Electrically-Driven Proton Transfer Promotes Brønsted Acid Catalysis by Orders of Magnitude

Electric fields play a key role in enzymatic catalysis and can enhance reaction rates by 100,000-fold, but the same rate enhancements have yet to be achieved in thermochemical heterogeneous catalysis. Herein, we probe the influence of catalyst potential and interfacial electric fields on heterogeneous Brønsted acid catalysis. We observe that variations in applied potential of ~360 mV lead to a ~100,000-fold rate enhancement for 1-methylcyclopentanol dehydration catalyzed by carbon-supported phosphotungstic acid. Mechanistic studies support a model in which the interfacial electrostatic potential drop drives quasi-equilibrated proton transfer to the adsorbed substrate prior to rate-limiting C-O bond cleavage. Large increases in rate with potential are also observed for the same reaction catalyzed by Ti/TiOyHx and for the Friedel Crafts acylation of anisole with acetic anhydride by carbon-supported phosphotungstic acid. This work highlights the important role interfacial electrochemical potential can play in Brønsted acid catalysis.