Chitosan-derived carbon dots/polyaniline-NiS₂ nanostructure for electrochemical water splitting

Currently, the global shift towards sustainable hydrogen generation has spurred efforts to develop advanced and active electrocatalysts for water splitting. However, the high cost and scarcity of platinum and iridium-based materials, which have superior catalytic activity for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively, restrict their widespread application. Here, a systematic doping-dependent nickel disulfide (NiS₂) based nanostructure synthesized through co-precipitation approach to serve as efficient electrocatalyst in alkaline media. Various concentrations 1 and 3 wt percentage (wt.%) of carbon dots (CDs) and a fixed amount (2 wt%) of polyaniline (PANI) were introduced into NiS₂ to form a ternary electrode system. The optimum amount 3 wt% of CDs/PANI-NiS₂ demonstrated the highest electrocatalytic efficiency. The electrochemical characterization revealed that 3 wt% CDs/PANI-NiS₂ achieved an overpotential of ∼201 mV at a current density of 10 mA cm⁻² for OER with low Tafel slope of 44 mV dec⁻¹, and ∼115 mV for HER with a Tafel slope of 172 mV dec⁻¹. These synergistic results encourage that the optimized concentration of CDs in binary system of fixed amount (PANI-NiS₂), fabricated on Ni-foam showed potential as a promising material for electrochemical water splitting.