[Final Blog Post] Research Abstract and Personal Reflection

Research Abstract

Climate change is considered one of the greatest issues of our time. It is a range of global phenomena mainly created by burning fossil fuels and releasing greenhouse gases. These phenomena include global warming, rising sea levels, melting of ice caps and glaciers, and extreme weather events. 

Fuel cells help mitigate climate change by offering a clean way to power vehicles on the road. Fuel cells convert chemical energy from the fuel used (usually hydrogen) and produce electricity without emitting greenhouse gases. However, they are not widely used as they still face durability, cost, and performance issues. Improving the latter without increasing the cost requires a better understanding of the materials and their integration in a fuel cell. Therefore, this summer I researched ionomers, a key material used in the electrodes of polymer-electrolyte fuel cells (PEFCs), a promising technology for transportation applications. Fuel-cell electrodes composed of catalysts and ionomers are prepared by casting and drying a solution (or dispersion) of these components. The ionomer exists as a film that facilitates transport of reactive species and acts as a binding agent for catalyst particles. In the catalyst layer, the ionomer is confined to nanometer thicknesses; this confinement affects ionomer properties such as transport and how much water it can absorb. Ionomer properties can be studied by casting them on a planar uniform wafer at nanometer thicknesses. I fabricated thin films, characterized the hydration behaviour of Nafion thin films, and gained insight on how the dispersion temperature affects the film’s swelling and behaviour. The effect of dispersion temperature on thin films has not been extensively studied, but it is important to know how dispersion temperature affects swelling and hydration since swelling is related to the conductivity of fuel cells; the greater the swelling the higher the conductivity (assuming there is no flooding).

Before investigating the effect of dispersion temperature on the swelling of thin films,  I first determined the weight of Nafion to use. To do this the swelling of films with different weight percentages was measured and a calibration curve was generated. The dispersions for the films were prepared using 70% water and 30% 1-propanol, and they were sonicated for 30 minutes at the same time as the silicon substrate was in the UV-ozone machine getting cleaned. The spin coater was then used to cast the films, which were then annealed in a vacuum oven at 150°C for an hour and finally placed in an ellipsometer for their swelling to be analyzed. 1.5wt% Nafion was chosen as the solid weight percent to be used in the project; it produced films of optimum thicknesses with consistent swelling. Then, I designed my own experiment to investigate the effect of dispersion temperature on the swelling of films. The film fabrication procedure was kept the same as the one used for the calibration curve, but this time, after sonicating the dispersions, they were heated for approximately 30 minutes in 35°C and 50°C water baths. The pH and temperature of the dispersion were measured over time to determine when the ionomer stabilizes. It was discovered that thin films cast from dispersions at higher temperatures have reduced swelling. As the dispersion heats, it becomes more acidic, suggesting the ionomer structure is changing. The reduced swelling may be due to these structural changes, but this requires further investigation.

The impact of annealing was also assessed by measuring the swelling of heated films that were both annealed and unannealed (dried at 50°C). It was found that unannealed films swell more than annealed films as during annealing the structure of the film is locked in. Annealing also had a greater impact on swelling than the different dispersion temperatures did. 

More research into dispersion temperature is still required to confirm them and to fully understand why films cast with hotter dispersions swell less. A lingering question regarding this research is why more acidic (hotter) dispersions cause films to swell less. The changes in structure of a dispersion when heated up and on the heated dispersion cast on the film still need to be further studied to reach a conclusion. However, the research done during this summer is a starting point for that study. 

Personal Reflection

With the covid-19 situation still being so uncertain, I was afraid, when thinking of my plans for summer earlier in the Spring 2021 semester, that I would not be able to plan anything. However, thanks to Cal Energy Corps I had the opportunity to work at LBNL in person during the summer, and, I am glad to say that my internship experience was very rewarding. 

At the start of my internship I had a very superficial understanding of what ionomer thin films were. Just before starting my internship I read a paper about ionomer thin films to familiarize myself with them. I found this paper quite complex and hard to understand, but very interesting. Thus, since I started working, all I did was ask questions about thin films, the results I was getting in the laboratory, and the different laboratory techniques used to research these films. I noticed that my understanding improved each time, but I still found it difficult to fully comprehend certain topics. I came to the realization that when doing research, sometimes you do not fully understand everything at first, it just requires work and patience.

Around the third week of my research, I became very frustrated. I was fabricating my films following the same procedure I had always been using but they did not give ideal results. I dealt with these poor films for about three days. The films themselves were shattered and could not even be put in the ellipsometer to analyze the swelling. I decided to take a step back and look deeper into why this was happening. After speaking to some grad students and postdocs in the laboratory about this, I ended up slightly modifying my experimental procedure. This experience taught me the setbacks of research, how to deal with situations like these, how to become a better problem solver, and improved my laboratory skills. 

Working at LBNL gave me the opportunity to meet other people interested in the same field of study as me and learn about their experiences as researchers. This summer, I became more independent and was able to take the responsibility to carry out a research project successfully. I would have never imagined working on a project like this one in my sophomore summer of college independently without a laboratory partner. During my project I was supervised and I always clarified my doubts with my supervisor, however, I made decisions and designed my own experimental procedure parts of the project. I definitely became more confident in myself and my abilities to do well.

Towards the end of my internship, I gave a presentation about my work to my entire laboratory group. I have never been fond of public speaking, but have also never been afraid of it. Before this presentation, I was a decent public speaker, but there was a lot of room for improvement. This internship experience taught me how to prepare a concise and clear presentation as well as how to present well. After practicing the presentation for some time, I was able to work on my presenting skills and I am glad to say I noticed a big improvement in my presentation abilities.

This summer, not only did I improve my academic skills, my confidence, and presentation skills, but I also grew as a person. I became more independent, learned how to handle problems that came up better, became more patient, and, more importantly, I believed more in myself. I really enjoyed my time at the laboratory and would like to thank Cal Energy Corps and the team at LBNL that guided me through this internship.