Juntaro Seki

A highly efficient Li2O2 oxidation system in Li–O2 batteries

A novel indirect charging system that uses a redox mediator was demonstrated for Li-O2 batteries. 4-Methoxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl (MeO-TEMPO) was applied as a mediator to enable the oxidation of Li2O2, even though Li2O2 is electrochemically isolated. This system promotes the oxidation of Li2O2 without parasitic reactions attributed to electrochemical charging and reduces the charging time.

Improved Performance of Solid-State Dye-Sensitized Solar Cells with CuI: Structure Control of Porous TiO2 Films

By increasing the pore and particle size of porous TiO2 films, the photovoltaic properties of solid-state dye-sensitized solar cells were dramatically improved. We analyzed the relation between the photovoltaic property and the microstructure of TiO2/Dye/CuI measured by scanning electron microscopy of the cross section of the cells. The larger pore size of the TiO2 films improved the CuI filling and the high degree of filling improved the short-circuit current density. Multilayered TiO2 films consisting of a TiO2 layer with small TiO2 particles and a second layer with larger TiO2 particles gave a power conversion efficiency under 1 sun of 6.0%.

The Native Oxide on Titanium Metal as a Conductive Model Substrate for Oxygen Reduction Reaction Studies

AbstractVery thin Pt layers on inexpensive substrates are promising oxygen reduction reaction (ORR) catalysts for polymer electrolyte fuel cells (PEFCs). TiOx is considered a suitable substrate but shows problems with conductivity, thus masking chemical effects by semiconductor effects (mismatch in energy states hindering electron transport). The native oxide on metallic Ti (TiOx/Ti) has been used as a novel and promising model substrate for ORR studies eliminating semiconductor effects. A high-coverage “particle” layer with high specific ORR activity was formed via electrodeposition from Ar-saturated solution. While high specific activities could be demonstrated, the concept could not be enhanced to high mass activities by limiting the Pt deposition amount. The approach to quench Pt deposition by introducing CO failed due to its adsorption to the TiOx/Ti substrate before metal deposition and thus the prevention of layer formation. A similar approach for the Pt/Au codeposition was also unsuccessful manifesting the TiOx/Ti-CO incompatibility even further. Graphical AbstractCO, blessing, and curse: Pt deposition from Ar-saturated solution leads to a “film”-like deposit with high specific ORR activity. In contrast, the corresponding CO-saturated solution leads to deposition termination but a smooth monolayer is not formed due to interaction of CO with the TiOx/Ti substrate and, consequently, very low ORR activity is obtained.