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

31 December 2019, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


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.


CO2 reduction
density functional theory
reaction mechanisms


Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.