Nanostructural Control and Performance Analysis of Carbon-Free Catalyst Layers Using Nanoparticle-Connected Hollow Capsules for PEFCs
Nanostructural Control and Performance Analysis of Carbon-Free Catalyst Layers Using Nanoparticle-Connected Hollow Capsules for PEFCs
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DOI：
10.1149/2.0971608jes
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发表时间：
2016
影响因子：
3.9
通讯作者：
H. Kuroki;Takanori Tamaki;Takeo Yamaguchi
中科院分区：
文献类型：
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作者：
H. Kuroki;Takanori Tamaki;Takeo Yamaguchi
本研究通过对催化剂油墨进行不同处理(超声处理或高压灭菌)所形成的离聚体形态(聚集态或非聚集态)来控制具有多孔中空胶囊结构的铂-铁纳米粒子催化剂的无碳阴极催化层的纳米结构，并研究了催化层纳米结构与燃料电池性能的关系。对胶囊催化层的结构和电化学分析表明，胶囊表面的纳米离聚体形态对氧的传质阻力有很大影响；充分膨胀和较厚的离聚体层会堵塞胶囊之间的间隙，减缓氧气向胶囊表面的扩散。因此，与超声形成的不均匀且部分较厚的涂层相比，通过高压灭菌形成的均匀而薄的离聚体涂层由于更低的氧气传质阻力而产生更高的电池性能。此外，当胶囊催化层的湿度增加时，离聚体层较薄，离聚体/胶囊比非常小，在高电流密度下会降低电池性能，这可能是因为催化层内部液态水的氧气传质阻力增加。因此，除了离聚体的形态外，胶囊催化剂层中的水管理对于进一步提高电池性能非常重要。
In this study, the nanostructures of the carbon-free cathode catalyst layers using connected platinum–iron nanoparticle catalysts with porous hollow capsule structures are controlled by the ionomer morphologies (aggregated or not) formed by different treatments (ultrasonication or autoclaving) to the catalyst inks, and the relationship between the catalyst-layer nanostructures and the fuel-cell performances is investigated. Structural and electrochemical analyses of the capsule catalyst layers reveal that the nanosized ionomer morphologies on the capsules strongly influence the oxygen mass-transport resistance; the fully-swollen and thick ionomer layer would cause blocking of the interspaces between the capsules and slow oxygen-diffusion to the capsule surfaces. Thus, the uniform and thin ionomer coating formed by autoclaving produces a higher cell performance due to lower oxygen mass-transport resistance, compared with the nonuniform and partially thick coating formed by ultrasonication. Moreover, the thinner ionomer layer with a very small ionomer/capsule ratio reduces cell performance at high current densities when the humidity at the capsule catalyst layer increases, probably due to the increased oxygen mass-transport resistance through liquid water inside the catalyst layer. Therefore, in addition to the ionomer morphologies, water management in the capsule catalyst layers is important for further improving cell performance.