Functionalizing Carbon Nanotubes with Bis(2,9-dialkyl-1,10-phenanthroline)copper(II) Complexes for the Oxygen Reduction Reaction

Abstract

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.