Ball-milled zinc nickel sulfide nanostructures on nickel substrate for enhanced electrochemical methanol sensing.

Zinc-nickel sulfide (ZnNiS) nanostructures were synthesized via a simple ball-milling process followed by low-temperature annealing and investigated exclusively as a surface-modifying layer for electrochemical methanol sensing on conductive substrates. Structural characterization using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning and transmission electron microscopy confirmed the formation of nanocrystals with a mixed orthorhombic-trigonal phase and particle sizes in the range of 50-150 nm. BET analysis revealed a mesoporous morphology with a high specific surface area, while thermal analysis confirmed stability up to 550 °C, supporting their suitability for electrochemical applications. Electrochemical measurements using cyclic voltammetry and linear sweep voltammetry demonstrated that methanol oxidation is primarily driven by the nickel substrate, with ZnNiS acting as a nanostructured catalytic modifier that enhances active surface sites and facilitates charge transfer processes. The optimized electrode configuration exhibited sensitivities of 62.785 µA mM-1 on Ni-based electrodes and 3.8214 µA mM-1 on stainless steel, confirming the dominant role of the substrate in governing the overall response. Kinetic analysis indicated pseudo-second-order adsorption behavior, consistent with chemisorption-controlled electrooxidation of methanol. Overall, the study highlights the synergistic interaction between ZnNiS nanostructures and the Ni substrate, leading to improved electrochemical sensing performance for cost-effective methanol detection.