Constructing robust MoO2/Au/Mn0.5Cd0.5S multiple heterojunctions for improved photocatalytic hydrogen evolution: An insight into the synergetic effect of MoO2 and Au cocatalysts

Abstract

The construction of semiconductor-based nanoheterostructures toward achieving high efficient solar-to-fuel conversion is greatly limited by the insufficient electron-hole separation and the narrow spectrum range of light absorption. In this work, a novel Mn0.5Cd0.5S solid solution decorated with robust and multifunctional MoO2 and Au nanoparticles (NPs) has been constructed by a facile two-step route: the deposition of Au NPs via an in situ deposition route and further loading of MoO2via an ultrasonic chemical method. Characterization results show that both MoO2 and Au NPs can be employed as efficient cocatalytic materials to significantly promote the H2-production over Mn0.5Cd0.5S semiconductor. Particularly, the ternary 2MoO2/3Au/Mn0.5Cd0.5S nanocomposite containing 3 wt% Au NPs and 2 wt% MoO2 exhibited the optimum H2-production activity (638.83 µmol h−1) under simulated sunlight conditions, more 3.73-, 1.74- and 1.35-fold enhancement relative to pristine Mn0.5Cd0.5S, binary 3Au/Mn0.5Cd0.5S and 2MoO2/Mn0.5Cd0.5S, respectively. Mechanistic characterizations demonstrate that the positive synergetic effects between Au NPs and MoO2 can simultaneously boost the light absorption capacities, the separation efficiency of the interfacial charge carriers, and the thermodynamic performances of the hydrogen evolution reaction by strengthening the reduction ability of the photogenerated electrons and lowering the hydrogen evolution overpotential, which integratively resulted in the boosted photoactivity.