The hydrogen evolution reaction (HER) under alkaline conditions is subject to significant kinetic limitations even with the most active platinum-based catalysts, while more affordable non-noble-metal-based catalytic materials present further challenges in terms of activity and durability in operation. To improve on these aspects, we present a new microwave-assisted synthetic route to fabricate sulfides of nickel and cobalt integrated into a layer expanded molybdenum sulfide (NiS x /MoS 2 LE and CoS x /MoS 2 LE ), which efficiently catalyze H 2 evolution in 1 M KOH. The use of the microwave-synthesis conditions enables the formation of nanoscale Ni and Co sulfides distributed homogeneously within the highly disordered layered molybdenum sulfide, as established using a comprehensive suite of physical methods. Synthesis of FeS x /MoS 2 LE is also presented, but the resulting material did not exhibit promising properties. Electrocatalytic tests reveal higher activity of the Ni-based catalyst as compared to CoS x /MoS 2 LE and especially unmodified MoS 2 LE . The performance of NiS x / MoS 2 LE at a HER overpotential of 0.15 V at ambient temperature and 60 °C corresponds to specific H 2 evolution rates of 28 ± 4 and 58 ± 10 A g −1 , respectively. Analysis of the electrokinetic data indicates that the exchange current density of the HER per an electrochemically active surface area of the sulfide-based materials is not high (∼0.001 mA cm −2 at ambient temperature), and that the high performance per unit mass observed here is supported by the well-developed surface area of the material (corresponding to a specific capacitance of ∼71 F g −1 ). A similar conclusion likely applies to many nickel and cobalt sulfide-based alkaline hydrogen evolution catalysts reported previously. Durability in operation of NiS x /MoS 2 LE and CoS x /MoS 2 LE is also demonstrated, in particular through a 2-week-long two-electrode water splitting test.
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