This work presents the effect of different contents of graphene foam (GF) on the electrochemical capacitance of nickel phosphate Ni3(PO4)2 nano-rods as an electrode material for hybrid electrochemical energy storage device applications.

In this study, the synthesis of porous activated carbon nanostructures from peanut (Arachis hypogea) shell waste (PSW) was described using different porosity enhancing agents (PEA) at various mass concentrations via a two-step process. The textural properties obtained were depicted with relatively high specific surface area values of 1457 m2 g−1, 1625 m2 g−1 and 2547 m2 g−1 for KHCO3, K2CO3 and KOH respectively at a mass concentration of 1 to 4 which were complemented by the presence of a blend of micropores, mesopores and macropores. The structural analyses confirmed the successful transformation of the carbon-containing waste into an amorphous and disordered carbonaceous material. The electrochemical performance of the material electrodes was tested in a 2.5 M KNO3 aqueous electrolyte depicted its ability to operate reversibly in both negative and positive potential ranges of 0.90 V. The activated carbon obtained from the carbonized CPSW:PEA with a mass ratio of 1:4 yielded the best electrode performance for all featured PEAs. The porous carbons obtained using KOH activation displayed a higher specific capacitance and the lower equivalent series resistance as compared to others. The remarkable performance further corroborated the findings linked to the textural and structural properties of the material. The assembled device operated in a neutral electrolyte (2.5 M KNO3) at a cell potential of 1.80 V, yielded a ca. 224.3 F g−1 specific capacitance at a specific current of 1 A g−1 with a corresponding specific energy of 25.2 Wh kg−1 and 0.9 kW kg−1 of specific power. This device energy was retained at 17.7 Wh kg−1 when the specific current was quadrupled signifying an excellent supercapacitive retention with a corresponding specific power of 3.6 kW kg−1. These results suggested that peanut shell waste derived activated carbons are promising candidates for high-performance supercapacitors.

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For future development of environmentally friendly and sustainable electrode materials, novel orthorhombic vanadium pentoxide@carbon composites (V2O5@C-WHS, V2O5@C-R1HS and V2O5@C-R2HS) were synthesized using a green solvothermal process. From the SEM and...

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Vanadium dioxide (VO2) monoclinic nanosheets were synthesized by a solvothermal method and carbonized iron-polyaniline (C-FP) nanograins were prepared by pyrolysis of iron-polyaniline (PANI) mixture under nitrogen ambient. An asymmetric device (VO2//C-FP) was evaluated with VO2 and C-FP as positive and negative material electrodes in aqueous 6 M KOH electrolyte respectively. The asymmetric supercapacitor (VO2//C-FP) exhibited a 47 mA h g-1 specific capacity and a specific energy of 30 W h kg−1 with an associated specific power of 713 W kg−1 at a gravimetric current of 1 A g−1 in a potential window of 1.6 V. It also displayed an 89% energy efficiency after 10000 galvanostatic charge-discharge cycles with a large improvement after ageing test at a gravimetric current of 10 A g-1.