Chemistry is like a puzzle, where the right equations, laws, and, of course, exceptions to those laws must fit in order to put the pieces together. Solving these puzzles fascinated Samantha Johnson in high school and inspired her to pursue a career in science. She is now a postdoctoral fellow with the Center for Molecular Electrocatalysis (CME) Energy Frontier Research Center (EFRC).
Growing up in the rural High Five Plains of eastern Colorado catalyzed her interest in alternative energy. At the time, corn ethanol was rapidly gaining momentum in the region, and she was interested in biological approaches to processing lignin, a plant cell wall component that is tough to break during biofuel production. She worked in the lab of Alan Weimer at the University of Colorado (CU) studying the process of depositing nanometer-thick films for electronics fabrication using atomic layer deposition while pursuing a bachelor’s in chemical engineering. Her knack for taking an engineering approach to solving chemistry problems led her to find a connection between her engineering studies and design of inorganic, metal-based molecular catalysts. Molecular catalysts are complexes that make chemical reactions happen faster and are often designed around a metal center with molecules attached to the metal atom called ligands.
“There was something about metals that I felt like I had a feel for,” Johnson mused.
In graduate school, she worked for William A. Goddard in Materials Science at the California Institute of Technology in Pasadena as a theoretical chemist. She worked on mechanisms for small molecule activation. It was the relationships she nurtured during her undergraduate studies that got her through some of the challenges of graduate school. “I think the best advice I got was from Charles Musgrave at CU, which was -- you can spend a lot of time comparing yourself, and that’s just time that takes away from doing good work.”
What was supposed to be an “easy” summer kinetics project ended up challenging a long-held belief about ligand participation in hydrogen production using rhodium, a transition metal, Cp* bipyridine catalyst. There are non-innocent ligands that give the metal centers a helping hand to speed up the reaction and innocent ligands, which do not participate in the reaction. Cp*, one such innocent ligand, is a pentagon-shaped molecule with five methyl groups arranged around it like a star. All of the chemistry was thought to be at the metal center. However, with a weak acid, Cp* hosts a proton. From this proton, hydrogen is produced by introducing a stronger acid. “It turned out to be more exciting than we thought,” Johnson said.
Working on this project, she had what she describes as a bit of an ostrich moment, where she realized that she needed to stick her head out of her lab and start talking with her fellow colleagues about her work. This really helped her to find the answers she had been looking for. “You don’t know what you don’t know if you don’t talk to people,” she said.
She moved to a postdoctoral fellow position at CME to tackle catalytic design on a larger scale. The focus of CME is to design catalysts that convert electrical energy into fuel or to convert chemical energy into electrical energy. When electrons flow, they produce energy in the form of electricity, but this energy is difficult and costly to store. Movement of protons also accompanies this electron flow, and scientists at CME are trying to understand the behavior of these electrons and protons to make hydrogen reactions faster, design catalysts to split oxygen, and improve catalysts that can turn nitrogen to ammonia, which is a chemical form of fertilizer used to feed plants. These are all reactions that are important for energy production, because they can be used to store or produce energy.
At CME, Samantha really enjoys the collaborative spirit that is fostered by working as a part of an EFRC. One of the many projects she works on involves screening catalysts to be synthesized and tested in the lab. “One of the nice things about CME is that we have experimental counterparts literally in the next building over,” Johnson said. The power of coupling theory and experiment enables her to work in an iterative process where continuous feedback between the two enables the work to flourish.
“The best science happens among friends, so that’s been really nice here,” she said. “I think the fact that we all work on different aspects of a similar goal really gives you a chance to attack a project from different angles.”
When she is not in the lab, Johnson likes to give back to her community by participating in career days at local schools. Growing up, she wanted to be a journalist, because -- as a self-described nerd -- she watched the news show Meet the Press, read Newsweek, and had exposure to the daily role of journalists. She wants to show kids that the daily routine of a scientist is not confined to a bench, but that reading, writing, and collaboration with your peers play huge roles in scientific discovery.
For Johnson, having passion for what she does and experiencing the joy of discovery has driven her to succeed early in her career. She hopes to share this passion with others as she prepares to embark on the next phase of her scientific career.
