Attaining promising efficiency through a Quasi-Solid-State symmetrical supercapacitor and Dye-Sensitized solar cell counter electrode utilizing bifunctional Nitrogen-Doped microporous activated carbon

This study addresses the imperative need for high-performance and sustainable energy storage and conversion technologies by leveraging the unique properties of nitrogen-doped porous carbon (N@WnAC) derived from the waste walnut shells (WnS). In the realm of supercapacitors, the N@WnAC demonstrates remarkable performance in a three-electrode system, showcasing a high specific capacitance value of 276.7 Fg-- 1 at 1 Ag-1,- 1 , outstanding stability (96.6 %, 5000 charge-discharge cycles) and favourable rate capability (68.8 % at 10 Ag-- 1 ). Moreover, a quasi-solid-state symmetrical supercapacitor (N@WnAC//N@WnAC) is fabricated with PVA/H2SO4 2 SO 4 gel electrolyte, underscores outstanding performance by delivering high capacitance (126.2 Fg-- 1 at 0.5 Ag-- 1 ), promising rate capability (71.8 % at 5 Ag-1),- 1 ), favourable long-term stability (93.3 %, 5000 charge-discharge cycles), and faster charge-discharge kinetics compared to conventional counterparts. At the same time, N@WnAC// N@WnAC delivers a high energy density (42.27 Whkg-- 1 at 0.5 Ag-- 1 ) that was retained up to 23.96 Whkg-- 1 even at 5 Ag-- 1 . Simultaneously, the study explores the potential of N@WnAC as a counter-electrode (CE) in dye- sensitized solar cells (DSSC). The obtained results underscore that unique nitrogen doping enhances the electrocatalytic activity, leading to improved electron transfer kinetics and overall cell performance. Moreover, the N@WnAC CE-based DSSC delivers a promising overall solar-to-electrical conversion efficiency of 5.84 %.