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

Abstract

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.