Anode Preparation Strategies for the Electrocatalytic Oxidation of Water Based on Strong Interactions between Multiwalled Carbon Nanotubes and Cationic Acetylammonium Pyrene Moieties in Aqueous Solutions.

A strategy is reported for the immobilization of iridium-based water oxidation catalyst 3 onto fluorine-doped tin oxide (FTO) anodes evaluated for the electrocatalytic oxidation of H2 O. The strategy is based on noncovalent π-π interactions between multiwalled carbon nanotubes (MWCNTs) and the cationic acetylammonium pyrene moiety (Pyr+ ) covalently attached to a NHC IrCp*Cl2 catalytically active center (NHC=N-heterocyclic carbene, Cp*=C5 Me5 ). The dispersive properties of the Pyr+ moiety in compound 3 leads to the formation of stable MWCNT dispersions in aqueous solutions. In addition, the MWCNT/3 assembly shows activity in the Ce4+ -driven oxidation of H2 O. FTO/MWCNT/3 anodes show increased current densities when used as a working electrode for the electrocatalytic oxidation of H2 O. At higher anodic polarizations initially high current densities were achieved; however, these currents prove to be non-sustained due to delamination and degradation of the catalytically active surface. The immobilization strategy is limited to applications below 1.4 V vs normal hydrogen electrode (NHE) as oxidation of the pyrene backbone is evident at higher potentials.