Ni-WSe₂ as an efficient catalyst for electrochemical hydrogen evolution reaction (HER) in acidic and alkaline media

Similarly to Molybdenum disulfide, tungsten diselenide may prove as a remarkable platform for advanced catalytic applications. Here, we report the synthesis of WSe₂ doped by various transition metals (Fe, Co, Nb, Ni, Zr). Among the doped catalysts, Ni-WSe₂ is the most promising electrocatalyst for electrochemical hydrogen evolution reaction. The controlled synthesis of Ni-doped nanostructures maintained similar morphology with feed ratios of 3%, 5% and 10% Ni, offering an opportunity to study the effect of Ni doping on the catalytic activity. The 10 % Ni-doped WSe₂ exhibits a significantly improved HER performance with over potential at 10 mA cm^-2 of 259 mV in acid with Tafel slope of 86 mV dec^-1 and 215 mV in alkaline with Tafel slope of 109 mV dec^-1_, much better than reported for pristine and doped WSe₂. Moreover, Ni-WSe₂ possesses the smallest charge transfer resistance, which contributes to the facilitated faster catalytic reaction. The analysis shows that upon doping with up to 3% Ni, the catalytic enhancement originates from improved hydrogen adsorption (H_ads). Beyond this threshold of Ni loading, the improved activity in alkaline medium results from optimized interaction of the OH/surface active sites. Using the density functional theory calculations, we identified two possible structures as the catalytic active sites: the Se atoms either bound to a substitutional Ni dopant or constituting a small patch of NiSe grafted on the WSe₂ surface.