Highly Crystallized Cubic Cattierite CoS2 for Electrochemically Hydrogen Evolution over Wide pH Range from 0 to 14

Highly-crystallized cubic cattierite CoS2 pyramids were deposited on Ti foil via a simple hydrothermal method using CoCl2 and thiourea as precursors. Scanning electron microscopy (SEM) characterization revealed the morphology evolution from ramdom nanoparticles to micro-pyramids with well defined facets. These CoS2 pyramids were applied as electrocatalysts for hydorgen evolution reaction (HER) and showed very different acidic HER performance. The sample prepared at 15 h reaction time showed the best performance with an onset overpotential as low as 81 mV and a Tafel slope of ∼72 mV/dec. The activity was kept almost 89% even after working for 30,000 seconds. Further study showed that these CoS2 pyramids also functioned well in neutral (1.0 M potassium phosphate buffer solution, pH = 7.00) and alkaline (1.0 M KOH solution, pH = 13.57) conditions. The cubic cattierite-type CoS2 can work as a novel HER electrocatalyst over the wide pH range from 0 to 14, combined with its easy-synthesis, low-cost and high stability, which can potentially serve as a ready-to-go HER catalyst for practical utilization.