Electrodeposition of Ni-Co-S Electrocatalyst Using 2,5-dimercapto-1,3,4-thiadiazole as S Precursor for Hydrogen Evolution Reaction at Neutral pH

Among various chalcogenide materials, transition metal sulfides are known to be effective catalysts for the electrochemical hydrogen evolution reaction (HER). In particular, Ni-Co-S is a promising material for the next generation of non-precious metal HER catalysts due to its excellent HER activity in neutral pH solutions. Ni-Co-S is also advantageous in large-scale applications, as it enables relatively simple catalytic synthesis through electrodeposition. In this study, we employed a new S precursor, 2,5-dimercapto-1,3,4-thiadiazole (DMTD), for the electrodeposition of Ni-Co-S, instead of the conventional S precursor, thiourea (TU). Ni-Co-S synthesized with DMTD (Ni-Co-S_DMTD) showed enhanced HER activity at neutral pH compared to that synthesized with TU (Ni-Co-S_TU). It has been found that this improvement in activity is due to the large surface area and high S content of Ni-Co-S_DMTD. The S content and HER activity of Ni-Co-S_DMTD depend on the concentration of DMTD. At the optimal DMTD concentration (12 mM), Ni-Co-S_DMTD exhibited an overpotential of 303 mV at a current density of 10 mA cm^− 2 and a Tafel slope of 99 mV dec^− 1 in a phosphate buffer solution (pH 7.4).

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