Biomimetic versus enzymatic high-potential electrocatalytic reduction of hydrogen peroxide on a functionalized carbon nanotube electrode

We report the non-covalent functionalization of a multi-walled carbon nanotube (MWCNT) electrode with a biomimetic model of the horseradish peroxidase (HRP) active site. By modifying the MWCNT electrode surface with imidazole-modified polypyrrole, a new biomimetic complex of HRP was synthesized on the MWCNT sidewalls via the coordination of imidazole (Im) to the metal centre of iron protoporphyrin IX, affording (Im)(PP)Fe(III) . Compared to the pi-stacking of non-coordinated (PP)Fe(III) on a MWCNT electrode, the (Im)(PP)Fe(III) -modified MWCNT electrode exhibits higher electrocatalytic activity with an I (max) = 0.52 mA cm(–2) for the reduction of H(2)O(2), accompanied by a high onset potential of 0.43 V vs. Ag/AgCl. The performances of these novel surface-confined HRP mimics were compared to those of a MWCNT electrode modified by HRP. Although the enzyme electrode displays a higher electrocatalytic activity towards H(2)O(2) reduction, the (Im)(PP)Fe(III) -modified MWCNT electrode exhibits a markedly higher operational stability, retaining 63% of its initial activity after one month.