Edge Plane Pyrolytic Graphite Electrode Covalently Modified with 2‐Anthraquinonyl Groups: Theory and Experiment

An edge plane pyrolitic graphite (EPPG) electrode was modified by electrochemical reduction of anthraquinone‐2‐diazonium tetrafluoroborate (AQ2‐N 2 + BF 4 − ), giving an EPPG–AQ2‐modified electrode of a surface coverage below a monolayer. Cyclic voltammograms simulated using Marcus–Hush theory for 2 e − process assuming a uniform surface gave unrealistically low values of reorganisation energies, λ , for both electron transfer steps. Subsequently, two models of surface inhomogeneity based on Marcus–Hush theory were investigated: a distribution of formal potentials, E ′, and a distribution of electron tunneling distances, r 0 . The simulation of cyclic voltammograms involving the distribution of formal potentials showed a better fit than the simulation with the distribution of tunneling distances. Importantly the reorganization energies used for the simulation of E ′ distribution were similar to the literature values for adsorbed species.