By: David Velazquez
Hey everybody! I’m David Velazquez and I’m currently a second-year graduate student at the University of Southern California. I am in the chemistry program with an emphasis on catalysis in the Marinescu group. With the start of the fall semester coming soon, I would like to share my summer experiences with all of you.
I had the pleasure of mentoring Crystal Mendoza, a sophomore REU student from Kalamazoo College. We came in early every day and had a nice small conversation about life before we began our experiments. It was great to have someone help with my project; reducing carbon dioxide (CO2) by catalysis. The abundance of this greenhouse gas is increasing every year due to energy demands and causes harmful environmental effects such as global warming, wildfires, ice melting, and ocean acidification that causes coral bleaching. The problem is that our major energy sources are nonrenewable and produce a lot of CO2. Currently, renewable resources have not been able to replace fossil fuels completely. Another issue is that there is a storage problem with renewable energy and in the Marinescu group we try to solve all these issues with catalysis. With a proper electrocatalyst we can store renewable energy by converting small abundant molecules like CO2 and H2O into syngas. This allows us to effectively recycle the CO2 in the air.
Our project is on cobalt 2-phosphinobenzenethiolate catalyst (CoPS). Using other acids instead of water (Figure 2) also produced compositions of syngas; however, these favored production of H2 over CO. Part of the goal this summer was finding ways to optimize this conversion by changing experimental conditions and understanding the mechanism. This summer involved synthesis of CoPS which turned out to be more difficult than we thought! Part of the struggle is the chemistry must be done in inert conditions, so preparation of the glassware and chemicals was key. We set out to find experimental support for our proposed catalytic cycle. Chemists typically do this is by studying the elementary steps in a reaction which involves characterization of chemical intermediates or short-lived species. Electrochemical studies showed that CoPS gets reduced by an electron before it can bond with CO2 or a proton. We were able to characterize the reduced complex by UV-Vis, X-ray crystallography, elemental analysis, and 1H-NMR. We repeated this studies with our catalyst bonded to CO right before it is released as a product. We did FT-IR studies, UV-Vis, 1H-NMR, and cyclic voltammetry to characterize these intermediates.
Although we were able to accomplish most of our summer goals, it was not without struggle. A lot of the intermediates we make are not long lived, so keeping them stable enough to analyze is a challenge! Most of these catalysts must be kept inside an inert gas glovebox and be analyzed quickly. Studying a mechanism feels like you are a detective trying to figure out all the clues which ultimately reveal the answer, although it can be frustrating at times, when that eureka moment hits, it makes it all worth it.
I learned a lot about my project this summer. It has been great being able to do research on a project that is solving issues of sustainability and pollution by chemistry. Special thanks to Dr. Smaranda Marinescu, Dr. Jessica Dutton, the Wrigley Institute and all those who supported me this summer!