AUTHOR=Ghuffar Hafsa Abdul , Noh Hyunho 

TITLE=Lithium-coupled electron transfer reactions of nano-confined WOx within Zr-based metal–organic framework

JOURNAL=Frontiers in Chemistry

VOLUME=Volume 12 - 2024

YEAR=2024

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2024.1427536

DOI=10.3389/fchem.2024.1427536

ISSN=2296-2646

ABSTRACT=Interfacial charge transfer reactions involving cations and electrons are fundamental to (photo/electro)catalysis, energy storage, and beyond. Lithium-coupled electron transfer (LCET) at the electrode-electrolyte interfaces of lithium-ion batteries (LIBs) is a preeminent example to highlight the importance of charge transfer in modern-day society. The thermodynamics of LCET reactions define the minimal energy for charge/discharge of LIBs, and yet, these parameters are rarely available in the literature. Here, we demonstrate the successful incorporation of tungsten oxides (WOx) within a chemically stable Zr-based metal-organic framework (MOF), MOF-808. Cyclic voltammograms (CVs) of the composite, WOx@MOF-808, in Li + -containing acetonitrile (MeCN)-based electrolytes showed an irreversible, cathodic Faradaic feature that shifted in a Nernstian fashion with respect to the Li + concentration, i.e., ~59 mV/log([Li + ]). The Nernstian dependence established 1:1 stoichiometry of Li + and e -. Using the standard redox potential of Li +/0 , the apparent free energy of lithiation of WOx@MOF-808 (ΔGapp,Li) was calculated to be -36 ± 1 kcal mol -1 . ΔGapp,Li is an intrinsic parameter of WOx@MOF-808, and thus by deriving the similar reaction free energies of other metal oxides, their direct comparisons can be achieved. Implications of the reported measurements will be further contrasted to proton-coupled electron transfer (PCET) reactions on metal oxides.