A new ligand, namely, 2-(5-(pyren-1-yl)pentyl)-9-methyl-1,10-phenanthroline,
as well as new bis(2,9-dialkyl-1,10-phenanthroline)copper(II) complexes
were designed, which were immobilized on multiwalled carbon nanotube
(MWCNT) electrodes. These complexes show a high tendency of autoreduction
into their copper(I) form according to electrochemical and EPR experiments.
These complexes exhibit strong interactions with MWCNT sidewalls either
with or without anchor functions such as the pyrene moiety. The pyrene-modified
derivative can be electropolymerized on glassy carbon and MWCNT electrodes
to form a poly-[bis(2-(5-(pyren-1-yl)pentyl)-9-methyl-1,10-phenanthroline)copper(II)]
metallopolymer film. Furthermore, these MWCNT-supported bis(2,9-dialkyl-1,10-phenanthroline)copper
complexes demonstrate a low overpotential for a 4H+/4e– oxygen reduction reaction at pH 5 with an onset potential
of 0.86 V versus RHE. Integration of these functionalized MWCNTs at
gas-diffusion electrodes of H2/air fuel cells led to a
high open-circuit voltage of 0.84 V and a maximum current density
of 1.77 mW cm–2 using a Pt/C anode.