Abstract
Novel lithium-free gel metal fatty acid (M:FA, M = Co, Cu, and Fe) electrolytes were prepared for use in photosupercapacitor (PSC) applications. Cyclic voltammetry (CV) analysis revealed that the device using the Fe:FA gel electrolyte had a superior specific capacitance (C (p)) of 644 Fg(-1) at 1 mVs(-1). However, for higher scan rates, the Cu:FA gel electrolyte-based PSC performed better compared to the other M:FA. Galvanostatic charge-discharge (GCD) experiments also provided values close to the moderate scan rates of CV experiments, with C (p) values obtained from GCD measurements under 20 Ag(-1) and illumination conditions being 318, 265, and 252 Fg(-1) for Cu, Co, and Fe:FA, respectively. Besides, to assess cyclic stability, devices were tested at a voltage of 1 V and a current density of 60 Ag(-1) for 10,000 cycles. The C (p) retention was found to be 67%, 117%, and 55% of the original capacitance for Cu, Co, and Fe:FA PSCs, respectively, with almost 100% Coulombic efficiency for all PSCs. In line with all of these results, it was concluded that Cu and Fe:FA-based PSC devices combine high performance and durability with low cost and abundance in nature as an alternative to lithium-based electrolytes and shed light on future studies.