Proton transfer dynamics dictate quinone speciation at lipid-modified electrodes

Proton-coupled electron transfer (PCET) reactions are ubiquitous in biochemistry and alternative energy schemes. Natural enzymes utilize quinones in proton transfer chains and energy conversion processes. Here, we utilize a bio-inspired hybrid bilayer membrane system to control the reaction mechanism of a quinone molecule covalently bound to an electrode surface. In particular, by impeding proton access to the quinone moiety, we change the reaction pathway from a PCET process to a pure electron transfer step. We further alter the reaction pathway to a stepwise PCET process by controlling the proton flux through the use of an alkyl proton carrier incorporated in the lipid membrane. By modulating proton availability, we control the quinone reaction pathway without changing the molecular structure of the redox species. This work provides unique insight into PCET reactions and a novel electrochemical platform for interrogating them.