Hydrogen-Atom Binding Energy of Structurally Well-defined Cerium Oxide Nodes at the Metal−Organic Framework-Liquid Interfaces

12 April 2024, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Redox-active metal oxides are prevalent in the fields of thermal, photo-, and electrocatalysis. Thermodynamics of proton-coupled electron transfer (PCET) reactions at their surfaces are critical as they scale with their activity as a catalyst. The structural heterogeneity and ambiguity of surface sites have largely precluded structural understanding of the exact redox-active sites, challenging chemists to design the catalyst structure down to the atomic level. Here, we report electrochemically determined stoichiometry and thermodynamics of PCET reactions of the cerium-based metal−organic framework (MOF), Ce-MOF-808. Cyclic voltammograms (CVs) of the MOF-deposited electrodes in aqueous buffers at various pHs revealed a Faradaic couple that can be ascribed to Ce4+/3+ redox. Plotting the half-wave potential (E½) against the electrolyte pH resulted in a Pourbaix diagram with a slope of 65 ± 9 mV/pH, suggesting a 1H+/1e- stoichiometry. Using the thermochemical analogy between 1H+/1e- and one H-atom (H∙), the H-atom binding energy on the hexanuclear Ce6 node, the Ce3+O−H bond dissociation free energy (BDFE), was calculated to be 77 ± 2 kcal mol-1. In-silico calculations quantitatively corroborated our BDFE measurements. Furthermore, multiple proton topologies were computationally elucidated to exhibit similar BDFEs to the experimental values, agreeing with the wide Faradaic features of all CVs, implicating that the system has a substantial BDFE distribution. To the best of our understanding, this is the first thermochemical measurement of H-atom binding on MOFs. Implications of the presented thermochemical measurements on catalysis using metal oxides and MOFs are discussed.


Metal-Organic Frameworks
Proton-Coupled Electron Transfer
Renewable Energy

Supplementary materials

Supporting Information
Physical characterization including N2 adsorption-desorption isotherm, SEM images, PXRD patterns, detailed analysis of CVs, and details on computational characterization.


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.