Response surface optimization of polypyrrole-modified biochar electrodes for enhanced capacitive performance

Developing low-cost and high-performance carbon-based electrodes is essential for efficient renewable energy storage. Polypyrrole-modified biochar (Ppy-BC) was prepared from corn stalks via in-situ oxidative polymerization, and the preparation conditions were optimized using a Box-Behnken design and response surface analysis. Pyrrole concentration, ferric chloride concentration, and modification time were selected as variables. Under the optimal conditions(0.4 mol·L⁻¹ pyrrole, 2 mol·L⁻¹ FeCl₃, 4 h), Ppy-BC achieved a specific surface area of 468.2 m²·g⁻¹ and a specific capacitance of 345 F·g⁻¹ at 0.5 A·g⁻¹, with 91.12% retention after 5000 cycles at 10 A·g⁻¹. The response surface model further confirms a strong correlation between pore structure and electrochemical performance. Polypyrrole modification significantly enhances the conductivity and energy storage capacity of biochar, showing great potential for agricultural waste utilization and high-performance supercapacitor electrodes.