The aim of the IGF project "3D-Kat" was to reduce the amount of the expensive catalyst metal platinum of a PEMFC, while maintaining constant or higher electrochemical performance by creating a three-dimensional structure in the cathode catalyst layer (KKS). The research project included the development of inkjet-compatible inks (catalyst ionomer dispersions, KID), the design of the cathode structure, the fabrication of the KKS by inkjet, the manufacturing of the membrane electrode assembly (MEA) and the subsequent electrochemical characterization. The development of the 3D structuring of the cathode, i.e. the distribution of platinum and the proton-conducting ionomer in the through-plane direction (perpendicular to the membrane) or the in-plane direction (fitting to the channels and ridges) has been supported by a numerical simulation using AVL FIRE™. Various KKS designs were created in the simulation, which were validated and optimized in the course of the project to better predict performance and efficiency.
The ink development initially included a screening of the individual components (solvent, Pt/C catalyst, ionomer) and the process parameters (dispersion method, duration and intensity). As a result, three KIDs with different platinum loadings and three KIDs with varying mass fraction of the proton-conducting ionomer were produced. The KKS was printed directly onto the membrane. Important structure-property relationships of the dispersion procedure with the resulting properties of the KID, their behaviour in the inkjet system and ultimately the influence on the electrochemical performance of the resulting MEA were analyzed. The in-plane structuring was based on the meandering structure of the channels of the flowfiel (see photo). To realize the structuring in the through-plane direction, the KIDs were printed layer by layer on top of each other. Varying the concentration of ionomer in the through-plane direction showed that increasing the concentration of ionomer near the membrane leads to an increase in the performance of the MEA, while decreasing the concentration of ionomer at this location leads to lower performance compared to an ungraded reference. These observations suggest the need for good proton conductivity in this critical region.
Based on the promising results, a follow-up project will focus on the scale-up in a roll-to-roll process, exploiting the strengths of inkjet technology. It promises, compared to conventional processes, a more material-efficient and flexible fabrication of structured PEMFC components.
Project information:
- IGF project no. 30 EWBG
- PEM fuel cells by inkjet printing (3D-Kat)
- Duration: 01.02.2018 - 31.12.2020
- AiF research association: FKM VDMA
Project partners:
- Chemnitz University of Technology, Institute for Print and Media Technology
- ZBT, Department for Electrochemical Components
