Fragmentation and reorganization of agglomerates in catalyst inks: Understanding the time-scale and temperature-dependent effects on the dispersion process

The time and temperature of the dispersive shear process of catalyst inks have a great influence on the agglomerate structure of the ink and the rheological properties of the ink. In this paper, three different catalyst inks were prepared at 20 °C, 30 °C and 40 °C, and tested using characterization such as rheological techniques, zeta (ξ) potential, and particle size measurements. As the temperature rises, the median particle size inside the ink at the end of shear was 400, 308.05 and 157.3 nm, and the zeta potential was −37, −33 and −25 mV, with a decrease in viscosity and a deterioration in thixotropy. The catalyst layers prepared from inks dispersed at different temperatures had the smallest cracks and the flattest surface at 30 °C, and the largest cracks, the largest contact angle, the roughest surface, and the poorest polarization properties at 40 °C. Through the comprehensive analysis of the experimental data, the fragmentation and reorganization processes of agglomerates during the internal dispersion of catalyst ink were revealed from the perspectives of time scale and temperature variation, respectively. This study provides an experimental basis for a deeper understanding of the dispersion performance of catalyst ink at different temperatures.