Structural change of molybdenum sulfide facilitates the electrocatalytic hydrogen evolution reaction at neutral pH as revealed by in situ Raman spectroscopy

• Published in: Chinese journal of catalysis Vol. 39; no. 3; pp. 401 - 406
• Main Authors: Li, Yamei, Nakamura, Ryuhei
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2018
• Subjects: Artificial photosynthesis; Clean energy; Electrocatalyst; Hydrogen evolution reaction; In-situ Raman spectroscopy; Molybdenum sulfide; Hydrogen evolution reaction; Electrocatalyst; Molybdenum sulfide; Clean energy; In-situ Raman spectroscopy; Artificial photosynthesis
• ISSN: 1872-2067; 1872-2067
• DOI: 10.1016/S1872-2067(17)62945-0

Molybdenum sulfides are promising electrocatalysts for the hydrogen evolution reaction (HER). S- and Mo-related species have been proposed as the active site for forming adsorbed hydrogen to initiate the HER; however, the nature of the interaction between Mo centers and S ligands is unclear. Further, the development of cost-effective water-splitting systems using neutral water as a proton source for H2 evolution is highly desirable, whereas the mechanism of the HER at neutral pH is rarely discussed. Here, the structural change in the Mo−Mo and S−S species in a synthesized molybdenum sulfide was monitored at neutral pH using in situ electrochemical Raman spectroscopy. Analysis of the potential dependent Raman spectra revealed that the band assigned to a terminal S−S species emerged along with synchronized changes in the frequency of the Mo−Mo, Mo3−μ3S, and Mo−S vibrational bands. This indicates that Mo−Mo bonds and terminal S−S ligands play synergistic roles in facilitating hydrogen evolution, likely via the internal reorganization of trinuclear Mo3−thio species. The nature and role of metal-ligand interactions in the HER revealed in this study demonstrated a mechanism that is distinct from those reported previously in which the S or Mo sites function independently. Synergy between trinuclear Mo centers and di-sulfur ligands for facilitating electrocatalytic hydrogen evolution was revealed using in situ Raman spectroscopy at neutral pH, providing important insights into the nature of metal-ligand interactions in the hydrogen evolution.