Low-temperature synthesis of NiS/MoS2/C nanowires/nanoflakes as electrocatalyst for hydrogen evolution reaction in alkaline medium via calcining/sulfurizing metal-organic frameworks

Based on four precursors of metal-organic frameworks (MOFs) or coordination compounds with different Ni/Mo ratios (1:1, 1:4 or only Mo involved), four electrocatalysts with different NiS/MoS2 molar ratios have been obtained via low temperature calcining and sulfurizing technique. Among the four precursors, MOF 2/AC precursor exhibits a regular morphology of 3D bunched nanorods due to the addition of the hard template of activated carbon (AC) during the synthesis of MOF 2. As a result, the calcined product, S2/AC (NiS/MoS2 = 1:4) exhibits a morphology of the hierarchical nanorods built by MoS2/C nanowires and NiS/MoS2 nanoflakes, and it shows the best hydrogen evolution reaction activity in alkaline electrolyte among the four electrocatalysts with an overpotential of 117 mV at 10 mA cm(-2), a small Tafel slope of 58 mV and excellent electrochemical durability, which was probably attributed to the excellent conductivity, abundant exposed active sites and synergistic effect of the different components in the sample. Moreover, S2/AC exhibited an improved electrocatalytic activity for hydrogen evolution reaction (HER) after stability test with a decreased overpotential (98 mV) at 10 mA cm(-2), which was probably due to the improved morphology of the sample with more dispersed nanowires and nanoflakes after the stability test, leading to more NiS active sites exposed to the electrolyte. The detailed mechanism is under investigation. (C) 2018 Elsevier Ltd. All rights reserved.