Thermolysis Route for Accessing Amorphous Metal Sulfide Thin-Film Catalysts for the Hydrogen Evolution Reaction

Abstract

In this work, low temperature thermolysis of metal ethyl xanthates (M = Mo, Co, Fe, Ni) was used to prepare amorphous metal and mixed metal sulfide films on fluorine-doped tin oxide for the hydrogen evolution reaction (HER). Films prepared by dip-coating showed optimal coverage, as monitored by scanning electron microscopy, using high precursor solution concentrations and slow/fast dip-coating retraction rates with low/high volatility solvents. X-ray diffraction confirmed that the films are amorphous. Direct preparation of the active form of amorphous molybdenum disulfide (a-MoS2), proven by x-ray photoelectron spectroscopy, was done, exhibiting electrochemical activity consonant with activated a-MoS2 in the literature. The addition of cobalt and iron to a-MoS2 at an optimal composition of 3:1 Mo:M showed a slight enhancement to current densities. Amorphous iron and cobalt showed activity toward the HER. X-ray photoelectron spectroscopy confirmed the presence of metal sulfide and metal oxide species or homogeneous metal oxysulfide species.