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CO2R_to_C1_products_manuscript_ACS_final.pdf (1.65 MB)

From Electricity to Fuels: Descriptors for C1 Selectivity in Electrochemical CO2 Reduction

preprint
submitted on 17.12.2019 and posted on 31.12.2019 by Michael Tang, Hongjie Peng, Philomena Schlexer Lamoureux, Michal Bajdich, Frank Abild-Pedersen
Electrochemical reduction of carbon dioxide (CO2) over transition metals follows a complex reaction network. Even for products with a single carbon atom (C1 products), two bifurcated pathways exist: initially between carboxyl (COOH*) and formate (HCOO*) intermediates and the COOH* intermediate is further bifurcated by pathways involving either formyl (CHO*) or COH*. In this study, we combine evidence from the experimental literature with a theoretical analysis of energetics to rationalize that not all steps in the reduction of CO2 are electrochemical. This insight enables us to create a selectivity map for two-electron products (carbon monoxide (CO) and formate) on elemental metal surfaces using only the CO and OH binding energies as descriptors. In the further reduction of CO*, we find that CHO* is formed through a chemical step only whereas COH* follows from an electrochemical step. Notably on Cu(100), the COH pathway becomes dominant at an applied potential lower than −0.5V vs. RHE. For the elemental metals selective towards CO formation, the variation of the CO binding energy is sufficient to further subdivide the map into domains that predominantly form H2, CO, and ultimately more reduced products. We find Cu to be the only elemental metal capable of reducing CO2 to products beyond 2evia the proposed COH pathway and we identify atomic carbon as the key component leading to the production of methane. Our analysis also rationalizes experimentally observed differences in products between thermal and electrochemical reduction of CO2 on Cu.

Funding

Energy Innovation Hub Renewal - Fuels from Sunlight

Basic Energy Sciences

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History

Email Address of Submitting Author

hjpeng@stanford.edu

Institution

SUNCAT Center for Interface Science and Catalysis

Country

United States

ORCID For Submitting Author

0000-0002-4183-703X

Declaration of Conflict of Interest

No conflict of interest

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in Applied Catalysis B: Environmental

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