pH-Dependent response of a hydrogen peroxide sensing probe

• The sensing behavior of a fiber-optic hydrogen peroxide sensor based on Prussian blue/Prussian white redox is investigated.
• The response is examined under a range of pH conditions corresponding to PEM fuel cell operation.
• The optrode remains functional and provides stable and reproducible measurement of H2O2 in the pH range of 2–7.
• The sensor sensitivity increases in lower pH solutions.

The response of a fiber-optic hydrogen peroxide (H2O2) sensing probe is investigated under a range of pH conditions. The H2O2 optrode is prepared by depositing a thin layer of Prussian blue (PB) onto the tip of a multimode optical fiber, and its detection mechanism is based on the PB/Prussian white (PW) redox reaction. PW is oxidized to PB by H2O2 leading to changes in the absorption of visible light. The sensor can be restored after usage by reducing the PB to PW with ascorbic acid. This optrode was previously shown to have good repeatability and sensitivity to H2O2 concentrations at room temperature and a pH of 4. For practical applications, the sensor must be capable of detecting H2O2 in environments spanning a range of pH conditions, including biological and industrial environments which together span pH values from 7 to less than 3. We present experiments using multiple PB optrodes, at pH values ranging from 7 to 2, and for different concentrations of H2O2. The work demonstrates that the optrode remains functional and provides stable and reproducible measurements of H2O2 under a range of pH conditions that correspond, in particular, to those in an operating PEM fuel cell.