Improving hydrogen evolution reaction and capacitive properties on CoS/MoS₂ decorated carbon fibers

We report a facile method to transform abundantly dumped banana stem fibers into carbon fibers (CFs) useful for energy applications. The CFs surface area is increased by varying the quantity of KOH activation to 488 m²g^-1. The solvothermal method is used to synthesize CoS, CoS/MoS₂ and also grown on the activated carbon fibers (ACFs). Nano nodules of CoS arranged into sheets and layers of MoS₂ stacked together were found in FESEM analysis. The morphology of the CoS/MoS₂ differs when grown on ACFs. The growth of CoS/MoS₂ along the ACFs length prevents any stacking of the pseudocapacitance materials. The ternary composite ACFs/CoS/MoS₂ exhibits superior supercapacitor behavior as well as hydrogen evolution reaction (HER) due to the synergetic effect of the conducting ACF surface and redox active CoS/MoS₂. A maximum specific capacitance of 733 Fg^-1, energy and power density of 33 WhKg⁻¹ and 999 WKg^-1 respectively are obtained. A low Tafel slope value of 61 mVdec⁻¹ is obtained for the ACFs/CoS/MoS₂ ternary composite electrode. The present work therefore offers a fresh insight into the effective conversion of waste materials into electrode material for energy storage and conversion applications.