SusChEM: Spectro-electrochemical and theoretical study of carbon dioxide up-conversion mechanisms using clathrate hydrates

Brown University, Providence RI

Investigators

Abstract

The Chemical Structure, Dynamics, and Mechanism B Program (CSDMB) of the Chemistry Division supports the project by Professor Christoph Rose-Petruck (PI) and Professor Hannes Jónsson (co-PI). Professors Rose-Petruck and Jónsson are faculty members in the Department of Chemistry at Brown University. The research project focuses on the electrochemical conversion of carbon dioxide (CO2) into useful chemicals. Interest in CO2 conversion has increased significantly in recent years, in response to the increasing demand for sustainable products that are not generated from fossil fuels. While much work is being done to advance these efforts, there are still major hurdles to overcome. One of these is the electro-chemical generation of hydrogen gas that constantly competes with the desired CO2 conversion processes. This competing reaction steals the current (flow of electrons) needed for the CO2 conversion and, in so doing, makes the processes inefficient and costly. To solve this problem, the investigator are conducting the electrochemical conversion of CO2 in snow-like water crystals called clathrate hydrates that can store large amounts of CO2. This "snow" is mixed with salts and water to form an electrically conducting "snow-slush". The use of this mixture for the electro-chemical conversion of CO2 dramatically reduces the competing generation of hydrogen gas, leading to greatly improved yields and reaction efficiency. This discovery has the potential to be transformative in terms of how the conversion of CO2 into value added products is conducted. The use of clathrate hydrates in this fashion is very new, and the reaction mechanisms that enable the success of the approach are unknown. Hence, the researchers are seeking a better understanding of how these reactions work and how they can be manipulated to optimize the yield of a particular desired product. The research activities include a collaborative partnership with the Research Instruments Corporation, a Rhode Island based company. This company is a partner for technology transfer from Brown University into the market place. Recruitment and mentoring of historically underrepresented groups is enhanced through the partnership with the Leadership Alliance. The electrochemical reduction of CO2 into carbonaceous products is carried out in clathrate hydrate-loaded electrolytes. These reaction conditions strongly reduce the needed overpotential and change the product spectrum compared to that obtained with non-clathrate electrolytes. A spectrum of products is produced with low reduction potentials. The researchers hypothesize that reactions inside the clathrate hydrate structures are initiated by hydrogen-radical formation from clathrate water molecules as the clathrate crystals contact the working electrode. The experiments are combined with calculations of the reaction mechanisms and rates. These calculations are based on density functional theory of the electronic structure and minimum energy path calculations to estimate energy barriers for the various reaction steps and rate estimates based on harmonic transition state theory. The research investigates CO2 reduction mechanisms in electrolytes that include clathrate hydrates. The study provides a detailed insight into a new class of reaction mechanisms that use clathrates as water-based frameworks for high energy-efficient up-conversion of CO2 and other molecules. The activities include collaborative partners. The Research Instruments Corporation contributes strength in entrepreneurship and a partner for technology transfer from Brown University into the market place. Recruitment and mentoring of historically underrepresented groups is enhanced through the partnership with the Leadership Alliance.