We have succeeded in preparing ordered-and disordered-Pt 3 Co nanoparticles supported on carbon black (CB), with the nearly identical particle size distribution, by the nanocapsule method with heat-treatment at high temperatures. The temperature dependences of the oxygen reduction reaction (ORR) activities at two kinds of Pt 3 Co/CB catalysts were examined in O 2 -saturated 0.1 M HClO 4 solution by the multi-channel flow double electrode (M-CFDE) technique. For the ordered-Pt 3 Co/CB, the apparent rate constant k app (per unit active area) for the ORR increased with elevation of the temperature up to 65 • C and stabilized at nearly the same value as that for commercial c-Pt/CB at 80 • C, due to a severe dealloying of the Co component in the hot acid solution. In contrast, the k app values at the disordered-Pt 3 Co/CB were higher than those of the ordered-Pt 3 Co/CB over the whole temperature range from 30 • C to 80 • C. The disordered-Pt 3 Co/CB also exhibited higher stability than the ordered-Pt 3 Co/CB for both an accelerated durability test (ADT, by standard potential step cycles between 0.6 V and 1. The polymer electrolyte fuel cell (PEFC) is anticipated to be one of the most promising, clean, and energy-efficient power sources for fuel cell vehicles (FCVs) and stationary cogeneration systems (FCCGs). In 2014, a strategic roadmap for hydrogen and fuel cells was formulated by the Ministry of Economy, Trade, and Industry (METI) of Japan and was revised in 2016.1 For the large scale commercialization of both FCVs and FC-CGs in its Phase 1, it is necessary to reduce the system cost while maintaining the performance and durability. At the present stage, however, the use of substantial amounts of costly Pt cathode catalysts supported on carbon (Pt/C) is unavoidable to decrease the large overpotential for the oxygen reduction reaction (ORR). Hence, the development of the cathode catalysts having both high activity for the ORR and high durability is quite important. To improve the ORR activity, Pt-based catalysts alloyed with non-precious metal such as Fe, 2-6 Co, 2,4,7-11 and Ni, 2-13 have been investigated intensively. For nano-sized Pt-M alloy catalysts (Pt-M/C), the kinetically-controlled area-specific activity j k for the ORR was enhanced by ca. 2∼7 times compared to that of pure Pt. The enhancement factor has been found to depend on various properties of alloy nanoparticles, e.g., composition, 4,14-16 shape (or size), 17-21 and crystal structure. [22][23][24][25][26][27][28][29] For example, the values of j k for Pt-Co alloys showed a maximum at the atomic ratio of Pt/Co = 3. 4,5,14 It has been reported that the electronic structure of the Pt skin layer formed on Pt-M alloys could change with the composition of the underlying alloy, reaching a maximum at the optimum alloy composition or alloying metal species M. 24,[30][31][32] Because the surface is not perfectly covered with uniform Pt skin layer, j k often decreases appreciably by dealloying of M during the operation of PEFCs or electrochemical measurements...
The R&D of highly active and durable anode catalysts for the oxygen evolution reaction (OER) is very important for high efficiency Proton Exchange Membrane Water Electrolysis (PEMWE). The reason is that the high overpotential of OER reaction is the main factor of the energy loss. At present, the use of highly active and durable iridium catalyst is one of the resolutions for reducing overpotential. From the perspective of iridium production, not only is limited the producing area, but production amount is limited because iridium is by-product of PGM mine in South Africa. Therefore, in order to popularize hydrogen production by large-scale PEMWE, it is necessary to to achieve the high performance with the minimum amount of iridium material. In this study, we report the activity and durability of catalysts coated membranes (CCMs) based on the IrOx catalyst surface area and loadings. High surface area IrOx catalyst (SA100) and a low surface area IrOx catalyst (SA5) from Tanaka Kikinzoku Kogyo K.K. were used for OER catalysts in this study. These catalysts were characterized by ICP-AES analysis, powder XRD, N2-BET, and SEM images. CCMs were prepared by spray-coating and hot-press with IrOx catalysts at the anode and carbon supported platinum at the cathode (TEC10E50E, Tanaka Kikinzoku Kogyo K.K.). Single cell electrochemical analysis including initial polarization curves, cyclic voltammetry, and durability tests (at 50℃, 2A/cm2) and SEM cross section images was studied for all CCMs. The SEM images of the CCMs microstructure near the catalyst layer were shown in Figure 1-A and 1-B. The particle size of IrOx (SA100) was found to be ca.5nm. For IrOx (SA5), the particle size was less than 2nm. The cell voltages focused on the iridium loadings were confirmed in Figure 2-A and 2-B. Although there was significant difference in SEM cross section images of catalyst layers, the trend obtained for the SA100 was consistent with the trend in the SA5. The IrOx loaded from 0.1 to 0.3 mg/cm2 range exhibited a gradual increase in cell potential. Furthermore, the catalytic durability and CV studies using single cells at 2A/cm2, 50℃ will be discussed. This report will be one of the valuable source of information for CCM design for general PEMWE. Figure 1
In recent years, water electrolysis for hydrogen production is considered as a key technology to greenhouse gases reduction. In particular, PEM water electrolysis has the advantages of high efficiency, high current density and responsiveness to renewable energies. On the other hand, since a large amount of Pt and Ir metals are used in the PEM electrolyzer, it is necessary to reduce the amount of Pt and Ir metal used for the growth market in the future. In this study, we focused on the low Pt and Ir loading CCM with SA100(Ir catalyst) and TEC10E50E(Pt catalyst). CCMs were prepared by splay method, the SEM images of cross-section are shown in Figure. CCMs with different configurations for catalysts, ink process, and catalysts loadings were studied using particle size distribution analyzer, polarization curves, durability, and other electrochemical methods. Ir Oxide should behave two roles in the catalyst layer: conductor and catalyst. In the case of CCMs with controlled ink particle size, the cross-section images and IV performance were improved. Catalyst loading reduction partially improved the polarization curves, it had a negative effect on durability. Figure 1
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