Rational hybrid modulation of P, N dual-doped holey graphene for high-performance supercapacitors

A P, N dual-doped holey graphene (PNHG) material is prepared by a scalable, facile synthetic approach, using a mixture of glucose, dicyandiamide (DCDA), and phosphoric acid (H₃PO₄). H₃PO₄ successfully functions as an “acid catalyst” to encourage the uniform breakage of C=C bonds to create large, localized perforations over the graphene monolith. Further acid treatment and annealing introduce in-plane holes. The correlation between the capacitance of the PNHG and its structural parameters during the fabrication process is comprehensively evaluated. A thermally induced sp²→sp³ transformation occurs at high temperatures because of the substantial loss of graphitic sp²-type carbons, together with a dramatic reduction in capacitance. The target PNHG-400 electrode material delivers exceptionally high gravimetric capacitance (235.5 F g⁻¹ at 0.5 A g⁻¹), remarkable rate capability (84.8% at 70 A g⁻¹), superior capacitance retention (93.2 and 92.7% at 10 and 50 A g⁻¹ over 25000 cycles, respectively), and acceptable volumetric capacitance due to moderate density, when it is used with organic electrolytes in the voltage range between 0 and 3 V. These results suggest a pioneering defect-engineered strategy to fabricate dual-doped holey graphene with valuable structural properties for high-performance electric double layer supercapacitors, which could be used in next-generation energy storage applications.