Novel Cobalt-Doped Ni0.85Se Chalcogenides (CoxNi0.85-xSe) as High Active and Stable Electrocatalysts for Hydrogen Evolution Reaction in Electrolysis Water Splitting

In this paper, novel cobalt-doped Ni0.85Se chalcogenides (CoxNi0.85-xSe, x = 0.05, 0.1, 0.2, 0.3, and 0.4) are successfully synthesized and studied as high active and stable electrocatalysts for hydrogen evolution reaction (HER) in electrolysis water splitting. The morphologies, structures, and composition of these as-prepared catalysts are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and transmission electron microscopy. The electrochemical tests, such as linear sweep voltammetry, cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry testing, are performed to evaluate these catalysts' HER catalytic performance including activity and stability. The results indicate that a suitable doping can result in synergetic effect for increasing the catalytic performance. Among different catalysts, Co0.1Ni0.75Se shows the highest HER performance. After introducing the reduced graphene oxide (rGO) into this catalyst as the support, the resulted Co0.1Ni0.75Se/rGO shows even better performance than unsupported Co0.1Ni0.75, which are confirmed by the reduction of HER overpotential of Co0.1Ni0.75/rGO to 103 mV compared to 153 mV of Co0.1Ni0.75 at a current density of 10 mA/cm(2), and the smaller Tafel slope (43 mV/dec) and kinetic resistance (21.34 Omega) than those of CoosiNioisSe (47 mV/dec, 30.23 Omega). Furthermore, the large electrochemical active surface area and high conductivity of such a Co0.1Ni0.75Se/rGO catalyst, induced by rGO introduction, are confirmed to be responsible for the high HER performance.