Enhanced performance of activated carbon-based supercapacitor derived from waste soybean oil with coffee ground additives

Abstract

Waste edible oil is discarded in enormous amounts worldwide and poses a serious threat to the environment. The work presented in this paper focuses on the synthesis and fabrication of an electrochemical electrode using waste soybean oil and waste coffee ground to provide enhanced supercapacitive characteristics. We demonstrate a novel method of synthesizing activated carbon (AC) using soot collection, wherein two distinct approaches of mixing coffee ground to waste soybean oil via ultrasonication and hydrothermal treatment have been presented. The two methods lead to different and unique properties in terms of the material porosity, particle size, surface area, carbon and nitrogen content, and the hybridization states of the materials. These properties are correlated with the performance of different supercapacitors. A twofold increase in the highest specific capacitance is observed for the sample prepared using ultrasonication mixing of coffee ground (70.97 Fg-1 at 0.5 mA cm−2) compared to the sample prepared using hydrothermal technique (36.79 Fg-1 at 0.5 mA cm−2). The ultrasonicated sample has a surface area of 684.71 m2g-1. A capacitance retention of ∼90% is observed after 1010 cycles showing good device stability.