•All Ti–V–Cr–Ni alloys consist of Ti- and V-rich primary phase and V- and Cr-rich secondary phase.•Lattice volume of the primary phase influences the maximum discharge capacity.•Cycle durability of the alloy electrodes depends on the Cr content in the primary phase.•Their high-rate dischargeability depends on the Ni content in the secondary phase.TiV2.1−xCrxNi0.3 (x = 0.1–0.6 and 1.0), TiyV1.7Cr0.4Ni0.3 (y = 0.9–1.1) and TiV1.7Cr0.4Niz (z = 0.3–0.5) alloys were prepared by arc-melting, and their negative electrode properties such as the maximum discharge capacity (Cdis), charge–discharge cycle performance and high-rate dischargeability (HRD) were evaluated. All the alloys consisted of two phases. The V and Cr constituents were mainly distributed in the primary phase, whereas the Ti and Ni constituents were mainly distributed in the secondary phase. The Cmax was dependent on the lattice volume of the primary phase, mole fraction of the primary phase and the plateau potential in charging. The average decrement of discharge capacity (ΔCdis) from Cmax to the discharge capacity at 30th cycle was used as an indicator of charge–discharge cycle performance. The ΔCdis was decreased or cycle performance was improved with the Cr content in the primary phase. The discharge potential at DOD = 50% (ΔE50) was linearly changed with specific discharge current (idis), and the ΔE50/Δidis and charge transfer resistance (Rct) as indicators of HRD were decreased with an increase in the Ni content in the secondary phase.

•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.

Au nanoparticle-loaded carbon black (Au/CB) was prepared simply by bubbling CO as a reducing agent in a KAuCl4 aqueous solution containing polyvinyl alcohol as a stabilizer and then mixing Ketjen black as carbon black. X-ray diffraction spectra and transmission electron micrographs exhibited that the Au nanoparticles loaded on CB had the mean size of 3.3 nm which was scarcely increased even by the heat-treatment at 400 °C. For the Au/CB heat-treated at 400 °C (Au/CB-HT400), the modification of the Au nanoparticles with a Pt monolayer shell was performed by underpotential deposition of Cu and the following galvanic displacement with Pt. Cyclic voltammograms of Au–Pt1/CB-HT400 and Au–Pt2/CB-HT400 electrodes, which mean a Pt monolayer shell was deposited once and twice on Au/CB-HT400, indicated that 73 % and 97 % of the Au core nanoparticle surface were covered with the Pt shell, respectively. Koutecky–Levich plots made from hydrodynamic voltammograms of the Au–Ptx/CB-HT400 (x = 1, 2) electrodes exhibited that oxygen reduction reaction at both electrodes proceeded in four-electron mechanism like commercial Pt/CB. The mass activity at 0.9 V vs. RHE for Au–Pt1/CB-HT400 and Au–Pt2/CB-HT400 was ca. 5.1 and 4.4 times as high as that for the commercial Pt/CB, respectively. Moreover, in durability tests in which the square-wave potential cycling between 0.6 and 1.0 V vs. RHE was repeated 104 times, both catalysts were equivalent or superior to the commercial Pt/CB.

Various Pt-carbonyl cluster complexes ([Pt3(CO)3(μ-CO)3]n2- (n = 3–8)) were prepared by simply bubbling CO through PtCl62- solutions with different solvents. The number of layered Pt3(CO)3(μ-CO)3 units (n) was independent of water content and the length of the alkyl chain of the solvent, but it increased with a decrease in the permittivity of the solvent. The Pt-carbonyl cluster complexes were applied to the preparation of Pt-nanoparticle-loaded carbon black (Pt/CB). The mean size of the resultant Pt nanoparticles increased with n, whereas their size distribution remained narrow (±0.3 nm) irrespective of n. For the oxygen reduction reaction, the specific activity (SA) of each Pt/CB catalyst was almost equivalent to that of the Pt/CB catalyst produced by Tanaka Kikinzoku Kogyo (Pt/CB-TKK). Meanwhile, the mass activity (MA), the product of SA and real specific surface area (SSAreal), at 0.9 V of each Pt/CB catalyst was superior to that of Pt/CB-TKK because the SSAreal evaluated experimentally for the Pt/CB catalysts was higher than that for the Pt/CB-TKK. In particular, the MA at 0.9 V of the Pt/CB catalyst (Pt-et(50)/CB) prepared from [Pt3(CO)3(μ-CO)3]52- synthesized in ethanol–water (50:50 v/v) was about 1.7 and 2.0 times higher than those of commercial Pt/CB-TKK and E-TEK catalysts, respectively.Highlights► [Pt3(CO)3(μ-CO)3]n2- (n = 3–8) can be prepared in solvents with different permittivity. ► The number of layers of the prepared complexes increases as permittivity decreased. ► The mean size of Pt nanoparticles loaded on CB depended on number of layers. ► The size distribution remains narrow (±0.3 nm) irrespective of number of layers. ► Mass activity of Pt-et(50)/CB is higher than that of the commercial Pt/CB catalysts.

We have prepared NiO particles on Ni sheet and Ni foam substrates by chemical bath deposition and the following heat-treatment, and assembled a hybrid capacitor (HC) cell with the NiO-loaded Ni sheet or Ni foam positive electrode and activated carbon negative electrode. The deposited NiO particles had flower-like porous morphology which was composed of aggregated nanosheets. The maximum operating voltage of both HC cells was 1.5 V, which was much higher than theoretical decomposition voltage of water (1.23 V). The HC cell with NiO/Ni foam (HCfoam) had higher discharge capacitance and high-rate dischargeability and lower IR drop than the HC cell with NiO/Ni sheet (HCsheet) because of the increase in the utilization of NiO active material. Both energy and power densities per mass of active materials, were much higher than those for the HCsheet. Both HCfoam and HCsheet showed excellent cycle stability for 2000 cycles.

Pt nanoparticles-loaded carbon black (CB) was prepared from Pt carbonyl cluster complexes, and had much narrower size distribution than commercial Pt nanoparticles/CB. In the former the monodispersed Pt nanoparticles were highly dispersed on CB without aggregation even at high Pt loading of 80 wt.%. Hydrodynamic voltammograms in O2-saturated 0.05 M H2SO4 solution at 30 °C showed that the onset potential of oxygen reduction reaction (ORR) current for the monodispersed Pt nanoparticles/CB electrode was more positive than that for a polycrystalline Pt electrode and similar to that for the commercial Pt nanoparticles/CB electrode. Moreover, the mass activity for ORR for the monodispersed Pt nanoparticles/CB electrode was ca. 4.9 times higher than that for the commercial Pt nanoparticles/CB electrode, clearly indicating that the control of size distribution of Pt nanoparticles is meaningful for reducing the Pt consumption.