One-pot synthesis of a CdS–MoS2 / CNTs nano-composite for photocatalytic hydrogen production under visible light

The need to meet growing energy demands of global society in a sustainable fashion requires the development of techniques and processes to reduce dependence on fossil fuels and transit to renewable energy sources. Environmentally benign technologies for alternative fuel production in the form of hydrogen can be developed via heterogenous photocatalysis, a process based on utilization of solar energy. To this end, a cadmium sulfide (CdS) based photocatalyst was developed, doped with MoS2 in a one-pot solvothermal synthesis technique, and coupled with multi-walled carbon nanotubes (MWCNTs) as a carbonaceous support. The material exhibiting the highest rate of hydrogen evolution, CM5C3, involved a MWCNTs loading of 3% and MoS2 loading of 5%. Compared to pure CdS synthesized with the same adapted procedure, the 3% CNT loading improved the rate of hydrogen production by nearly 7-fold, and the optimal 5% MoS2 loading further improved the performance by 60%. CM5C3, achieved an apparent quantum efficiency of 7.34%, a 26-fold increase compared to pure CdS. FESEM and HRTEM imaging confirmed the nanorod-like growth of CdS–MoS2 on the CNT surface, with elemental mapping confirming homogenous dispersion of MoS2 and CNTs. In addition, lattice fringe spacings indicated the presence of cubic and hexagonal CdS growing predominantly along the (111) and (002) planes respectively, in addition to MoS2 distributed throughout the crystal lattice. XRD analysis confirmed the presence of hexagonal and cubic CdS, however, MoS2 phases were not registered perhaps due to the low concentration present in the bulk of the material. XPS survey scans showed the presence of C, Cd, Mo, and S only, with trace oxygen impurities. Peak deconvolution indicated the presence of characteristic peaks for CdS and MoS2, in addition to evidence of the presence of Cd–C bonds, indicating strong CdS heterojunctions to the CNT surface.