Sustainable activated carbon from hemp biowaste: dual heteroatom doping for enhanced supercapacitor performance

Energy consumption is growing exponentially these days, prompting the need for the development of energy storage systems. In this work, the synthesis of N, S-dual-doped activated carbon from hemp cores was developed for high-performance supercapacitors. Conversion of hemp core biomass into N, S-dual-doped activated carbon using thiourea as nitrogen and sulfur sources via activation process was generated. The research focuses on the synthesis factors of activated carbon by comparing thiourea doping levels of 10%wt and 20%wt, as well as activation temperatures. Results indicate that supercapacitor performance is influenced by several factors, including surface area and N and S content. Specifically, at 800°C, thiourea doping increased the specific surface area by 1.2 times, while extreme conditions led to a lack of N and S, resulting in poor performance (175 F g-1). Conversely, at 700°C, thiourea doping improved the specific surface area by 1.46 times and incorporated N and S into the structure, yielding a specific capacitance of 510 F g-1 for the 10%wt thiourea-doped carbon (AC700-2). Utilizing pyroligneous acid from hemp charcoal production as an electrolyte further enhanced performance, achieving a specific capacitance of 672 F g-1—1.32 times higher than the control electrolyte. The highest energy density recorded was 106 Wh kg-1 at a power density of 999.9 W kg-1 in a supercapacitor using N, S activated carbon in a 3M KOH/PA electrolyte. The evaluation of the electrochemical performance indicates that activated carbon and electrolyte generated from hemp cores could potentially be used as a promising electrode material and electrolyte in an electrochemical energy storage supercapacitor. This study indicates that the doping of nitrogen and sulfur into activated carbon exhibited enhanced surface area, porosity, and electrochemical performance.