Boosting Alkaline Hydrogen Evolution Reaction via an Unexpected Dynamic Evolution of Molybdenum and Selenium on MoSe_2 Electrode

摘要

Transition metal chalcogenides are a promising and extremely pivotal classof electrocatalysts with potential applications in alkaline hydrogen evolutionreaction (HER), especially, molybdenum diselenide. Although the exposededge sites are generally considered to be the active sites of MoSe_2 for HER, anintrinsic behavior (surface species evolution, structure/morphology conversion,stability) of MoSe2 electrode itself was not unveiled. Herein, the origin ofMoSe_2-electrocatalyzed HER activity monitored by the quasi-operando XPS andin situ Raman spectroscopy is presented. The findings clearly show dynamicevolution of both Mo and Se species on MoSe2 electrode surface for promotingHER activity and maintaining long-term catalytic stability and reveal an electrooxidativedissolution and re-adsorption mechanism. Theoretical calculationsalso corroborate these results. As expected, the addition of single or mixedMoO_4~(2?) and SeO_3~(2?) to the electrolyte of nickel foam directly verifies the criticalrole of surface-adsorbed Mo and Se species for boosting HER activity andstability. Additionally, the oxidative dissolution of Se on NixSey electrode surfaceduring HER is also observed, revealing the universality of oxidative dissolutionof Se in transition metal selenides. This study provides a unique insight into thespecies evolution and surface structure transformation mechanism and activityimproved origin of materials during the electroreduction process.