Metal-organic framework (MOF)-derived plate-shaped CoS nanoparticles for an improved hydrogen evolution reaction.

Metal-organic framework (MOF)-derived transition metal sulfides are viewed as reliable, cost-effective, and alternative hydrogen evolution reaction (HER)-efficient electrocatalysts. They have been used to replace platinum (and their alloys) for production of renewable energy carriers such as hydrogen. Progress towards development of non-precious transition-metal sulfides through different synthetic routes to obtain unique morphological nanostructures with enhanced HER activity is challenging. We introduced a transition-metal sulfide, cobalt sulfide (CoS), derived from a cobalt MOF [Co-BPY-DDE] by following facile, one-step solvothermal sulfurization. By varying the sulfurization temperature (from 140 °C to 180 °C) during the solvothermal method, three cobalt-sulfide products were obtained: CoS-140, CoS-160, and CoS-180, respectively. Temperature variation had a vital role in optimizing the HER activity of the electrocatalyst. Besides, notable plate-shaped cobalt sulfide nanoparticles (CoS-160) required overpotential of 163 mV to deliver a current density of 10 mA cm with a low Tafel slope of 53 mV dec, thereby demonstrating faster reaction kinetics during the evolution of molecular hydrogen. Furthermore, 25 h of long-term stability of the electrocatalyst reflected its practical applicability in acidic media. CoS-160 had uniform plate-shaped morphology and large electrochemical active surface area, which contributed to enhanced electrochemical performance through water electrolysis.