Hydrogen Peroxide Detection Using Biogenic and Synthetic

MnO2Shu Feng, Jim Nurmi, Paul Tratynek

Satya Chinni, Brad TeboDepartment of Environmental and Biomolecular Systems

OGI School of Science and EngineeringOregon Health & Science University

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

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.

Electrode Designs

• 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

• Wax-Impregnated Graphite Electrode– Difficult to control

amount of MnO2 on electrode, as well as to control uniformity of powder on the surface

Background signal of gold

electrode

Signal of MnO2

Peak from H2O2

No H2O2 present

Electrode Designs

• 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.

Electrode Head

Spin Coating Apparatus

Close-up views of the electrode surface

Uneven MnO2 surface after

time in solution

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.

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.

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.

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 seawaterAcknowledgments

Jim Nurmi

Paul Tratynek

Satya Chinni

Brad Tebo

Vanessa Green

EBS Department