Effects of catalyst agglomerate shape in polymer electrolyte fuel cells investigated by a multi-scale modelling framework

Abstract

A multi-scale modelling framework is developed for the PEFC cathode electrode. Unlike the conventional agglomerate model, the effects of the microstructure of the agglomerate are numerically coupled to the fuel cell-scale model in this framework. This is performed through solving the agglomerate-scale model first and subsequently extracting and using the data required to generate the performance curves in the fuel cell-scale model. This enables one to freely investigate the structure of the agglomerate without being limited to the only three agglomerate shapes that can be investigated using the conventional agglomerate model: spheres, long cylinders with sealed ends and long slabs with sealed ends. The numerical studies conducted in this work using the developed framework have revealed that the performance of the cathode electrode is highly sensitive to the specific surface area of the agglomerate if the size of the latter is relatively large, i.e. of the order of 1000 nm. Namely, the maximum reported current density has increased by about 60% when changing from the 'large' spherical agglomerate to the 'large' cylindrical agglomerate. Also, it has been shown that a slight change in the structure of the agglomerate may significantly improve the fuel cell performance.

Influence of catalyst structure on PEM fuel cell performance – A numerical investigation

“…Additional assumptions are employed in this study in order to take into account the microstructure of the catalyst layers [10,28,39]:…”

Continuum Model to Define the Chemistry and Mass Transfer in a Bicarbonate Electrolyzer

“…The three-dimensional solid, liquid, and gas phases were represented as homogeneous, one-dimensional continuums with volume-averaged values for key properties (e.g., porosity, tortuosity, active surface area, and water saturation). Mass transfer was modeled in the through-plane direction because previous reports have shown that the flow channel and porous CL of flow electrolyzers promote relatively uniform mixing in the in-plane direction. , The governing equations (based on mass, momentum, and charge conservation) were solved simultaneously to quantify the steady-state concentrations of liquid species (H + , OH – , K + , CO 2 , HCO 3 – , and CO 3 2– ), gas species (CO 2 , CO, and N 2 ) as well as the rates of the CO2RR (eq ), the HER (eq ), and acid–base reactions (eqs , , , and ). The boundary conditions are summarized in Figure b.…”

Analytical modeling framework for performance degradation of PEM fuel cells during startup–shutdown cycles

“…most inuential parameter. Ismail et al 26 studied the inuence of the shape of agglomerates and found that slight changes in structure can substantially improve fuel cell performance. Carbon corrosion models focus on reactions and its inuencing factors and the strategy for mitigating corrosion, while agglomerate models provide ways to calculate performance.…”

“…Among them, the agglomerate model, which shows the best match with experimental data, 22 has been used more oen to study the related issues of CL in recent years. [23][24][25][26] Moein-Jahromi et al 21 used the agglomerate model to simulate the CL, and the results were compared with those of the homogeneous one. A set of parametric studies were performed, in which the agglomerate size was found to be the Fig.…”

“…A set of parametric studies were performed, in which the agglomerate size was found to be the most influential parameter. Ismail et al 26 studied the influence of the shape of agglomerates and found that slight changes in structure can substantially improve fuel cell performance.…”