Electrodeposited Heterostructures of Cobalt Sulfide/Molybdenum Sulfide Trigger both Acidic and Alkaline HER

Abstract

MoS2 has attracted significant attention as a non-platinum group electrocatalyst for the hydrogen evolution reaction (HER). There have been extensive efforts demonstrating that by doping MoS2 with various transition metals, such as Co, the HER activity of the catalyst is enhanced. In particular, this work has shown that various cobalt sulfide phases can act as a co-catalyst with MoS2. Here, we report on the electrodeposition of a c-CoSx/MoS2 heterostructure catalyst for the HER reaction in both acidic and alkaline conditions. Using Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and scanning electron microscopy, it is demonstrated that depending on the precursor concentrations, various morphologies, grain size, and c-CoSx phases can be achieved, all of which have an impact on the activity and stability of the c-CoSx/MoS2 catalysts. The most promising catalyst composition demonstrated excellent stability in both acidic and alkaline conditions with low overpotentials to reach 10 mA cm−2 of 112 mV and 60 mV and with Tafel slopes of 113 mV dec−1 and 81 mV dec−1, respectively. This report demonstrates that the c-CoSx/MoS2 heterostructure is one of the most catalytically active materials for HER, especially in alkaline conditions.