A template-assisted strategy to synthesize a dilute CoNi alloy incorporated into ultramicroporous carbon for high performance supercapacitor application

Abstract

Carbon is widely studied as an electrical double-layer capacitor (EDLC) electrode material due to its high specific surface area and good electronic conductivity. However, the low capacitance and energy density limit its further commercial applications. Herein, we report a facile and novel synthesis of dilute CoNi alloy nanoparticles embedded into ultramicroporous carbon (CoNi/UMCs) via a template-assisted strategy using SBA-15 as a template. The CoNi alloy serves as not only the electron collector to decrease the conductivity during tests, but also creates CoNi oxide/oxhydroxide on the alloy surface in an alkali solution, promoting redox reactions in pseudocapacitors, enhancing the performance of supercapacitors. Interestingly, the final morphology of the composite is not transferred from SBA-15 and the ultramicropores absolutely come from sucrose itself. However, the presence of SBA-15 can definitely enlarge the surface area of the CoNi/UMCs. After carefully tailoring the loading of CoNi, we find that 0.95% CoNi/UMCs exhibit a high surface area of 613 m² g⁻¹ with regular ultramicropores of 0.57 nm. Due to the synergistic effect of porous carbon and CoNi alloy, the unique 0.95% CoNi/UMCs exhibit a high specific capacitance of up to 268 F g⁻¹ at 0.25 A g⁻¹ in 6 M KOH aqueous solution and a high capacitance retention ratio of 97.8% after 10 000 cycles.