Revealing the synergetic effects of graphene and MoS2 on boosted photocatalytic H2 production of Mn0.5Cd0.5S photocatalyst

A new solar-light-active ternary heterojunction photocatalyst, consisting of Mn0.5Cd0.5S nanoparticles grown on 2D reduced graphene oxide (RGO)-MoS2 hybrid composite as a nonprecious and highly efficient cocatalyst has been successfully fabricated via a facile in-situ growth process. The optimized Mn0.5Cd0.5S/RGO-MoS2 nanocomposite with 2 wt% RGO-MoS2 cocatalyst displays the highest H2-evolution rate of 642.15 µmol h−1, which is about 3.75 times higher than bare Mn0.5Cd0.5S and far exceeding other composite photocatalysts, i.e., Mn0.5Cd0.5S/RGO, Mn0.5Cd0.5S/MoS2 and noble Pt-modified Mn0.5Cd0.5S. It was revealed that the dramatically improved photoactivity of the ternary Mn0.5Cd0.5S/RGO-MoS2 heterojunction photocatalyst was mainly originated from the positive cooperation between RGO and MoS2 nanosheets. The RGO nanosheets with high conductivity could serve as an electron transport bridge to collect and transfer the photogenerated electrons effectively, while MoS2 nanosheets with high electrocatalytic activity could act as an effective H2-evolution cocatalyst to facilitate the photoinduced electrons taking part in the hydrogen production reaction from water reduction, thus boosting the H2-evolution kinetics. More importantly, the RGO nanosheets could also lead to the downshift of the valence band (VB) of Mn0.5Cd0.5S, which was beneficial for the rapid oxidation of sacrificial agents and the interfacial charge transfer/separation, thereby helping to improve the photocatalytic performance.