FU Shihui^a ，LI Yuan^a ，WANG Yanqing^a，b

a. College of Polymer Science and Engineering，b. State Key Laboratory of Polymer Materials Engineering，

Sichuan University， Chengdu 610065， China

Objective Hybrid supercapacitors can achieve higher energy densities without compromising the device’s output power and cycle life. To develop hybrid supercapacitors with excellent energy storage performance and advance renewable， clean energy storage technologies， porous carbon is used as the electrode material. Porous carbon has a high specific surface area and specific capacitance， along with good physicochemical stability. However， issues like nanoplate aggregation and stacking result in low charge storage efficiency. Therefore， introducing foreign atoms into the carbon framework can alleviate the stacking phenomenon through the electrostatic repulsion of functional groups， while the heteroatoms provide more electrochemically active sites， enhancing charge storage capability. Doping porous carbon with elements like boron （B） and nitrogen （N） increases defects in the carbon structure， improving its electrochemical energy storage performance.

Methods Ethylenediaminetetraacetic acid （EDTA） tetrasodium salt was used as the carbon source， while ammonium borate，sodium borate， and ammonium chloride were used as the B and N doping sources. The mixture was thoroughly stirred to obtain a solution， which was then subjected to repeated freezing and drying to produce the precursor. The precursor was calcined in a tube furnace under a nitrogen atmosphere at temperatures of 600 ℃，700 ℃， and 800 ℃ with a heating rate of 5 ℃/min. After cooling， the samples were purified and filtered. The resulting B-N co-doped porous carbon （B-N-porous carbon）， undoped porous carbon， and single-element doped porous carbon （B-porous carbon， N-porous carbon） samples were dried and ground.To study the specific capacitance， power density， and cycling stability of the porous carbon electrode materials， the samples were characterized and tested. Scanning electron microscope （SEM） and transmission electron microscope （TEM） were used to analyze the microstructure， energy dispersive spectrometer （EDS） for elemental composition， and Raman， X-ray diffraction（XRD）， and X-ray photoelectron spectroscope （XPS） spectra for structural and compositional analysis. Brunauer-EmmettTeller （BET） analysis was used to determine the specific surface area and pore size of the porous carbon. Electrochemical performance was tested using galvanostatic charge-discharge （GCD）， cyclic voltammetry （CV）， electrochemical impedance spectroscopy （EIS）， and long-term cycling tests.

Results and Discussion B-N-porous carbon exhibited a highly disordered nanoporous amorphous structure， with micropores，mesopores， and macropores， a specific surface area of 668 m²/g， and a total pore volume of 0. 9 cm³/g. The distribution of N，B， C， and O elements was uniform， with mass fractions of N and B being 13. 12% and 3. 24%， respectively. B-N-porous carbon had a low degree of graphitization， a high degree of disorder， a large number of defects， strong ion adsorption capacity，and the best charge-discharge performance. At the same current density， B-N-porous carbon had the highest specific capacity and capacity retention rate. It exhibited the lowest charge transfer resistance， enabling rapid electron conduction and ion transport. B-N-porous carbon also demonstrated the best cycling stability and pseudocapacitive behavior， with its specific capacity remaining stable after more than 500 cycles.

Conclusion When the amount of ammonium borate addition is 20 mmol， and the calcination temperature of preparing for B-N-porous carbon is 700 ℃， the B-N-porous carbon exhibits the best microstructure and electrochemical performance. The B-N co-doping and calcination method successfully produces porous carbon electrode materials with excellent performance，providing a foundation for hybrid supercapacitor components.

Keywords：boron-nitrogen co-doping； porous carbon； electrode material； supercapacitor； energy storage performance