Instability of Pt/C electrocatalysts in proton exchange membrane fuel cells - A mechanistic investigation
Instability of Pt/C electrocatalysts in proton exchange membrane fuel cells - A mechanistic investigation
复制标题
DOI：
10.1149/1.2050347
复制
发表时间：
2005-01-01
影响因子：
3.9
通讯作者：
Gasteiger, HA
中科院分区：
文献类型：
--
作者：
Ferreira, PJ;la O', GJ;Gasteiger, HA
在80℃条件下，Pt/C电催化剂样品在0.5 M H2SO4中溶解的平衡铂浓度随着电位从0.9 V增加到1.1 V而增加。此外，在开路电压（约0.95 V）下工作的短堆质子交换膜燃料电池（pemfc）的铂表面积损失高于在负载（约0.75 V）下工作的短堆质子交换膜燃料电池。这两项发现都表明，可溶铂物质（如Pt2+）的形成对铂在PEMFC电极中的表面损失起着重要作用。由于在电位循环时观察到阴极中铂的加速表面积损失(在类似100小时内从63 m(2)/g（Pt）增加到23 m(2)/g(Pt))，因此通过入射角x射线衍射和透射电子显微镜（TEM）详细检查了循环膜电极组件（MEA）阴极，以揭示导致观察到的铂损失的过程。在本研究中，Pt/C催化剂和MEA阴极截面样品的TEM数据和分析明确地证实了铂颗粒的粗化发生在两个不同的过程中：(1)纳米尺度上碳上的奥斯特瓦尔德成熟，导致铂颗粒在碳上从3 nm左右粗化到6 nm左右；(2)微米尺度上可溶铂在离聚物相中的迁移，通过H-2分子交叉使这些物质发生化学还原，以及铂颗粒在阴极离聚物相中的沉淀，降低了铂在碳上的重量。据估计，每个过程贡献了类似的50%的整体铂面积损失的电位循环电极。(c) 2005电化学学会。
Equilibrium concentrations of dissolved platinum species from a Pt/C electrocatalyst sample in 0.5 M H2SO4 at 80 degrees C were found to increase with applied potential from 0.9 to 1.1 V vs reversible hydrogen electrode. In addition, platinum surface area loss for a short-stack of proton exchange membrane fuel cells (PEMFCs) operated at open-circuit voltage (similar to 0.95 V) was shown to be higher than another operated under load (similar to 0.75 V). Both findings suggest that the formation of soluble platinum species (such as Pt2+) plays an important role in platinum surface loss in PEMFC electrodes. As accelerated platinum surface area loss in the cathode (from 63 to 23 m(2)/g(Pt) in similar to 100 h) was observed upon potential cycling, a cycled membrane electrode assembly (MEA) cathode was examined in detail by incidence angle X-ray diffraction and transmission electron microscopy (TEM) to reveal processes responsible for observed platinum loss. In this study, TEM data and analyses of Pt/C catalyst and cross-sectional MEA cathode samples unambiguously confirmed that coarsening of platinum particles occurred via two different processes: (i) Ostwald ripening on carbon at the nanometer scale, which is responsible for platinum particle coarsening from similar to 3 to similar to 6 nm on carbon, and (ii) migration of soluble platinum species in the ionomer phase at the micrometer scale, chemical reduction of these species by crossover H-2 molecules, and precipitation of platinum particles in the cathode ionomer phase, which reduces the weight of platinum on carbon. It was estimated that each process contributed to similar to 50% of the overall platinum area loss of the potential cycled electrode. (c) 2005 The Electrochemical Society.