Regulating electronic structure and adsorptivity in molybdenum selenide for boosting electrocatalytic water splitting

Abstract Rationally designing highly efficient, cost-effective electrocatalysts towards overall water splitting to substitute noble-metal-based catalysts currently is still an outstanding challenge for renewable energy conversion. Herein, we demonstrate multiscale regulation of MoSe2 by CoSe tailoring for achieving significantly increased activity as a bifunctional electrocatalyst for highly efficient overall water splitting. X-ray absorption near-edge structure (XANES) and ultraviolet photoelectron spectroscopy (UPS) measurements unravel electron transfer from CoSe to MoSe2 as well as the increase of atomic disorder degree and the decrease of coordination number for MoSe2, thus facilitating efficient and fast interfacial charge transport and meanwhile providing more electrocatalytic active sites. Moreover, the introduced CoSe species not only improves the water adsorption/dissociation capability of MoSe2 by providing additional water adsorption sites, which is crucial for subsequent fast H2 generation, but also promotes MoSe2 to realize bifunctional behavior. Besides, density functional theory (DFT) calculations further reveal that CoSe modification for MoSe2 could evidently tailor d-band center of MoSe2 and accordingly significantly reduce hydrogen-adsorption Gibbs free energy (ΔGH*) of MoSe2 from 0.78 to 0.16 eV, along with an enhanced electronic conductivity owing to the increased electronic states near the Fermi level based on density of states (DOSs). This work gives a deeper insight for the relationship between multiscale regulation strategy and intrinsic activity of materials.