Alteration of cobalt oxalate by ascorbic acid for Faradaic electrode of supercapattery

In this study, we demonstrated the influence of cobalt oxalate hydrate (CoC₂O₄.nH₂O), the working electrode for supercapattery. A binder-free electrode composed of CoC₂O₄.nH₂O synthesized directly on the nickel foam via hydrothermal method. L-ascorbic acid (LAA) was used as a morphology-directing green-reducing agent and as an oxalate source. The structural characterization was rationalized by studying the effect of reaction time on the growth of CoC₂O₄.nH₂O. The electrodes prepared using 8, 10, 12, and 14 drops of potassium hydroxide (KOH) were heated for 6 h. The optimized sample was then selected and heated for 24 h. The crystallinity of the electrode increased with increasing hydrothermal reaction time. In electrochemical measurements, the effects of heating time and different drops of KOH on the formation of different cobalt oxalate hydrates were discussed in detail. The electrode prepared using 10 drops of KOH followed by 6 h of heating process exhibited excellent specific capacity/capacitance even at 10 A g⁻¹ (575 C g⁻¹/1203.64 F g⁻¹) with maximum energy density and power density of 59 Wh kg⁻¹ and 2389 W kg⁻¹, respectively. The supercapattery using CoC (10) exhibited splendid capacity retention of 102% over 10,000 cycles confirming its suitability as a battery-type electrode for supercapattery.