Chemical and structural engineering of transition metal boride towards excellent and sustainable hydrogen evolution reaction

Herein, holey, thin, conductive nickel substituted cobalt molybdenum boride (Ni-CMB) nanosheets have been designed to obtain superior electrochemical HER performance with small overpotential of 69 mV at 10 mA cm^-2 current density and lower Tafel slope of 76.3 mV dec^-1 in alkaline medium. Incorporation of Ni leads to improved conductivity and favorable hydrogen adsorption on Mo sites, which collectively yield efficient electrocatalytic H₂ production from Ni-CMB catalyst. The ultrathin nature (thickness = 5.0 nm) of the designed material expectedly helps to attain high exposure of active sites and facile charge transportation through the nanosheets. Additionally, the decorated mesopores (average size = 3.86 nm) on nanosheets have benefitted towards faster electrolyte diffusion, easy gas escape from catalyst surface to support high electrocatalytic performance. Finally, well-maintained morphology of the sample and evolution of HER active sites in the material have guaranteed long-term, sustainable hydrogen production even at high current densities, which clearly demonstrate its superiority over an expensive electrolyzer (Pt-C) in alkaline water.