Low-Temperature Solvothermal Growth of Co_xS_y Nanospheres on Conducting Substrates as Efficient Electrodes for Hydrogen Evolution Reaction

Electrochemical water splitting is widely regarded as a sustainable method for green hydrogen production. An energy-efficient and cost-effective production of hydrogen through hydrogen evolution reaction (HER) requires highly active and low-cost alternatives to the traditional noble metal-based catalysts such as platinum. Hitherto, the search for such alternative electrocatalysts with reliable stability has not been fulfilled. Also, many state-of-the-art synthesis methods are suitable for laboratory conditions, laborious and require expensive synthesis facilities. Here, we have developed a facile low-temperature solvothermal synthesis method for the direct growth of cobalt sulfide-based nanospheres (Co x S y ) on carbon cloth (CC) as binder-free and self-standing working electrodes for direct applications as efficient HER catalysts. Incorporating multiple cobalt precursors during the synthesis is shown to have a positive influence on their HER electrocatalytic performance due to the changes in the particle size distribution and the number density on CC. The as-synthesized electrocatalyst materials (Co x S y /CC) showed good catalytic performance with reliable stability for HER in both acidic (0.5 M H 2 SO 4 ) and alkaline media (1 M KOH), with overpotential values of 143 and 313 mV, respectively, for a current density of 10 mA/cm 2 . The synthesis method followed in this work can be effectively extended to other metal sulfides as well to obtain more efficient HER catalyst materials for future needs.