Electrochemical\nPromotion of Catalysis by Lithium-Ion

Electrochemical promotion of catalysis\n(EPOC) or non-Faradaic\nelectrochemical\nmodification of catalytic activity (NEMCA) is a general phenomenon\nin heterogeneous catalysis that in situ controls reaction rates of\nthermal catalysts via the application of electrical potential and\nenables supply/removal of ionic species (promoters) from the electrolyte.\nIn this work, we investigated electrochemical promotion by Li-ion\nfor carbon monoxide oxidation and reverse water gas shift (RWGS) reactions.\nNanostructured Pt films (50 and 100 nm thickness) and highly dispersed\nFeO<sub><i>x</i></sub> nanowires (<i>d</i> = 10\nnm) were deposited on the lithium lanthanum titanate (Li<sub>0.29</sub>La<sub>0.57</sub>TiO<sub>3</sub>, LLTO) solid electrolyte. By applying\nconstant electrical potential/current, the catalytic reaction rates\nfor both CO oxidation and RWGS were modified in a non-Faradaic way\ndue to Li-ion migration to/from Pt and FeO<sub><i>x</i></sub> catalysts, as evidenced by STEM, XRD, and XPS. For CO oxidation,\nthe reaction rate over FeO<sub><i>x</i></sub> decreased\npermanently under positive polarization, returning to the initial\nstate only under negative polarization. Pt films showed similar rate\ndecreases upon positive polarization but experienced an immediate\nincrease after returning to the open circuit. For RWGS, positive polarization\nover FeO<sub><i>x</i></sub> led to permanent electrochemical\npromotion with the rate increasing in the H<sub>2</sub>-rich environment\nand decreasing under CO<sub>2</sub>-rich conditions. Pt catalysts\nshowed rate increases under all conditions. These differences suggested\nthat FeO<sub><i>x</i></sub> reacted with Li-ion in the presence\nof electrons due to its redox activity, while Pt remained chemically\nstable and did not exhibit similar interactions. Cyclic voltammetry\n(CV) provided insights into the interaction of Li<sup>+</sup> with\nthe catalyst and its influence on electrochemical reactions.