As a MITEI Energy Scholar, Santosh Singh developed a spectroscopic technique to study subsurface species, like carbon, located beneath metal surfaces, supporting the design of better catalytic materials and functional surfaces for energy production. Singh, a postdoctoral researcher in MIT’s Department of Chemistry, shares how his work solves a fundamental, yet relatively unexplored, challenge at the intersection of chemistry, physics, and materials science.
Q. What are you researching as a MITEI Energy Scholar?
A. My research is focused on understanding fundamental heterogeneous catalytic processes. If the catalyst is a solid material, the reactions sped up by the catalyst occur on the surface; however, species buried below the surface can also impact reactions on the surface. My work seeks to understand how buried atomic species—like carbon, oxygen, or sulfur—can affect the catalytic properties of metal surfaces. The challenge with identifying these buried species is distinguishing them from the same species on the surface without damaging the sample. To illustrate this, let’s consider a painted wooden wall. From the outside, the wall may look perfectly fine, but the wall could be rotten on the inside. To see the hidden damage, you would need to peel the paint away or open up the wall.
In my research, I achieved the equivalent of “seeing inside” the subsurface without damaging the sample. I have developed a vibrational spectroscopic technique that detects subsurface species—in this case, carbon—located beneath the metal surface, which allows us to understand how carbon can diffuse within the metal and ultimately onto the surface where it can impact catalytic reactions.
Q. What impact do you hope this research will have?
A. I’m excited to see how this work can spur other research advancements, especially since this research sits at the intersection of chemistry, physics, and materials science. Answering fundamental scientific challenges can often open new research areas and drive the entire field forward, and I hope this research can play a role in that. It’s like finding a lighthouse in the middle of a dark ocean. Once the light becomes visible, it can help guide new research directions.
We now have methods to detect how carbon diffuses in a metal, and between the surface and subsurface—namely, without damaging the sample and with certainty of its chemical identity. In previous experiments with hydrogen, we revealed that bulk hydrogen behaves very differently from hydrogen on the catalytic surface, and we anticipate bulk carbon atoms will similarly have a unique chemistry compared to carbon on the surface. The evidence behind this hypothesis comes from our observations of graphene formation at low temperatures. We found that carbon atoms buried beneath the surface can move up toward the surface and form graphene at temperatures well below those conventionally required. This is notable because previous methods of integrating graphene in electronic devices required very high temperatures that destroy the intricate circuit structures. Being able to produce graphene at low temperatures could open new possibilities for building improved energy-storage and quantum devices.
Ultimately, most studies are focused on understanding reactions occurring on the surface, but the role of subsurface species is still unexplored. This work addresses a fundamental gap, and hopefully there’s more research to come from this field of study.
Q. What energy transition challenges does this work address?
A. This research is important because it addresses critical energy and material challenges and can aid in the design of better catalytic materials and functional surfaces for advanced energy production. With an understanding of how subsurface carbon atoms diffuse and how they react with oxygen, we can improve the electrodes in direct carbon fuel cells that generate electricity. This could have implications on how we efficiently use carbon sources, like bio waste, to produce clean energy and value-added products at lower temperatures.
We can also apply this research to other subsurface species, like oxygen or sulfur, to better understand the catalytic properties of other metals and advanced materials. The energy sector is currently focused on developing quantum materials and fusion plasma for energy generation. In the production of energy via fusion, a plasma is confined inside the tungsten walls of a tokamak. Before starting the fusion reaction, the walls are cleaned and impurities are removed from the surface, but the impurities in the subsurface of the tungsten walls—which can include carbon, sulfur, and hydrogen—can diffuse towards the surface during the reaction and impact fusion gain. Our research can show us how impurities diffuse under such extreme conditions, enabling the development of materials to improve the efficiency of energy production.
On a broader scale, this research can help develop technologies and processes that maintain industrial efficiency, while reducing impact on the climate. Additionally, as these technologies are brought into society, we should ensure they are accessible and affordable. To do that, it’s essential for there to be contributions from all areas of science and industry. I’m excited for my research to be a part of that.
MITEI’s Energy of the Future series highlights in video and text MIT students working to advance the energy transition and expand energy access.