The high CO2 emissions from processing of fossil fuels for energy generation are a major contemporary challenge. The chemical transformation of CO2 to high-energy molecules is an avenue to alleviate this problem, and, therefore, the electrochemical reduction of CO2 has attracted wide interest. Electrochemical reduction of CO2 using high temperature solid oxide electrolysis cells (SOECs) to produce CO has been considered a viable approach, since CO represents a valuable intermediate to the production of synthetic fuels using established processes, such as Fischer-Tropsch. While promising, SOECs suffer from high overpotential losses induced by the limited ability of the cathode electrocatalyst (traditionally, Ni) to electrochemically reduce CO2. Ni is preferred over other metals, since it is fairly inexpensive and has comparable thermal compatibility with the other cell components. In the present work, we employ density functional theory (DFT) calculations combined with microkinetic modeling to determine the critical steps that govern electrochemical reduction CO2 on Ni catalysts. Based on this understanding, DFT calculations are used to screen for Ni alloys that can improve the energetics associated with this process. A “volcano”-type relationship between the calculated electrochemical rates for reduction of CO2 and the binding energy of oxygen on Ni and Ni alloys is found, suggesting that the binding energy of oxygen can be used as a descriptor for the activity of Ni alloys toward electrochemical reduction of CO2. Controlled experimental studies with SOECs and thorough characterization of the electrocatalysts are used to support the DFT predictions.

Design of Ni-based electrocatalysts for CO2 electrolysis from first-principles

253rd National Meeting (2017)

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