Preparation of Mesoporous Pt−Ru Alloy Fibers with Tunable Compositions via Evaporation-Mediated Direct Templating (EDIT) Method Utilizing Porous Anodic Alumina Membranes

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.