Amorphous vanadium oxide/carbon composite (V2O5/C) was first applied to the positive electrode active material for rechargeable aluminum batteries. Electrochemical properties of V2O5/C were investigated by cyclic voltammetry and charge–discharge tests. Reversible reduction/oxidation peaks were observed for the V2O5/C electrode and the rechargeable aluminum cell showed the maximum discharge capacity over 200 mAh g–1 in the first discharging. The XPS analyses after discharging and the following charging exhibited that the redox of vanadium ion in the V2O5/C active material occurred during discharging and charging, and the average valence of V changed between 4.14 and 4.85.Keywords: aluminum; amorphous vanadium oxide; dipropylsulfone; multivalent cation battery; rechargeable aluminum battery; rechargeable battery; vanadium oxide

•PdAg and PdAu nanoparticle catalysts were prepared by a wet method without no purification.•PdAg/CB had lower onset potential of glycerol oxidation than Pd/CB due to electronic effect.•PdAg/CB exhibited higher durability for lower potentials than Pd/CB.•PdAu/CB had higher glycerol oxidation current than Pd/CB due to bi-functional effect.•PdAu/CB exhibited higher durability for higher potentials than Pd/CB and PdAg/CB.PdAg and PdAu alloy nanoparticle catalysts for the glycerol oxidation reaction (GOR) were prepared at room temperature by a wet method. The molar ratio of the precursors controlled the bulk composition of the PdAg and PdAu alloys, and their surface composition was Ag-enriched and Pd-enriched, respectively. On PdAg-loaded carbon black (PdAg/CB) electrodes, the onset potential of GOR was 0.10–0.15 V more negative than on the Pd/CB electrode due to the electronic effect. The ratio of GOR peak current densities in the backward and forward sweeps of CVs (ib/if) was smaller because of the improved tolerance to the poisoning species. The ratio of the GOR current density at 60 and 5 min (i60/i5) for the PdAg/CB electrodes was higher for more negative potentials than the Pd/CB electrode. In contrast, the PdAu-loaded CB (PdAu/CB) electrodes had an onset potential of GOR similar to the Pd/CB electrode and a higher GOR peak current density owing to the bi-functional effect. However, the ib/if ratio was higher for PdAu/CB because of the increase in ib as the Pd surface was recovered, and the i60/i5 ratio was higher for more positive potentials, similar to the Pd/CB electrode.

•A new NiO positive electrode with noble electrochemical anodization method was prepared.•NiO electrode was sandwich structure with a pair of 2∼3 μm thick NiO layers and 2 μm thick Ni metal.•Hybrid capacitor was constructed with the NiO electrode, an activated carbon, and 10 M KOH.•A maximum specific energy was 16 W h kg−1 and a specific power was 22.2 kW kg−1.A NiO positive electrode for aqueous hybrid capacitors was prepared by a new galvanostatic anodization method. A thin sheet of heat-treated Ni was galvanostatically oxidized in aqueous 85% H3PO4 containing 0.5 M NH4F. During the anodization, the thickness of the Ni metal sheet decreased from 10 to 2 μm and 2- to 3-μm-thick NiO layers were formed on both sides of the Ni metal sheet. A hybrid capacitor comprising the anodized NiO positive electrode, an activated carbon negative electrode, and aqueous 10 M KOH exhibited a maximum specific energy of 16 W h kg−1 and a specific power of 22.2 kW kg−1.A new NiO positive electrode with noble electrochemical anodization method was prepared. NiO electrode was sandwich structure with a pair of 2∼3 μm thick NiO layers and 2 μm thick Ni metal.