TEMPO as a Promising Electrocatalyst for the Electrochemical Oxidation of Hydrogen Peroxide in Bioelectronic Applications

A number of bioelectronic applications work with oxidase enzymes and many of them can operate with small molecule or polymer redox mediators. However, for some oxidases, there are no known redox mediators able to mediate electron transfer. Therefore, electron transfer must occur through peroxide production and oxidation at the electrode surface. Organic redox catalysts such as oxoammonium cations, are able to oxidize H2O2 to form nitroxyl radicals, which can be electro-oxidized and regenerate the oxoammonium cation form. In this study, we investigate the ability to use TEMPO as a platform for the electrocatalytic oxidation of H2O2 at different pHs. The results have shown that TEMPO can be used to monitor H2O2 in broad pH range (≥4) at 530 mV (vs SCE). Combining TEMPO with cholesterol oxidase, we have shown the possibility to monitor the cholesterol oxidation with a linear range between 20 μM and 2.5 mM with a sensitivity of 54.86 mA cm−2 M−1. Furthermore, we have studied the electrocatalytic oxidation of oxalate by oxalate oxidase for biofuel cell applications. These combined results demonstrate TEMPO as a promising electrocatalyst applied for the development of electrochemical biosensors or enzymatic biofuel cells.