Unilamellar crystallites of conductive ruthenium oxide having a thickness of about 1 nm were obtained via elemental exfoliation of a protonic layered ruthenate, H(0.2)RuO(2).0.5H(2)O, with an alpha-NaFeO(2)-related crystal structure. The obtained RuO(2) nanosheets possessed a well-defined crystalline structure with a hexagonal symmetry, reflecting the crystal structure of the parent material. The restacked RuO(2) nanosheets exhibited a high pseudocapacitance of approximately 700 F g(-1) in an acidic electrolyte, which is almost double the value of the nonexfoliated layered protonated ruthenate.

The structural kinetics of surface events on a Pt 3 Co/C cathode catalyst in a polymer electrolyte fuel cell (PEFC) was investigated by operando time-resolved X-ray absorption fine structure (XAFS) with a time resolution of 500 ms. The rate constants of electrochemical reactions, the changes in charge density on Pt, and the changes in the local coordination structures of the Pt 3 Co alloy catalyst in the PEFC were successfully evaluated during fuel-cell voltage-operating processes. Significant time lags were observed between the electrochemical reactions and the structural changes in the Pt 3 Co alloy catalyst. The rate constants of all the surface events on the Pt 3 Co/C catalyst were significantly higher than those on the Pt/ C catalyst, suggesting the advantageous behaviors (cell performance and catalyst durability) on the Pt 3 Co alloy cathode catalyst.

The metallization behavior of molecularly thin RuO2 nanosheets obtained from complete delamination of layered ruthenates was studied. Interestingly, the RuO2 nanosheets in a monolayer state topotactically transformed into a single layer of Ru atoms, i.e., ruthenium metal nanosheets, which can be regarded as a new family of nanosized metals.

The structural kinetics of surface events on a Pt/C cathode catalyst in a membrane electrode assembly (MEA) with a practical catalyst loading (0.5 mgPt cm(-2)) for a polymer electrolyte fuel cell were investigated by in situ time-resolved X-ray absorption fine structure analysis (XAFS; time resolution: 100 ms) for the first time. The rate constants of structural changes in the Pt/C cathode catalyst in the MEA during voltage cycling were successfully estimated. For voltage-cycling processes, all reactions (electrochemical reactions and structural changes in the Pt catalyst) in the MEA were found to be much faster than those in an MEA with a thick cathode catalyst layer, but the in situ time-resolved XAFS analysis revealed that significant time lags similarly existed between the electrochemical reactions and the structural changes in the Pt cathode catalyst. The time-resolved XAFS also revealed differences in the structural kinetics of the Pt/C cathode catalyst for the voltage-cycling processes under N2 and air flows at the cathode.

Synthesis of composition-controlled mesoporous Pt-Ru alloy fibers by a dual-templating method (Yamauchi et al. J. Am. Chem. Soc., 2008, 130, 5426-5427) is demonstrated using lyotropic liquid crystals (LLCs) as mesostructural direct templates and porous anodic alumina membranes (PAAMs) as morphological direct templates. The LLCs, including Pt and Ru species, were formed from diluted precursor solutions inside PAAM channels via the evaporation-mediated direct templating (EDIT) method. For all Pt-Ru compositions, the tubular mesophases in the LLCs were stacked like donuts within the PAAM channels because of the confined effect. After metal deposition by the vapor infiltration method of dimethylamineborane (DMAB) and subsequent removal of both surfactants and PAAM, mesoporous Pt-Ru fibers with various compositions were successfully prepared. Both the alloy state and the mesoporous structures were fully characterized by high-resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopic (EDS) mapping, X-ray photoelectron spectroscopy (XPS), and electrochemical techniques. The composition ratios of Pt and Ru in the fibers were tuned by controlling those of the used precursor solutions. The mesoporous structures in the fibers reflected the original LLC mesostructures; however, the ordering of the mesoporous structures gradually decreased with the increase in the Ru contents in the precursor solutions.