Substrate-induced optimization of the electrocatalytic hydrogen evolution reaction (HER) performance of MoS 2 thin films

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Molybdenum disulfide (MoS 2 ) has emerged as a promising, cost-effective catalyst for hydrogen production via water splitting. We investigate the structural and electrocatalytic properties of MoS 2 thin films deposited on different substrates (sapphire(c-Al 2 O 3 ), silicon carbide (SiC), SrTiO 3 (STO)) to study their hydrogen evolution reaction (HER) activity. In particular, in order to study the substrate influence on the stabilization of different polymorphic MoS 2 phases, the films are synthesized using pulsed laser deposition on substrates with different crystal symmetries and lattice parameters. All the deposited samples are characterized by x-ray diffraction, Raman spectroscopy, linear sweep voltammetry, and electrochemical impedance spectroscopy analyses. The films grown on Al 2 O 3 substrates exhibit the best HER performance. Raman spectroscopy reveals the strongest signatures associated with the metastable 1T phase for these samples. Taken together, these observations suggest that the interfacial interactions between film and substrate influence the local polymorphic structure of the MoS 2 films. The enhanced 1T related Raman response observed in the samples grown on Al 2 O 3 correlates with improved charge transfer efficiency and a larger electrochemically active surface area, resulting in enhanced catalytic performance towards the HER.