Weibo Zheng

Shear intensity and temperature during the dispersion of catalyst ink significantly influence the agglomerate structure and rheological properties of the ink. Taking Pt/C catalyst ink as the research subject, this work investigates the motion behavior and agglomeration characteristics of catalyst micro/nanoparticles from a mesoscopic perspective. Based on the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory, the lattice Boltzmann method (LBM) is employed to simulate the motion behavior of ink particles under different Reynolds numbers (100, 800, and 1500) and temperatures (20 °C, 30 °C, and 40 °C), and validation tests are also conducted. It is found that under high shear intensity, the system exhibits a higher relative effective viscosity and a more uniform distribution. The system tends to form small “chain-like” agglomerates or become completely broken apart by shear. In contrast, under low shear intensity, clusters are more likely to form large “ellipsoidal” agglomerates that are non-uniformly distributed in the flow field. Moreover, increasing temperature intensifies the thermal motion of particles, making it easier to overcome interparticle forces. In the simulation domain, elevated temperature contributes to a more uniform distribution of agglomerates within the system. This work elaborates how shear intensity and temperature variation influence the dispersion of micro/nanoparticles in catalyst ink, providing support for the preparation of catalyst ink.

High-temperature (>100 °C) operation of proton exchange membrane fuel cells simplifies water and thermal management, accelerates electrode kinetics, and improves impurity tolerance. However, the degradation mechanism of the membrane electrode assembly (MEA) under such conditions remains unclear. Here, a high-temperature-resistant MEA based on a phosphoric–sulfonic acid copolymer membrane is investigated through an accelerated stress test at 105 °C for 50 h. The initiation and propagation of crack networks within the cathode catalyst layer are identified as a critical bottleneck in performance degradation. Mass transport loss is the most pronounced degradation mode. This loss arises from crack formation, ionomer degradation, and carbon corrosion. The MEA exhibits a voltage decay of 35.23% at 2 A cm–2 and an electrochemical surface area loss of 62.9%. Chemically, cracks initiate from the transformation of disordered carbon into ordered carbon in the carbon support (ID/IG decreasing from 1.1268 to 0.4735) and the detachment of sulfonic acid side chains from the ionomer (I1060/I1210 decreasing from 0.483 to 0.133). Physically, Ostwald ripening of platinum particles (mean size increasing from 3.48 to 4.29 nm) and stress concentration induced by temperature and humidity cycling drive crack growth. Finite-element simulations using a cohesive zone model reveal that cracks propagate steadily along the ionomer/catalyst interface─the path of least energy dissipation. This study establishes a direct link from microstructural evolution to macroscopic performance degradation. Crack network formation is highlighted as a key bottleneck. These findings provide guidance for material design and lifetime prediction of high-temperature-resistant MEAs.