| dc.description.abstract | Direct methanol fuel cells (DMFCs) have high energy conversion efficiency, low operating temperature, easy fuel-feeding and it is environmentally friendly. Platinum-based catalyst has been commonly used in DMFCs, but it suffered from high cost. Thus, development of effective catalyst support which argues the catalyst activity and reduces amounts of Pt loading becomes the primary goal.
According to previous literature, traditional supports which composed of carbon material, such as XC-72, were oxidized easily to CO2 in positive potential and limited catalysts life time. In view of this, a recent research trend is to substituted carbon by ceramic materials which possess several advantages on electrochemical, thermal stability and corrosion-resistance. We examined perovskite structure, LaTiO2N(LTON), as the support. Earlier study shows the band gap of LTON is about 2.1 eV, lower than 3.2eV of TiO2 which usually applies in fuel cell catalyst support and promises better electron conductivity. In addition, utilization of lanthanum element is synthesized in LTON to make perovskite structure. The kind of binary metal ceramics has particular properties so we expect to know whether LTON applies in fuel cell catalyst support
In our experiment, we have discovered Ce doped LTON can reduce Pt particle size. HR-TEM shows that the size of Pt NPs prepared with the composition of Ce0.1La0.9TiO2N(Ce0.1-LTON) exhibited smaller particles
(3.7 nm) than other molar ratio of Ce, and exhibited more efficient methanol oxidation reaction (MOR) because production of Ce-O-Pt bond affects nucleation in reducing metal step. However, platinum NPs in MOR suffers from CO poisoning. To solve the problem, we have introduced PtRu alloy NPs to support on Cex-LTON and discovered changing composition of Ce0.5-LTON exhibited more efficient MOR with higher mass current (184A/g per Pt).
HR-TEM also shows that the size of PtRu NPs was smaller particles(3.4nm) than other ratio of Ce. In the situation, it is complicated to get explanation when Ru is mixed in the system due to considering production of Ru-Ce complex in reduction environment. We just guess optimization of two competitive factor which are production of Ce-O-Pt and Ce-Ru complex is at the ratio amount.
The electron conductivity issue is not entirely resolved from the lower band gap, and other carbon materials such as XC-72 and electron conductive polymer PEDOT are still required to amend the conductivity deficiency. Better improvement are being explored to amend this situation.
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