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Hydrogen Peroxide Detection Using Biogenic and Synthetic MnO 2

Hydrogen Peroxide Detection Using Biogenic and Synthetic MnO 2. Shu Feng, Jim Nurmi, Paul Tratynek Satya Chinni, Brad Tebo Department of Environmental and Biomolecular Systems OGI School of Science and Engineering Oregon Health & Science University. H 2 O 2 Detection with MnO 2 Electrodes.

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Hydrogen Peroxide Detection Using Biogenic and Synthetic MnO 2

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  1. Hydrogen Peroxide Detection Using Biogenic and Synthetic MnO2 Shu Feng, Jim Nurmi, Paul Tratynek Satya Chinni, Brad Tebo Department of Environmental and Biomolecular Systems OGI School of Science and EngineeringOregon Health & Science University

  2. H2O2 Detection with MnO2 Electrodes • Cyclic Voltammetry (CV) • Voltage is applied across a working electrode and a counter electrode, scanning between 0 and 1.2 V. • When oxidation or reduction occurs, the current increases, causing a peak. • With cyclic voltammetry using a MnO2 electrode, H2O2 is oxidized at ~0.7 V, creating a current peak when H2O2 is present. 2H2O2  O2 + 2H2O

  3. H2O2 Detection with MnO2 Electrodes • Chronoamperometry (CA) • In chronoamperometry, voltage is held constant and current is recorded. • Since in the CV the current peak caused by H2O2 occurred around 0.7 V, the voltage is held at 0.7 V and H2O2 is added at regular intervals. • Plateau height of current is linear to concentration of H2O2 in cell.

  4. Electrode Designs Background signal of gold electrode • Gold Micron-Cavity Powder Disk Electrode • Difficult to make sure MnO2 powder is well packed • Background signal of the gold is much higher than the signal with MnO2 packed Signal of MnO2 • Wax-Impregnated Graphite Electrode • Difficult to control amount ofMnO2 on electrode, as well as to control uniformity of powder on the surface Peak from H2O2 No H2O2 present

  5. Electrode Designs Electrode Head Spin Coating Apparatus • Glassy Carbon Electrode with Spin Coated MnO2 • Excess MnO2 solution is pipetted onto the electrode surface. • By controlling spin speed, an even coat can be achieved. • However, after a long period of time in solution, MnO2 eventually falls off. Close-up views of the electrode surface Uneven MnO2 surface after time in solution

  6. Electrode Validation • Standard Curve • Addition of H2O2 consistently displays linearity with current plateau height. • However, behavior of electrode changes over time and length of exposure to H2O2.

  7. Electrode Validation • Standard Additions • A sample of unknown concentration is injected into solution and CA is run. • Volumes of a standard concentration are injected to create a calibration curve that can be used to solve for concentration of the unknown.

  8. Conclusions • Gold micron-cavity powder disk electrode has a high background signal from gold. • Amount of MnO2 is difficult to control for on the wax impregnated graphite electrode. • Spin coated carbon electrode produces a evenly coated electrode, but produces a varied response. • Standard addition allows these electrodes to be used as a sensor. • Biogenic and synthetic MnO2 electrodes both have H2O2 sensing capabilities, but the differences between them need to be further studied.

  9. Goals For Next Summer’s Intern…(or me in the next week) • Determine effects of aging of the electrode and MnO2 powder • Further characterize electrode behavior in different electrolyte conditions (pH, concentration, etc) • More biogenic vs. synthetic MnO2 comparison • Resolve problems with using sensor in seawater Acknowledgments Jim Nurmi Paul Tratynek Satya Chinni Brad Tebo Vanessa Green EBS Department

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