N/S-RCQD@NiCo2S4 nanocomposite with wrinkled nanosheet-like edges as an anode for water splitting

The hybrid of carbon quantum dot nanoparticles wrapped at NiCo₂S₄ flower-like with nanosheets-like edges is introduced as a desirable nonprecious electrocatalyst for the oxygen evolution reaction, OER, in the alkaline medium. Co (CH₃COO)₂, Ni(CH₃COO)₂, thiourea, and carbon quantum dots are used as precursors, with ethylene glycol as a dispersant. Reduced carbon quantum dots (RCQD) are doped with sulfur and nitrogen traces. The core-shell structure increases the contact area between the material and the electrolyte, resulting in higher electrochemical performance. Doping of N/S-RCQD to NiCo₂S₄ results in improved electrocatalytic performance and stability. The N/S-RCQD@NiCo₂S₄ only requires a low overpotential of 390 mV for OER at 10 mA.cm⁻², owing to many exposed active sites and facilitated diffusion. Furthermore, in 0.1 M KOH for the OER, the N/S-RCQD@NiCo₂S₄ exhibits outstanding long-term durability. The structure and morphology of N/S-RCQD@NiCo₂S₄ are studied by field emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier Transform Infrared spectroscopy, UV–Vis absorption and photoluminescence excitation and photoluminescence emission. The core-shell structure facilitates molecular diffusion and adsorption of species. The synergistic effect of Ni and Co also enhances the catalytic properties.