Nanoarchitectonics of N- and S-Doped Nanoporous Biocarbons with High Specific Surface Area from Casein and Dithiooxamide for Supercapacitor Applications

Abstract

Porous carbons are ideal contenders for supercapacitor electrodes; however, challenges in creating a high surface area in conjunction with controlled surface functionalization still exist. Herein, a low cost and green route for the synthesis of nitrogen and sulfur codoped nanoporous biocarbons using casein and dithiooxamide with high specific surface areas is reported. The textural properties are tuned by varying the synthesis temperature, wherein the nitrogen-doped porous carbon (N-PC) shows a high surface area (2132 m² g⁻¹) and ample microporosity (>90%). The N and S codoped porous carbons shows considerable surface areas (2068–1944 m² g⁻¹). N-PC displays a specific capacitance of 149 F g⁻¹ at a current density of 0.5 A g⁻¹ in a three-electrode system. Interestingly, N and S codoped material N,S-PC₅₀₀ shows an uplift of ≈20% (178 F g⁻¹) in the specific capacitance. The synergetic effect of S and N heteroatoms enhances the specific capacitance due to the provision of additional electrochemical active sites and enhances conductivity. N,S-PC₅₀₀ also reveals a capacity retention of 93.2% after 3000 cycles at a current density of 5 A g⁻¹. Overall, N and S codoping in porous carbon prove to be a facile ploy to enhance the specific capacitance of materials.