CoSe₂ nanosheets decorated on carbon fibers as efficient and stable catalysts for hydrogen evolution reaction

In this study, a novel structure of two-dimensional cobalt selenide (CoSe₂) nanosheets integrating on three-dimensional carbon fibers (CF) have been successfully synthesized by using a facile method. The CoSe₂ has been characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) patterns. The SEM images of the CoSe₂ exhibit sheet-like morphologies densely and uniformly grew on the entire surface of the CF and the XRD result reveals the as-prepared CoSe₂ are pure and crystalline characteristics of orthorhombic phase. Such morphological features may not only provide large surface area for exposing more active sites, but also benefit deep electrolyte penetration for electrons and electrolyte ions. Electrochemical experiments demonstrate the as-prepared CoSe₂ nanosheets-CF possesses 10 mA/cm² at HER overpotential of 0.118 V, as well as a Tafel slope of 53.2 mV/dec (in 0.5 M H₂SO₄). Photoelectrochemical measurements indicate that the current density of CoSe₂ nanosheets significantly increased under light irradiation. The present work provides an attractive non-noble-metal electrocatalyst for highly efficient production of H₂ toward water splitting.