Search

Nowadays, materials that possess high activity and natural oxygen vacancy have garnered significant attention as potential electrode materials for supercapacitors. In this study, we successfully prepared the Hf 6 Ta 2 O 17 (HTO) nanofibres (NFs) with an orthorhombic superlattice structure using the electrospinning technique and sintering process. The characterization results indicate that the HTO NFs synthesized at 750 °C show good micro nanostructures and outstanding electrochemical properties. To enhance its energy storage performance, additional oxygen vacancies (OVs) were introduced through a carbothermal treatment under an Ar atmosphere. Although longer reduction reaction times can produce more OVs, the integration of grain boundaries and the growth of grain size caused by large annealing times may limit its electrochemical performance. Therefore, the HTO NFs treated for 1 h (HTO/C-1) exhibited the maximum C s of 925 F·g−1 at 1 A·g−1 with a larger voltage window of 2.1 V. Furthermore, a symmetric supercapacitor fabricated by two reduced HTO NFs electrodes and 1 M Na 2 SO 4 solution, recorded as r-HTO NFs//r-HTO NFs. The device demonstrated excellent energy density of 73.3 Wh·kg−1 (at power density of 1050 W·kg−1) and a long cycling life (81.8% retained after 5000 cycles). These results suggest that the optimized reduction process can provide appropriate oxygen vacancies in HTO NFs, thereby effectively enhancing its performance. [Display omitted] • The Hf 6 Ta 2 O 17 (HTO) nanofibres (NFs) are synthesized by electrospinning method. • The micro nanostructures and electrochemical property of HTO NFs can be designed by controlling the synthesis temperature. • The carbothermal treatment carried under Ar atmosphere is used to improve the amount of oxygen vacancies of HTO NFs. • The HTO NFs treated of 1 h (HTO/C-1) presents excellent capacitance of 925 F·g−1 at 1 A·g−1. • The r-HTO NFs//r-HTO NFs device shows high energy density of 73.3 Wh·kg−1 at power density of 1050 W·kg−1. [ABSTRACT FROM AUTHOR]

We introduced the concept of a novel hybrid faradaic structure as a mechanism to improve the performance of biomass-derived carbon-based supercapacitors (SCs). Organic-inorganic hybrid composition, nanostructures, porosity, surface area and active redox reactions were carefully designed. We reported the facile, cost-effective and environmentally friendly fabrication of pure lignin carbon nanofibers (LCNFs) incorporated with flower-like, multi-metal and intrinsically capacitive (Ni-Co@MnO 2) nanoparticles in a flexible and binder-free electrode for SCs by the electrospinning technique using various electrolytes (1 M Na 2 SO 4 , 0.5 M KI and 1 M Na 2 SO 4 +0.5 M KI). Mechanically robust LCNFs were used as a free-standing electrode and characterized for electrochemical performance using a two-electrode system in a Swagelok cell. Specific capacitance of the LCNFs in 1 M Na 2 SO 4 electrolyte (current density 0.1 A/g) of 129 F/g increased to 200 F/g when adding 1 % manganese oxide nanoparticles that introduced intrinsic capacitance into the nanofibers. This value further increased to 303 F/g by adding 1 % Ni-Co to the manganese oxide. The nanoflower morphology significantly increased the surface area via micro and mesopore modification on carbonization and via macropore expansion on activation. After applying a mixed electrolyte (1 M Na 2 SO 4 + 0.5 M KI), the capacitance reached 400 F/g and remained stable up to 1000 GDC cycles. Using the same composite nanofibers, 1,021 F/g was achieved using 0.5 M KI as an electrolyte. However, the latter system appeared unstable beyond 200 GDC cycles, suggesting that it can be applied as a disposable fast-charge supercapacitor. In the presence of a chemically-stable, highly-porous and partially-conductive carbon matrix, we concluded that interplay between the multi-metal oxides and electrolytes increased oxidation numbers, thereby boosting the faradaic reaction and enhancing electronic conductivity. [Display omitted] • EDLC carbon-based supercapacitor was fabricated from flower-like Ni-Co@MnO 2 nanoparticles and biomass lignin. • The unique metal oxide nanostructure led to highly-porous carbon nanofibers with unblocked micro-, meso- and macropores. • Mixed electrolyte of Na 2 SO 4 and KI led to capacitance of 400 F/g up to 1000 GDC cycles. • With KI as electrolyte, capacitance of 1,021 F/g was achieved and stable up to 200 GDC cycles. [ABSTRACT FROM AUTHOR]