Comparative Proton Coupled Electron Transfer at Glassy Carbon and Boron‐Doped Diamond Electrodes

Abstract

Abstract The surface modification of carbon electrodes is an area of great interest in both fundamental and applied electrochemistry. Herein we demonstrate a reliable route for the modification of sp3 boron‐doped diamond electrodes through a diazonium reduction and subsequent solid phase synthesis to produce a stable, immobilised layer of surface‐bound anthraquinone. The electron transfer kinetics, surface coverage, and pKa of the immobilised anthraquinone were investigated and compared to those of anthraquinone immobilised via an identical synthetic route onto a glassy carbon sp2 interface. The pKa of anthraquinone was found to be 9.1 on glassy carbon but 6.6 on boron‐doped diamond. Differences in pKa were observed despite the use of identical surface modification strategies and the achievement of comparable surface densities for both types of electrode, and are attributed to the differing dielectric properties of the surface‐modified layers atop either an sp2 or sp3 interface. These results highlight how the underlying substrate can greatly influence the fundamental chemical and electrochemical properties of immobilised molecules, as well as the need for caution when applying well‐established sp2 solid phase synthesis methodologies to sp3 substrates.

Keywords

• Anthraquinone
• Boron-Doped Diamond
• Glassy Carbon
• pKa