Active-defective activated carbon/MoS₂ composites for supercapacitor and hydrogen evolution reactions

Low-cost, earth-abundant, clean and high stability material are of undivided interest for energy storage and conversion. The present work involves the investigation of one such material, activated carbon (AC), that is derived from abundantly available biomass – Tendu leaves. The work also addresses hydrothermal synthesis of 2-D MoS₂ layers and composites with AC, for supercapacitors and hydrogen evolution reaction (HER). AC derived from Tendu leaves showed micro and mesopore structure with high specific surface area (SSA) of 1509 m² g⁻¹. Layered MoS₂ nanosheets sheets, showed a biphasic system namely, 1-T and 2-H. Different ratios of AC and MoS₂ nanocomposites are prepared. And the best ratio composites tested for symmetric and hybrid supercapacitor electrodes and HER. Symmetric supercapacitor and hybrid supercapacitors exhibited good cycle stability and show higher specific capacitance of 261 F g⁻¹ and 193 F g⁻¹ respectively, at a scan rate of 2 mV s⁻¹. Defective sites were created on AC for electrochemical HER. The defects were created through, hydrothermal N doping followed by high-temperature dedoping of the N-doped AC. The defective activated carbon (DAC) showed a reduction in SSA of 1300 m² g⁻¹. The nanocomposites of DAC/MoS₂ were then tested for HER. The nanocomposites exhibited enhanced catalytic activity owing to better hydrogen evolution with lesser Tafel slope of −84 mVdec⁻¹.