Fig xA Polarization curves for HPRR on a rotating

3.3. Hydrogen peroxide reduction and Cy3 NHS ester on Pd(poly)
Since hydrogen peroxide might appear either as a reaction intermediate during 4e-series pathway for ORR or as the reaction product during 2e- pathway, the separate measurements of HPRR/HPOR are also performed in oxygen free 0.1 M HClO4 and 0.1 M NaOH solutions, both containing 5 mM H2O2. Recorded polarization curves are compared with the corresponding ones for ORR.
Polarization curves recorded in both anodic and cathodic directions for hydrogen peroxide reduction/oxidation on Pd(poly) electrode in acid and alkaline solutions are shown in Fig. 5. Initial potentials for hydrogen peroxide reduction on Pd(poly) in 0.1 M HClO4 solution are 0.58 V in anodic direction, and 0.55 V in cathodic direction, Fig. 5a. In our previous work, similar values of the initial potential for HPRR were obtained on gold supported Pd nanoislands in 0.1 M HClO4 solution [28]. In 0.1 M NaOH solution the initial potentials for HPRR are -0.06 V and -0.11 V in anodic and cathodic direction, respectively, Fig. 5b.