Microstructures and Proton Networks of Ionomer Film on the Surface of Platinum Single Atom Catalyst in Polymer Electrolyte Membrane Fuel Cells

Abstract

Pt single atom catalyst (SAC) is a promising catalyst material with ultrahigh Pt utilization efficiency and excellent electrochemical activity for PEMFCs. However, the performance of fuel cells with Pt SAC is still insufficient for practical applications, which is mainly resulting from the significant increasing proton and oxygen transport resistance in the catalyst layer. In this study, the microstructures and transport properties of ionomer film on the surface of Pt SACs are investigated by classic molecular dynamics (MD) simulations. It is found that the hydrated ionomer film can be divided into three regions including dense layer region, middle region, and top region. Hydrophilic components in dense layer region increase with higher Pt single atom loading, due to the rise of water affinity from the Pt−ionomer interface. Water clusters are mainly confined to the middle region. Besides, with the increase of Pt single atom loading, the interactions between hydrophilic and hydrophilic species are weaker. Side chains locate below or above the continuous water clusters show upward or downward configurations, heading to the water surface. An appropriate loading of Pt SACs is essential for promoting the connectivity of hydrophilic clusters as well as the accessibility of protons to Pt SACs.

Perspectives on Challenges and Achievements in Local Oxygen Transport of Low Pt Proton Exchange Membrane Fuel Cells

“…It is the interfacial affinity that determines the distribution of the ionomer side chain, whereas the ionomer begins to be oriented parallel to the surface. Specifically, tends to adsorb on the metallic substrate, [ 23 ] thus forming a strong alignment and local densification near the ionomer–substrate interface, [ 23b,24 ] which makes the phase separation weaker.…”

Innovative Insight into O2/N2 Permeation Behavior through an Ionomer Film in Cathode Catalyst Layers of Polymer Electrolyte Membrane Fuel Cells

“…The hydration level λ is defined as the ratio of H 2 O and H 3 O + to the number of sulfonic anion groups. Herein, three hydration levels of λ = 4, 7, and 10 are adopted, ,− ,, correspondingly another 300, 600, and 900 H 2 O molecules are used, respectively. Then, the PFSA polymers, H 2 O, and H 3 O + are placed randomly on the surface of the Pt (111) slab to build the initial integrated models.…”

Plating of Ion‐Exchange Membranes: A Molecular Dynamics Study

“…You et al. [ 40 ] studied the performance of a novel, promising single‐atom platinum catalyst configuration, detailing the role of catalyst loading. Finally, Zhang and Ding [ 41 ] studied atomic arrangement, as well as transport of hydronium ions and water, as functions of the Nafion film thickness on the ionomer‐platinum interface.…”