Hydrogen Evolution at Liquid|Liquid Interfaces Catalysed by 2D Materials

The hydrogen evolution reaction (HER) plays a crucial role in clean energy production in hydrogen fuel cells. In order to utilise this process effectively, new catalysts are required that are cheap, non-toxic and efficient. In this context, 2D materials such as transition metal dichalcogenides (e.g. MoS2) should offer the desired properties but have so far proven difficult to manufacture into useful devices. In this work, liquid|liquid interfaces are used for the assembly and testing of the catalytic efficiency of a number of 2D materials and their composites, exploiting the ability of the materials to self-assemble at these interfaces and be tested electrochemically in situ. MoS2, WS2, and graphene were developed for hydrogen evolution at the water|1,2-dichlorobenzene (DCB) interface. The exfoliation process was carried out in DCB and resulted in multi-layer MoS2, few layer WS2 and graphene: when assembled at the water|DCB interface, these materials acted as efficient HER catalysts. HER was investigated using voltammetry, with bulk reaction kinetics monitored by in-situ UV-visible spectroscopy at a constant potential. MoS2 exhibited the highest performance of the catalysts examined, with an average rate constant of 0.0132 ± 0.063 min-1 at an applied Galvani potential of +0.5 V. This is ascribed to the sulphur edge sites of MoS2, which are known to be active for hydrogen evolution predominantly.