Molybdenum/selenium based heterostructure catalyst for efficient hydrogen evolution: Effects of ionic dissolution and repolymerization on catalytic performance.

Transition metal chalcogenides (TMCs) are recognized as highly efficient electrocatalysts and have wide applications in the field of hydrogen production by electrolysis of water, but the real catalytic substances and catalytic processes of these catalysts are not clear. The species evolution of Mo and Se during alkaline hydrogen evolution was investigated by constructing MoSe@CoSe heterostructure. The real-time evolution of Mo and Se in MoSe@CoSe was monitored using in situ Raman spectroscopy to determine the origin of the activity. Mo and Se in MoSe@CoSe were dissolved in the form of MoO and SeO, respectively, and subsequently re-adsorbed and polymerized on the electrode surface to form new species MoO and SeO. Theoretical calculations show that adsorption of MoO and SeO can significantly enhance the HER catalytic activity of Co(OH). The addition of additional MoO and SeO to the electrolyte with Co(OH) electrodes both enhances its HER activity and promotes its durability. This study helps to deepen our insight into mechanisms involved in the structural changes of catalyst surfaces and offers a logical basis for revealing the mechanism of the influence of species evolution on catalytic performance.