Fabrication of Nanostructured Pd Thin Films Using Aerosol-Assisted Chemical Vapor Deposition for the Nonenzymatic Electrochemical Detection of H₂O₂

An improved and facile aerosol-assisted chemical vapor deposition (AACVD) process for the production of palladium thin film on indium tin oxide (PdNP-ITO) electrodes was described and applied for the electrochemical detection of hydrogen peroxide (H2O2). The detailed characterization of the films by X-ray diffraction (XRD), scanning electron microscopy/energy-dispersive X-ray (SEM/EDX) spectroscopy, and X-ray photoelectron spectroscopy (XPS) analysis proved the high crystallinity and phase purity of the nanosized metallic palladium films without the evolution of any elemental impurities from the precursor compound. The as-prepared electrodes were used for nonenzymatic amperometric H2O2 detection via electrochemical reduction. The LOD was 40.8 nM with a high sensitivity of 760.84 μA/(μM cm2). From the experimental scan rate variation analysis, the reduction of H2O2 on the PdNP-ITO electrode surface was determined to be adsorption controlled. For this process of adsorption, we calculated the number of electrons involved during adsorption (n), the charge transfer coefficient (α), and, finally, the rate constant (ks). The process of adsorption of H2O2 on each of the characteristic metallic planes was further studied via Monte Carlo simulations (MCSs). We accounted for both molecular O2 and H2O during the simulations to understand the effects of oxygen and solvent on adsorption since all experiments were conducted in an air-saturated solution. Several numbers of the adsorbate-metal substrate configurations were obtained for the simulations on each crystalline Pd plane, confirming the firm adsorption of H2O2 in the presence of O2 and H2O. Based on analysis of the results from the electroanalytical procedures and MCSs, possible reduction reaction mechanism pathways were proposed.