Multifunctional carbon-armored Ni electrocatalyst for hydrogen evolution under high current density in alkaline electrolyte solution

Hydrogen evolution reaction (HER) electrocatalysts capable of long-term operation under high current densities are key to the industrialization of water-splitting technology. Although numerous efforts have been devoted to expose active sites sufficiently while increasing the intrinsic catalytic activity, effects of non-kinetic factors on catalytic efficiency have not yet been comprehensively investigated. Herein, multifunctional carbon-armored nickel nanoparticles (NC@NiNPs) were fabricated using an in-situ polymer encapsulation method for use as a HER electocatalyst. NC@NiNPs exhibited low overpotential (74 mV at 10 mA cm -2 ), low Tafel slope (85.49 mV dec -1 ) and excellent stability (over 260 h at 1400 mA cm -2 ). Surprisingly, although the intrinsic activity of NC@NiNPs was lower than that of commercial 20 % Pt/C, NC@NiNPs provided markedly greater current density than 20 % Pt/C as the operating voltage was increased. This result implied that non-kinetic factors influenced the HER process, prompting this investigation to identify these unknown factors.