In the first months the main goal was to commission the test station (single cell tester). This included adding and changing some of the sensors (new, more accurate mass flow controllers needed) and hardware for data transfer and logging (programmable logic controller - PLC), adding electrochemical impedance spectroscopy (EIS), software updates for control and regulation of the test setup (temperature control and test sequence functionality).
Initial measurements were made according to the in-house factory acceptance test (FAT) for full size stacks. Over time the measurements showed that this FAT needs to be changed for the single cell tester therefore it was modified to provide additional data of interest. These changes included:
a) performance testing at various compression pressures on the MEA
b) air and H2 utilisation tests performed at low- and high-current densities
c) addition of EIS
d) logging of data at constant current operation for extended period of time (short term durability tests)
Testing of MEAs was done on two different designs. One is a standard MEA used in the commercial fuel cell systems sold to customers and the other is an experimental one and is made in-house. The two main components of every MEA are:
a) electrodes made of carbon fibre gas-diffusion layer (GDL) which is coated with a catalyst layer (CL) based on platinum particles,
b) the proton exchange membrane (PEM) made of polymer doped with phosphoric acid.
For the standard MEAs these components are supplied by external partners. They are assembled together into a MEA in a German branch of the company located in Achern. On the other hand, the company produces its own in-house developed MEAs with a purpose to achieve the same performance and durability as standard MEAs, while focusing on reduction of costs and environmental impacts. This is a challenging task since changing the material of one component or only changing the composition of a material can introduce significant differences in the performance of the product. There are three major differences between standard and experimental MEAS:
a) In standard MEAs the GDL is made of woven carbon cloth while in experimental a thinner and cheaper non-woven carbon fibres are used
b) The PEM has high acid content which in terms of proton conductivity is good. But the acid also tends to leaches out which blocks the active sites of the catalyst. Therefore, the experimental MEAs are tested at different levels of acid doping to see the effect.
c) The most crucial subcomponent is the CL. In the case of standard MEAs the received GDL is already coated with the CL, while in the in-house MEAs a special roll coating machine is used to coat the catalyst ink onto the GDL. Here the research is mainly focused on:
- Ratio of binders, additives and solvents to achieve proper hydrophobicity, porosity, and thickness of the CL
- Reducing the Pt loading
By introducing the novel experimental setup commissioned within this project research and development and also quality control activities have gained significant boost. The exploitation of the project results can already be seen in:
- Reliable and accurate operation of the test setup
- Capability of faster testing cycles for new MEA components and production processes
- Based on the great success of this project the company decided to invest in additional test setups of this kind to increase its testing capabilities.
The company also collaborates well with the local Aalborg University (AAU), either in joint research projects or supplying materials for research and testing purposes. This collaboration has also contributed to the publication of the scientific article
https://doi.org/10.3390/en14112994(öffnet in neuem Fenster) and more are expected.
