Transition-Metal Oxides Anchored on Nitrogen-Enriched Carbon Ribbons for High-Performance Pseudocapacitors

Increasing demand for effective energy-storage systems derived from low-cost and ecofriendly raw materials has aroused wide concern. In this contribution, we propose nitrogen-abundant amorphous micron-sized carbon ribbons (AMCRs) originating from biomass raupo as a novel substrate due to their specific quasi 2D morphologies and outstanding dispersion ability. Owing to the innate nitrogen atoms on the surface of AMCRs, ultrathin binary and ternary metal oxide (NiO, CoO, and NiCo₂ O₄ ) nanosheets can be uniformly developed under benign conditions. These three composites were separately fabricated as electrodes for supercapacitors in a three-electrode system and exhibited favorable activities. Among them, the ternary metal oxide composites NiCo₂ O₄ @AMCRs delivered the supreme specific capacitance of 1691 F g^-1 and best cycling stability (89 % capacity retention over 10,000 cycles). Moreover, symmetric supercapacitors (NiCo₂ O₄ @AMCRs//NiCo₂ O₄ @AMCRs) were assembled inside sleeve devices with 2 m KOH aqueous electrolyte, which demonstrated admirable cyclic stability (79.1 % capacity retention over 8,000 cycles), and an excellent energy density of 26 Wh kg^-1 at the power density of 1.8 kW kg^-1 .