Alkali metal cations as promoters of (non) Kolbe electrolysis: a systematic study of their effect on product selectivity Talal Ashraf 2 , Bastian Mei 1,2 , Guido Mul 2 1 Industrial Chemistry Ruhr-University Bochum Universitätsstr, Germany, 2 University of Twente, Netherlands Carboxylic acids in biomass pyrolysis oil can be electrochemically transformed into alkanes and alcohols via Kolbe and Hofer Moest reaction, with selectivity dependent on factors such as electrode material, supporting electrolyte, pH and current densities 1,2 . Alkali metal cations in supporting electrolyte were considered inert spectators for Kolbe electrochemical oxidation 3 . However, our recent studies show that they can affect the oxidation currents and faradaic efficiency. Cations in the electrolyte solution (Li + <Na + <K + ~Cs + ) affect the product profile and electrochemical activity observed in conditions of oxygen evolution reaction (OER), Kolbe electrolysis and Hofer Moest reaction. Small cations interfere more strongly with the surface adsorbed oxygenates. To verify the effect of the cation during the transition from OER to Kolbe reaction, we used a rotating ring disc electrode (RRDE) to identify the inflection zone where OER begins to inhibit and changes in interfacial pH. OER was suppressed at 2.5V RHE with K + cations but not in the presence of Li + cations. References 1. F. J. Holzhäuser, J. B. Mensah and R. Palkovits, Green Chem., 2020, 22, 286–301. 2. C. Stang and F. Harnisch, ChemSusChem, 2016, 9, 50–60. 3. H. J. Schäfer, in Comprehensive Organic Synthesis, eds. B. M. Trost and I. Fleming, Pergamon, Oxford, 1991, pp. 633–658.
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