Hydrogen Evolution on Supported Incomplete Cubane-type [Mo₃S₄]⁴⁺ Electrocatalysts

Abstract

Electrocatalytic properties of biomimetic supported incomplete cubane-type [Mo 3 S 4 ] 4+ clusters are investigated. The activity toward the hydrogen evolution reaction (HER) is evaluated on both a high surface area gas diffusion electrode in a membrane electrode assembly and on highly orientated pyrolytic graphite (HOPG) supports. Sub-monolayers of the clusters were imaged by means of scanning tunnelling microscopy (STM) prior to electrochemical characterization. This enabled the quantification of the activity on a per cluster basis for the HER and the comparison of the activity with other HER catalysts. We find that the HER activity of the [Mo 3 S 4 ] 4+ is comparable with that of the edge sites of MoS 2 . The supported [Mo 3 S 4 ] 4+ molecules were also characterized by X-ray photoelectron spectroscopy (XPS), and the observed deterioration in electrocatalytic activity with time was assigned to slow [Mo 3 S 4 ] 4+ cathodic desorption from the catalyst support.