New insights into the formation of amorphous molybdenum sulfide from a tetrathiomolybdate precursor

Abstract

Amorphous molybdenum sulfide (MoS_x) is an attractive Pt-free catalyst for the hydrogen evolution reaction (HER) in both neutral and acidic pH electrolytes. Among the available approaches for the preparation of MoS_x, the electrochemical oxidation and reduction of a tetrathiomolybdate salt ([MoS₄]^2-) represents the most convenient. Herein we describe new insights onto the electrochemical oxidation of [MoS₄]^2- to grow MoSx thin films by employing an advanced technique called electrochemical quartz crystal microbalance (EQCM). These new findings enrich the current understanding of the structure, growth mechanism, redox property and catalytic operation of the MoS_x material.