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

Abstract

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.