Simultaneous electrochemical detection of oxygen (O2) and hydrogen peroxide (H2O2) in neutral media

Abstract

The simultaneous detection of oxygen (O2) and hydrogen peroxide (H2O2) in neutral media was investigated by cyclic voltammetry using a two-working modified glassy carbon (GC) electrode system. Both electrodes were functionalized either by electrodeposited or by chemically-prepared gold nanoparticles (AuNPs). AuNPs electrodeposition was achieved by constant potential electrolysis either at 0.5 or ‐0.5 V/SHE in acidic HAuCl4 solution. Colloidal AuNPs were obtained according four different procedures (type A to D) derived from the classical Turkevich synthesis and further drop-casted on GC. The kinetics of H2O2 oxidation was studied by recording steady-state voltammograms in a deaerated NaCl/NaHCO3 pH 7.4 neutral solution on all the functionalized electrodes and favorably compared to unmodified GC and bare gold electrodes. Both Koutecky-Levich and Tafel treatment of the current-potential curves showed that the highest anodic transfer coefficient αn (0.78 ± 0.14) was obtained with the electrodeposited AuNPs/GC electrode using the most cathodic deposition potential of ‐0.5 V which provided the highest average number of nanoparticles per square micrometer (555 ± 49 µm-2) of very little average size (25 ± 12 nm) NPs. The simultaneous detection and quantification of O2 and H2O2 was achieved only with electrodes functionalized using D-type Turkevich synthesis. In this case H2O2 was detected at the anode while current corresponding to O2 reduction was selectively recorded at a potential close to ‐0.3 V without interference from H2O2.