Coarse-Grained Molecular Dynamics Simulation of Ionomer-Mediated Carbon Cluster Bonding in Polymer Electrolyte Fuel Cell Catalyst Layers

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In the field of sustainable energy technologies, Polymer Electrolyte Fuel Cells (PEFCs) represent a crucial advancement for achieving high-efficiency power generation. This study focuses on the specific behavior of ionomers within PEFCs, particularly how they facilitate the bonding of carbon clusters during the evaporation process, critical for the structural integrity and functionality of the catalyst layer. Amid the global shift toward a hydrogen economy, the development of robust and efficient PEFC technologies is imperative. The Nafion membrane, developed by DuPont, is the standard bearer for proton exchange membranes due to its superior proton conductivity, chemical stability, and durability. Despite these advantages, the performance of PEFCs under high temperature and low humidity conditions remains a challenge due to the reduced efficiency of proton transport. This research concentrates on the micro-mechanics of how ionomers assist in the bonding between carbon clusters during the drying stages of film formation, aiming to overcome this efficiency bottleneck. Employing Coarse-Grained Molecular Dynamics (CGMD) simulations, our study delves into the detailed interactions between ionomers and Pt-carbon clusters during evaporating solvents. The simulations use a refined computational model to capture the dynamic interplay during evaporation conceptualized as micro-differentiated boxes within the system as illustrated in Figure 1. These boxes allow for the analysis of ionomer behavior on a flat, graphene-sheet-modeled cluster surface adorned with Pt particles, assessing how different configurations influence structural and transport properties. This approach not only elucidates the role of ionomers in promoting the aggregation of carbon clusters during evaporation but also provides insight into the nuanced processes that govern the formation and stability of the catalyst layer. Initial simulations pointed out the need for adjustments in the force field settings, which were subsequently optimized to enhance the accuracy of the observations regarding ionomer distribution and bonding effectiveness during evaporation. With the foundational simulations set, future work will extend to exploring how various experimental conditions—such as solvent composition, and the size and density of platinum particles—affect ionomer bonding between carbon clusters. By adjusting these parameters systematically, we aim to define the optimal conditions that enhance the structural cohesion and functional performance of the catalyst layer. This investigation is expected to yield significant insights into the fundamental interactions and mechanisms at play in the bonding process, contributing to a deeper understanding of PEFC technology and leading to advancements in the production methods of these fuel cells. Ultimately, this research will help to refine and optimize the procedures for manufacturing more efficient and durable PEFCs, marking a substantial step toward more sustainable energy systems. Acknowledgment The New Energy and Industrial Technology Development Organization (NEDO) of Japan supported this work under Grant number NP20003. A part of the results was obtained by supercomputer system of Institute of Fluid Science, Tohoku University. Figure 1

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