A novel and hierarchical porous but cross-linked copper-doped biomass graphene (Cu@HPBG) combined with Nb2O5 (denoted as Nb2O5/Cu@HPBG) is successfully fabricated on a large-scale using fig peels as biomass carbon and copper as the graphitization catalyst. During the synthesis process, basic copper carbonate serves dual functions of pore-forming agent, as well as homogeneous copper provider, and NH3 is employed as a defect-forming agent and N dopant. Owing to the porous hierarchical structure increased availability of contact interface and pseudo capacitance active sites provided by copper and Nb2O5, the assembled asymmetrical supercapacitor (ASC) employing Nb2O5/Cu@HPBG as positive electrode and HPBG as negative electrode can not only widen the stability window range of 0～1.9 V, but also deliver a maximum gravimetric energy density of 82.8 W h kg-1 at the power density of 950.0 W kg-1 and maintain a remarkable cycling stability of 97.1% after 15,000 cycles. Impressively, due to the synergistic enhancement of Cu@HPBG and Nb2O5, the resulting Nb2O5/Cu@HPBG hybrid displays more positive half wave potential (∼0.85 V) and a long-life stability than Pt/C electrode toward oxygen reduction reaction (ORR). Our research provides a feasible strategy to fabricate renewable biomass graphene electroactive composites for large-scale supercapacitor electrodes and efficient ORR catalysts toward energy applications.
Keywords: Asymmetric supercapacitor; Graphitization catalyst; Hierarchical porous biomass carbon; Nitrogen-doped; Oxygen reduction reaction.
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