Jiménez-García Juan C, Olmos-Asar Jimena A, Franceschini Esteban A, Mariscal Marcelo M
Instituto de Investigaciones en Fisico-Química de Córdoba (INFIQC) - CONICET, Córdoba, Argentina.
Departamento de Química Teórica y Computacional, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina.
Phys Chem Chem Phys. 2021 Dec 15;23(48):27543-27551. doi: 10.1039/d1cp03731e.
Despite the great scientific effort, there are still some aspects of a polymeric membrane-based fuel cell (PEMFC) operation that are difficult to access experimentally. This is the case of the so-called triple-phase boundary (TPB), where the ionomer (commonly Nafion) interacts with the supported nanocatalyst (commonly Pt) and is key to the catalytic activity of the system. In this work, we use molecular dynamics simulations and electrochemical experiments on a Nafion/Pt/C system. We perform a systematic analysis, at an atomistic level, to evaluate the effect of several fundamental factors and their intercorrelation on the electrochemically active area (ECSA) of the catalysts. Our results reveal that at high Nafion contents, the catalyst utilization is affected due to the strong interaction between the sulfonic groups of the ionomer and the surface of the Pt nanoparticles (NPs). On the other hand, when the hydration level of the membrane decreases, the sulfonic groups have a greater occupation on the NP surface, covering the active area with hydrophobic Nafion chains and therefore increasing the inactive area. Voltammograms can corroborate our calculations. Overall, this investigation allows us to rationalize how the catalyst utilization is affected, which is an important step in establishing the relationship between the environment and the effectiveness and durability of the PEMFC system.
尽管付出了巨大的科学努力，但基于聚合物膜的燃料电池（PEMFC）运行仍存在一些难以通过实验获取的方面。所谓的三相边界（TPB）就是这种情况，在三相边界处，离聚物（通常是Nafion）与负载型纳米催化剂（通常是Pt）相互作用，并且是该系统催化活性的关键。在这项工作中，我们对Nafion/Pt/C系统进行了分子动力学模拟和电化学实验。我们在原子水平上进行了系统分析，以评估几个基本因素及其相互关系对催化剂电化学活性面积（ECSA）的影响。我们的结果表明，在高Nafion含量下，由于离聚物的磺酸基团与Pt纳米颗粒（NPs）表面之间的强相互作用，催化剂利用率受到影响。另一方面，当膜的水合水平降低时，磺酸基团在NP表面的占有率更高，用疏水性的Nafion链覆盖活性区域，从而增加了非活性区域。伏安图可以证实我们的计算。总体而言，这项研究使我们能够阐明催化剂利用率是如何受到影响的，这是建立环境与PEMFC系统有效性和耐久性之间关系的重要一步。
