Evaluation of alkaline reagent mediated synthesis of Co₃O₄ thin films on the morphology and electrochemical performance for supercapacitor applications

This study presents a comparative analysis of cobalt oxide (Co₃O₄) thin films synthesized via electrodeposition using two different alkaline reagents—ammonium hydroxide (NH₄OH) and sodium hydroxide (NaOH)—on stainless steel substrates. The film prepared with NH₄OH exhibited enhanced crystallinity, confirmed by sharper (311) XRD peaks, and a highly porous morphology favourable for charge transport. FTIR and XPS characterizations confirmed the successful formation of spinel Co₃O₄ and the appropriate oxidation states of cobalt. Electrochemical evaluation in 1 M KOH showed that the electrode synthesized using NH₄OH delivered a specific capacitance of 1323 F/g at 10 mV/s, while maintaining 95.74% of its capacitance after 2000 charge–discharge cycles. These findings highlight that the type of alkaline reagent plays a crucial role in tailoring the structural and electrochemical behaviour of Co₃O₄ thin films, offering a viable route to optimize electrodes for enhanced energy storage supercapacitor applications.