Positive Electrochemical Potentials Induce Enhanced Chemoselectivity and Activity in the Thermocatalytic Hydrogenation of 3-Nitrostyrene.

Electrochemical promotion of catalysis is emerging as a powerful approach to control chemical reactions externally without complex catalyst modification, but this has mostly been used for substrates with a single reactive group so far. Herein, we demonstrate that this approach can induce full chemoselectivity in catalytic transformations of substrates with multiple functional groups. Specifically, we show that application of a positive electrochemical potential during the thermocatalytic hydrogenation (TCH) of 3-nitrostyrene exclusively delivered one single product, 1-ethyl-3-nitrobenzene, with six-fold enhanced yield, while a complex product mixture was obtained at open circuit voltage. These effects resulted from the combined effects of a positive electrode polarization and acidification of the bulk solution through a concurrent hydrogen oxidation reaction (HOR). Surface-enhanced infrared absorption spectroscopy and kinetic experiments showed that the positive polarization optimized the surface concentrations of reactants and the adsorption properties of 3-nitrostyrene and hydrogenation products. Validation with additional reactants and catalyst implies a possible broader relevance of our findings beyond the initial system of 3-nitrostyrene hydrogenation. Overall, our work provides fundamental insight into the effects of electrode polarization on thermal hydrogenation reactions and opens new opportunities to use electrochemical promotion to control chemoselectivity and activity.