Direct Evidence of the Role of Co or Pt, Co Single-Atom Promoters on the Performance of MoS2 Nanoclusters for the Hydrogen Evolution Reaction

Developing alternatives to platinum (Pt) and iridium (Ir) in proton-exchange membrane water electrolyzers is crucial on the way to viable energy provision schemes. However, although it seems difficult to substitute Ir, alternatives exist for Pt at the proton-exchange membrane water electrolyzer cathode. Here, we report on the synthesis and the characterization of efficient and durable hydrogen evolution reaction (HER) nanocatalysts based on MoS2 supported on high-surface-area carbon. Citric acid was used as a chelating agent to control the size of the MoS2 crystallites (1.4 nm) and thus the density of active sites (slab edges). Inspired by successful approaches in catalysis for hydrodesulfurization reactions, conventional 2H MoS2 was sequentially doped with cobalt (Co) and then with 1 wt % of Pt. Overpotentials of 188, 140, and 118 mV at 10 mA cm-2 are reported for MoS2/C, Co- MoS2/C, and Pt1%-CoMoS2/C, respectively. This result is attributed to the weakening of the Hads binding energy of the promoted MoS2-edge active sites (because the promoting atoms are mostly located at the edges). Associated with small-metal dissolution rates (monitored in situ, during the HER), our findings demonstrate that metal promotion (doping) is a promising route to replace Pt with earth-abundant elements in acidic water electrolyzers.