Enhancement of H₂O₂ current at electrodes made of Fenton-Activated carbon nanotubes

Multiwalled carbon nanotubes (CNT) were activated toward the oxidation and reduction of hydrogen peroxide (H2O2) by soaking them in the Fenton reagent (H2O2 + Fe(II)) at room temperature for 24 h. Such CNTF24h displayed the sensitivity and limit of H2O2 detection that surpassed those for the original control CNT by similar to 1 order of magnitude. The CNTF24h-based electrodes allowed for the anodic and cathodic determination of H2O2 within a wide linear range of 0.6 - 4500 mu M (R-2, 0.998) and 1.1 - 3000 mu M (R-2, 0.996) at 0.45 and -0.20 V, respectively, which placed them above most H2O2 sensors prepared by far more elaborate protocols. Such electrodes also provided a good accuracy and precision of H2O2 detection (96-102 % recovery, RSD < 4 %) at -0.20 V in a variety of real-life samples with a short response time t(90%) = 4.0 +/- 0.5 s. The stability of H2O2 current was 70 % better at a CNTF24h electrode than at a platinum one in a 3-h long continuous amperometric experiment. The Raman and XPS analyses indicated that the Fenton treatment increased the content of oxidized defects on the surface of CNT, which correlated with the enhancement of H2O2 current. One can hypothesize that such oxidized defects acted as electrocatalysts or redox mediators for the oxidation and reduction of H2O2. The Fenton-activated CNT represent an attractive electrode material for the development of electroanalytical sensors.