Electrochemistry of Methyl Viologen and Anthraquinonedisulfonate at Diamond and Diamond Powder Electrodes: The Influence of Surface Chemistry

The electrochemical behaviour of methyl viologen and anthraquinonedisulfonate was studied at electrodes produced from differing forms of diamond, including microcrystalline boron doped diamond, boron doped diamond powder and detonation nanodiamond powder. Two types of electrode pretreatment were employed to produce two dissimilar surface terminations: hydrophobic H-terminated and hydrophilic O-terminated. In the case of methyl viologen, it was found that the reduced neutral molecule adsorbed on all three electrodes if they were hydrogen terminated, but not if they were oxygen terminated. For anthraquinonedisulfonate, no adsorption was found on the solid diamond electrode, although again significant adsorption was noted on the powder electrodes, provided they were hydrogen terminated. The reasons underlying these observations are discussed in terms of hydrophobic and electrostatic interactions and the electrode morphology. The work provides information into the likely occurrence of adsorption and concomitant electrode fouling, which may be experienced in electroanalytical applications using solid and powdered forms of diamond.