原位Raman光谱揭示中性条件下硫化钼结构变化对其电催化析氢反应的促进作用

硫化钼是析氢反应(HER)有前途的电催化剂. S-或Mo物种均被认为是形成吸附氢触发HER反应的活性位, 但Mo中心和S配体间相互作用的本质仍不清楚. 另外, 采用中性的水作为质子源用于产氢, 来开发低成本的水裂解催化剂体系为研究者高度关注, 但人们很少研究中性水条件下HER反应的机理. 本文采用原位电化学Raman光谱对所合成的硫化钼中Mo-Mo和S-S物种在中性条件下的结构变化进行了监测. 结果显示, 归属于端位S-S物种的谱带随着Mo-Mo, Mo3-μ3S和Mo-S振动谱带频率而同步变化, 表明Mo-Mo键与端位S-S键起着协同作用, 从而有利于氢气的生成. 这可能是通过三核Mo3-μ3S物种的内部重组而确认的. 本文所揭示的HER反应中金属-配体相互作用的本质与作用表明了一个不同的反应机理, 而以往的机理认为, S或Mo活性位独立起作用而促进HER反应的进行.

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

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 H2evolution 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 molyb-denum 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 demon-strated a mechanism that is distinct from those reported previously in which the S or Mo sites func-tion independently.