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

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 (ΔG_H*) 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.