Currently, carbon black is widely used as an electrocatalyst support for polymer electrolyte fuel cells (PEFCs). However, electrochemical oxidation leads to degradation of this material. In contrast, tin oxide (SnO 2 ) is electrochemically stable even under strongly acidic conditions, and relatively high electronic conductivity can be achieved by doping with niobium (Nb-SnO 2 ), compared with other metal oxides. In this study, Nb-SnO 2 is composited with various conductive carbon fillers, including vapor-grown carbon fibers (VGCF), carbon nanotubes (CNT), and graphitized carbon black (GCB), followed by platinum nanoparticle decoration. These nanocomposite electrocatalysts are incorporated into membrane electrode assemblies (MEAs) and tested under PEFC operational conditions. The resulting fuel cells achieve high initial I-V performance up to 0.742 V at 0.2 A cm −2 (80 • C), as well as excellent cycling durability. In particular, MEAs fabricated with Pt/Nb-SnO 2 /VGCF cathode electrocatalysts exhibit remarkable durability, with only a 12.1% drop in cell voltage at 0.2 A cm −2 over 60,000 start-stop cycles, and a 42.9% drop over 400,000 load potential cycles, corresponding to the lifetime of a fuel cell vehicle (FCV). Platinum-decorated metal oxide electrocatalysts can simultaneously realize high catalytic activity and extended durability, not only in ex-situ half-cell measurements, but also in full cell conditions.

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Electrocatalyst layer in polymer electrolyte fuel cells (PEFCs) has complicated 3D nanostructure, and control and optimization of the structure are essential for higher cell performance. Carbon black supported cathode catalyst is widely used, whilst carbon support can be degraded through electrochemical oxidation on the cathode side. The use of Nb-doped SnO2 supports for Pt electrocatalysts prevents support corrosion, while the use of carbon nanotube (CNT) based conductive fillers assists electronic transport in the electrocatalyst layers. High I-V performance of membrane electrode assemblies (MEAs) using stable SnO2 supports deposited on conductive CNT fillers is successfully demonstrated under the strongly acidic PEFC operational condition.

The mechanical and thermomechanical behaviors of ferroic La0.6Sr0.4Co0.2Fe0.8O3–δ (LSCF) with different oxygen nonstoichiometries are investigated around room temperature. The effects of oxygen deficiency on these behaviors are discussed by comparing LSCFs annealed in air and Ar. X‐ray diffraction analysis and the scanning electron microscopy observation demonstrate that the formation of oxygen vacancy reduces the rhombohedral distortion in the lattice, resulting in the disappearance of ferroic domains of LSCF. The measurements of electrical conductivity at high temperatures confirm that LSCF annealed in Ar has a higher oxygen nonstoichiometry than the one annealed in air. The thermomechanical analysis and the uniaxial compression test reveal that the introduction of oxygen vacancies can significantly influence the ferroic characteristics of LSCF such as ferromagnetism and ferroelasticity, whereas the intrinsic lattice stability would remain unchanged.

The electrocatalyst layer of the polymer electrolyte fuel cell (PEFC) has a complicated three-dimensional nanostructure. In order to realize high fuel cell performance, optimization of the nanostructure of the electrocatalyst layer is essential. However, detailed observation of their nanostructures is still a scientific and technological issue. In this study, the observation and quantitative evaluation of the porous electrocatalyst layers using various materials are carried out by applying various image observation and processing procedures using the focused-ion-beam coupled scanning electron microscopy (FIB-SEM). The selection of suitable thresholding methods is found to be important in the quantitative evaluation of pore side distribution in PEFC electrocatalyst layers.