In situ study of graphene oxide quantum dot-MoSx nanohybrids as hydrogen evolution catalysts

Abstract

Graphene quantum dots (GOQDs)-MoS_x nanohybrids with different MoS_x stoichiometries (x = 2 and 3) were prepared in order to investigate their chemical stability under hydrogen evolution reaction (HER) conditions. Combined photoemission/electrochemical (XPS/EC) measurements and operando X-ray absorption spectroscopy (XAS) were employed to determine the chemical changes induced on the MoSx-based materials as a function of the applied potential. This in situ characterization indicates that both MoS₂ and MoS₃ materials are stable under operating conditions, although sulphur terminal sites in the MoS₃ nanoparticles are converted from S-dimer (S2^2-) to S-monomer (S^2-), which constitute the first sites where the hydrogen atoms are adsorbed for their subsequent evolution. In order to complete the characterization of the GOQDs-MoS_x nanohybrids, the composition and particle size were determined by X-ray photoemission spectroscopy (XPS), X-ray diffraction (XRD) and Raman spectroscopy; whereas the HER activity was studied by conventional electrochemical techniques.

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ORCID for Andrea E. Russell: orcid.org/0000-0002-8382-6443

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