Enhancing the supercapacitive performance of a carbon-based electrode through a balanced strategy for porous structure, graphitization degree and N,B co-doping

Regarding carbon -based electrodes, simultaneously establishing a well-defined meso -porous architecture, introducing abundant hetero-atoms and improving the graphitization degree can effectively enhance their capacitive performance. However, it remains a significant challenge to achieve a good balance between defects and graphitization degree. In this study, the porous structure and composition of carbon materials are co -optimised through a 'dual -function ' strategy. Briefly, K 3 Fe(C 2 O 4 ) 3 and H 3 BO 3 were hybridised with a gelatin aqueous solution to form a homogeneous composite hydrogel, followed by lyophilisation and carbonisation. Owing to the dual functionality of raw materials, the graphitization, activation and hetero-atom doping processes can occur simultaneously during a one-step high -temperature treatment. The resultant carbon material exhibits a high graphitization degree (I D /I G = 0.9 +/- 0.1), high hetero-atom content (N: 9.0 +/- 0.3 at.%, B: 6.9 +/- 0.5 at.%) and a large specific area (1754 +/- 58 m 2 /g). The as -prepared electrode demonstrates a superior capacitance of 383 +/- 1F g - 1 at 1 A/g. Interestingly, the cyclic voltammetry (CV) curves exhibit a distinctive pair of broad redox peaks, which is uncommon in KOH electrolyte. Experiment data and density functional theory (DFT) simulation verify that N-5, B co -doping enhances the activity of the faradic reaction of carbon electrodes in KOH electrolyte. Furthermore, the fabricated Zn-ion hybrid supercapacitor (ZHSC) based on this carbon electrode delivers a highenergy density of 140.7 W h kg -1 at a power density of 840 W kg -1 .