Accelerated Water Dissociation Kinetics By Electron‐Enriched Cobalt Sites for Efficient Alkaline Hydrogen Evolution

Abstract Sluggish water dissociation kinetics in the Volmer step on platinum‐free electrocatalysts limits the development of hydrogen evolution from economical water‐alkali electrolyser. Herein, an unusual nanosheets electrocatalyst of molybdenum‐doped cobalt selenide with selenium vacancy encapsulated within N‐doped carbon matrix (Mo‐Co 0.85 Se VSe /NC) for efficient hydrogen evolution reaction (HER) is reported. Benefiting from the optimized electronic structure, this Mo‐Co 0.85 Se VSe /NC nanosheet exhibits a high catalytic activity for alkaline HER, achieving the current densities of 10 and 200 mA cm −2 at low overpotentials of 151 and 275 mV, respectively. These results are among the highest catalytic activities in respect with all previously reported transition‐metal‐selenide based HER electrocatalysts. The combined in situ spectroscopic and theoretical studies reveal that the incorporation of Mo‐dopant and Se vacancies into Co 0.85 Se efficiently enhances electron transfer from Mo to Co atom through the bridging Se atom, leading to the formation of enriched electronic Co site to accelerate water dissociation, eventually facilitating the overall alkaline HER process. An integrated Zn‐H 2 O battery with a Mo‐Co 0.85 Se VSe /NC cathode is developed to further demonstrate the potential applications of the newly developed HER catalyst.