Activated Proton Storage in Molybdenum Selenide through Electronegativity Regulation

Layered transition metal dichalcogenides (TMDs) are promising candidates for aqueous zinc-based batteries owing to the large interlayer distance. Nevertheless, the low specific capacity of unmodified TMDs due to the high binding energy between host materials and carriers in electrolytes hinder their further development. Herein, a simple method to incorporate oxygen is reported to enhance the specific capacity of MoSe2. The in situ and ex situ characterization results confirm that the oxygen incorporated MoSe2 experiences proton-dominated insertion electrochemistry during cycling. In addition, the theoretical calculation results demonstrate that the oxygen atoms with high electronegativity can effectively reduce the binding energy of adsorbing H+ and change charge distribution in the interlayer. As a result, incorporating oxygen significantly promotes H+ adsorption and diffusion, and thus greatly increases the specific capacity of MoSe2. This study provides an effective strategy to facilitate the kinetics of TMDs, and thus achieve high-performance aqueous zinc-based batteries.