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Abstract: Nanostructures consisting of TiO2 particles as a core and carbon as a shell (TiO2@C) were prepared by heat treatment of TiO2 nanoparticles at 700 or 900°C in a methane atmosphere. X-ray diffraction and transmission electron microscopy showed that a carbon shell layer was formed whose thickness increased with increasing reaction temperature. These structures were used as supports for platinum nanoparticles and the hybrid particles exhibit improved catalytic activity and stability toward methanol electrooxidation compared to Pt on a carbon black (Vulcan XC-72R). It is likely that enhanced catalytic properties of the Pt on TiO2@C could be due to the stability of the core–shell support in comparison with carbon black support. [Copyright &y& Elsevier]

Abstract: We report nanostructured supports prepared by heat treatment of TiO2 nanoparticles at 700, 800, or 900°C under ammonia atmosphere. From X-ray diffraction analysis, it is found that the phase transformation of the supports from antase and rutile TiO2, TiO to TiN (TiO2 heated at 900°C, TiO2-900) is observed. In particular, the Pt on TiO2-900 (Pt/TiO2-900) exhibits such an excellent catalytic activity toward methanol electrooxidation compared to the Pt on Vulcan XC-72. It is likely that enhanced catalytic properties of the Pt/TiO2-900 may be attributed to stability of nitride support and interaction between Pt catalyst and nitride support, which are confirmed by cycling test of supports and X-ray photoelectron spectra of Pt catalysts. [Copyright &y& Elsevier]

Abstract: The corrosion resistance of carbon black, carbon nanofiber and carbon nanocage used as catalyst supports in fuel cells was investigated by monitoring CO2 emission using on-line mass spectrometry when 1.4V was applied for 30min. The changes associated with the carbon corrosion were assessed through electrochemical methods. In general, graphitized carbon supports were more corrosion-resistant than amorphous carbon black. However, the degree of graphitization did not directly correlate with higher resistance to corrosion. Hydrophobicity was critical in enhancing resistance to corrosion. When sintering of Pt particles was considered, carbon nanocages were more resistant than nanofibers. The present findings thus indicate that the carbon nanocage is an appropriate catalyst support in fuel cell systems. [Copyright &y& Elsevier]

Abstract: The electrochemical corrosion of carbon catalyst supports in polymer electrolyte membrane (PEM) fuel cells is investigated by monitoring the generation of CO2 using an on-line mass spectrometer at a constant potential of 1.4V. Our results suggest that carbon supports with a high degree of graphitization are more corrosion-resistant, which results in a dramatic improvement of the catalyst durability. We also show that CO2 measurements performed using on-line mass spectrometry represent a time-effective and reliable method for studying the electrochemical corrosion of carbon supports in PEM fuel cells. [Copyright &y& Elsevier]

Abstract: Nitrogen-modified carbon nanofibers to be used as catalysts in the oxygen reduction reaction (ORR) were synthesized by pyrolysis in the presence of cobalt with PPy and a chelating agent, such as ethylenediamine (ED). It has been found that the type of nitrogen source has a remarkable impact on the catalytic activity and stability of ORR catalysts. XPS and elemental analysis indicated that the combination of ED and PPy as nitrogen sources provided a synergistic effect toward increasing the total nitrogen content of the catalysts and the content of useful nitrogen functional groups such as pyridinic-N and graphitic-N that are responsible for high ORR activity and stability in acidic environments. [Copyright &y& Elsevier]