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Density Functional Theory Studies of CO2 Electrochemical Reduction on Copper Catalysts

Research Scholar

Xiaowa Nie, Chemical and Biomolecular Engineering (China)
Monica R. Esopi, Co-Researcher
Michael Janik, Co-Researcher
Aravind Asthagiri, Faculty Mentor

Biography

Xiaowa Nie is a postdoctoral researcher in the Department of Chemical and Biomolecular Engineering at The Ohio State University. She earned her PhD degree at Dalian University of Technology in China, and she was a co-supervised PhD student in the International Joint Center for Energy Research established by Penn State University and Dalian University of Technology. She specializes in computational catalysis research including biomass conversion mechanism, zeolitic shape-selective catalysis for synthesis of organic chemicals, acidic ionic liquid catalysis for organic reactions, metal and metal oxide catalysis and CO2 conversion mechanism. Nie has published nine peer-reviewed journal papers and participated in several international conferences.

What is the issue or problem addressed in your research?

Electrochemical reduction of carbon dioxide (CO2) is a candidate for energy storage and synthetic fuel production, and may allow for a synthetic carbon cycle using liquid fuels. Such an advance would allow society to maintain its current transportation structure in a carbon neutral manner. Cu electrocatalysts uniquely reduce CO2 to hydrocarbon products under reasonable current density and efficiency, nevertheless, high overpotentials and poor understanding of the factors that affect the product selectivity of Cu catalysts are significant barriers to the application of CO2 electrocatalytic reduction to produce hydrocarbon fuels.

What methodology did you use in your research?

We use density functional theory (DFT), an accurate quantum mechanics method, to model CO2 electroreduction on the Cu(111) surface. In the past, this type of modeling work has evaluated the relative free energies of intermediates along reaction paths, but we have undertaken the first systematic study that evaluates the activation barriers for the elementary steps, which are critical to determining the dominant paths to methane and ethylene production during CO2 electroreduction on Cu.

The current calculations show that methane production on Cu occurs through the reduction of carbon monoxide (CO) to a hydroxymethylidyne (COH) intermediate, followed by further reduction to C, and subsequent protonation steps to CH, CH2, CH3, and finally methane. The presence of surface carbene species Cu=CH2 allows for ethylene production from the same path as methane. The reaction paths based on our DFT results are supported by available experimental electrokinetic data, and represent the most convincing routes associated with CO2 or CO electroreduction on Cu electrodes to date.

What are the purpose/rationale and implications of your research?

These modeling results provide insights on key steps that should be targeted for both the selectivity towards the desired product, and for reducing the overpotential for CO2 reduction. Future work will explore the effect of changing the local structure of the catalyst on the barriers for these key steps. Our modeling work provides fundamental insight into bottlenecks in CO2 electroreduction surface chemistry, which can be used to screen for improved catalysts for this process.