Ultra-efficient Nitrogen-Doped Carbon Dots-Supported Nickel Sulfide as a Platinum-Free Electrocatalyst for Overall Water Splitting in Basic Medium

The utilization of exceptionally efficient and long-lasting electrocatalysts made from platinum-free materials holds immense promise for mitigating the energy crisis through the production of H2 and O2 via water splitting applications. In this study, a facile hydrothermal method was used to synthesize nitrogen-doped carbon dots (NDCDs) from Luffa acutangula and α-NiS@NDCDs composite from NDCDs, nickel nitrate, and thiourea. The resulting α-NiS@NDCDs composite was characterized using various analytical techniques, such as HR-TEM, EDS, XPS, XRD, and FT-IR. The electrocatalytic hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water splitting reaction (OWS) of NDCDs, α-NiS, and α-NiS@NDCDs composite were evaluated by linear sweep voltammetry, Tafel, chronopotentiometry, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) in 1 M KOH. Remarkably, the α-NiS@NDCDs composite exhibited excellent catalytic activity toward the HER, OER, and OWS, requiring only a low overpotential to achieve a current density of 10 mA cm–2. Furthermore, the greater stability (40 h) of the synthesized α-NiS@NDCDs composite was assessed by chronopotentiometry at a constant current density of 10 mA cm–2. Overall, the synthesized α-NiS@NDCDs composite exhibited promising electrocatalytic activity for the HER, OER, and OWS, highlighting its potential application in energy conversion. The present work confirmed the utility (173 mV, 1.4972 V, and 1.6114 V for the HER, OER, and OWS, respectively) of the α-NiS@NDCDs composite as a promising electrocatalyst for overall water splitting reactions.