Congratulations to Rebecca Hamlyn, a Chemical Sciences Division postdoc stationed at the ALS! The Department of Energy Hydrogen and Fuel Cell Technologies Office has recognized Hamlyn for her project: Approaching the Complex Composite Electrode Interface with operando AP-XPS.
In her own words:
I was first inspired to get into this field to address issues of climate instability and the role that chemistry plays in this. A majority of the issues that we currently face in the relationship between energy and the environment come down to chemistry. Likewise, much of the technological solutions to our clean energy needs will involve chemistry for decarbonization, fuels, and storage. The synthesis of clean hydrogen is a part of this roadmap to a sustainable energy sector, as it already is a major chemical feedstock, but will also grow to serve as a clean liquid fuel and be useful as a renewable energy storage medium to expand and stabilize the grid.
The H2New consortium in the DOE funds most of my research and is tasked with the scale up of electrolyzers, which are used to split water into hydrogen and oxygen using electricity. I study how the electrode works to split the water molecule and form oxygen, which is the kinetic barrier for the process. The components involved are the most expensive part of an electrolyzer stack. The materials that comprise the electrode are complex heterostructures, made of catalyst nanoparticles, material supports, polymer electrolytes, and of course, water. To understand how these complex structures work, we are using operando spectroscopy to study how the different components function and change while the electrolyzer is running. In this way, we aim to provide key insight that can be used for the design of new material systems that are more efficient, more durable, and which may not rely so much on rare, expensive metals.
Historically, x-ray photoelectron spectroscopy (XPS) was a very fundamental, ultra-high-vacuum technique. Decades of technological advancement has pushed its widespread use into the ambient pressure regime (mTorr), where we can study solid-gas interactions. Beamline 9.3.1 at the ALS has advanced this pressure regime even further, up to tens of Torr, where we can achieve a meaningful liquid layer on the front of our electrodes to study electrochemistry while reactions are taking place. The state-of-the-art system of study when I arrived was an experiment known as the “dip and pull technique,” involving thin layers of liquid pulled onto flat thin film surfaces.
My work has been to develop an operando electrochemical cell where we can take fully composite membrane-bound materials that are used in large-scale stack testing and directly load into our chamber for study. Because the materials are a composite, some parts are susceptible to rapid beam damage, and we have found that not only can this ruin our signal of interest, but can cause the development of species that may lead to erroneous data interpretation. We had to upgrade our cell design and develop a sub-second data acquisition mode called “snapshot mode” to be able to take rapid scans of our material while moving across the surface. This results in avoidance of almost all damage from the beam and data that is more representative of the complex surface. I have identified stark differences between some commercial catalysts that are candidates for scale up in electrolyzer devices, as well as identification of oxide signatures affiliated with high water splitting/oxygen evolution. More detailed findings are to come, as I am still processing much of the data we have collected.
There are so many experiments and different materials systems yet to explore. Many beam-sensitive polymers are now viable candidates for study. In the operando cell, we have started some CO2 reduction experiments. And further, we are just on the cusp of being able to do real time-resolved measurements using this snapshot mode, which may yield important mechanistic information about chemical processes at play.