-C₃ N₄ /MoS₂ nanodot exhibits a 7.9 times higher photocatalytic activity for H₂ evolution (660 µmol g-¹ h^-1 ) than g-C₃ N₄ /MoS₂ monolayer (83.8 µmol g^-1 h^-1 ). This work provides deep insight into charge transfer between g-C₃ N₄ and nanostructured MoS₂ cocatalysts, which can open a new avenue for more rationally designing MoS₂ -based catalysts for H₂ evolution.