Electrochemical Performance of NiCo 2 O 4 Thin Films Over Stainless Steel Synthesized by Chemical Bath Deposition

NiCo 2 O 4 thin films were fabricated on SS‐304 substrates using a cost‐effective CBD method by varying the deposition time (3, 4, and 5 h) to regulate the thickness and porosity. XRD confirmed the formation of phase‐pure polycrystalline spinel NiCo 2 O 4 with no detectable secondary phases, with only minor structural variations observed with deposition time. SEM analysis revealed interconnected porous nanograin networks, whereas the porosity gradually decreased with the deposition time. AFM studies also indicated that the surface roughness decreased with deposition time, offering more electrochemically active sites in the NCO 1 sample. Electrochemical measurements in a 2 M KOH electrolyte demonstrated clear pseudocapacitive behavior with distinct redox peaks. NCO 1 exhibited the highest specific capacitance of 312.18 F g −1 at 5 mV s −1 , followed by NCO 2 (264.75 F g −1 ) and NCO 3 (134.15 F g −1 ). The GCD results also supported this trend, and the EIS analysis showed the lowest charge‐transfer resistance for NCO 1 , indicating faster redox kinetics and better ion diffusion. The NCO 1 electrode demonstrated the highest GCD‐derived specific capacitance, achieving an impressive 780 F g −1 at a current density of 1 A g −1 . Overall, this study suggests that the optimized deposition time critically governs the electrochemical performance.