Zinc oxide-modified glass-coated tin-doped indium oxide electrode for the electrocatalytic reduction of hydrogen peroxide in neutral media

This study investigates the electrodeposition of nanostructured zinc oxide (ZnO) films on indium tin oxide (ITO)-coated glass substrates to develop an electrocatalytic sensor for hydrogen peroxide (H₂O₂) detection in neutral media. Optimal deposition conditions, −1.0 V versus SCE (saturated calomel electrode) for 10 min, produced ZnO/ITO glass electrodes with the highest H₂O₂ reduction activity. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses confirmed the formation of homogeneous, well-adhered wurtzite-structured ZnO films on the ITO substrate.

The performance of the modified electrode was strongly influenced by phosphate buffer solution (PBS), with 0.1 M at pH 7 providing the optimal response. Electrochemical tests demonstrated a linear response for H₂O₂ concentrations ranging from 0.0625 to 5.00 mM (R² = 0.9988), with a sensitivity of 44.7 μA·mM⁻¹·cm⁻² and a detection limit (LOD) of 14.8 μM.

Kinetic studies revealed an electron transfer coefficient (α) of 0.711 and a diffusion coefficient (D) of 3.8 × 10⁻⁷ cm²·s⁻¹. The sensor retained >95 % of its initial current, showed excellent selectivity against ascorbic acid, glucose, uric acid, and nitrite, and accurately detected H₂O₂ in tap water and pharmaceutical samples. These findings position the ZnO/ITO glass platform as a cost-effective, reliable, and scalable solution for in situ H₂O₂ monitoring in water treatment and other neutral aqueous applications.