Nickel-Palladium-Based Electrochemical Sensor for Quantitative Detection of Formaldehyde

Formaldehyde is a small organic molecule that has a wide range of uses in society despite its toxicity. Formaldehyde is classified as a known carcinogen by International Agency for Research on Cancer (IARC). Formaldehyde electrooxidation has become a subject of major interest in the recent past due to its potential application in fuel cell technology and the need for its detection at trace levels because of its toxicity. Many studies have been conducted on formaldehyde electrooxidation, most of which suffer electrode passivation as a result of adsorbed intermediates such as carbon monoxide adsorbed (COads) and formic acid adsorbed (H(2)COOads) formed from electrooxidation of formaldehyde. In this study a Nickel Palladium nanoparticles modified glassy carbon electrode (Ni-Pd/GCE) was fabricated for electrooxidation of formaldehyde. Palladium nanoparticles were electrochemically deposited onto a bare Glassy Carbon Electrode (GCE) from 2mM PdCl2 in 0.1M H2SO4 supporting electrolyte, at a controlled potential of -0.14V for 240 seconds. The Nickel nanoparticles were electrochemically deposited onto the PdGCE from 0.5M NiSO4 in 0.1M H2SO4 supporting electrolyte, at a controlled potential of -1.25V for 40 seconds. The modified glassy carbon electrode (Ni-Pd/GCE) was conditioned in 0.5M NaOH for about 50 cycles or more to obtain a reproducible voltammogram. The fabricated electrode was characterized using Cyclic Voltammetry (CV) and Chronoamperometry (CA). The results showed that the electrode had good electrocatalytic properties with respect to formaldehyde electrooxidation as a result of the synergistic effect of Ni and Pd nanoparticles combined with the glassy carbon technology. A sensitive oxidation peak for 1mM formaldehyde was observed at about 0.43V vs. Ag/AgCl/KCl (3M) in 0.5M NaOH, with a current density of 17mA/cm(2). It had a linear detection range from 10M to 1mM (R=0.9985) and a detection limit of 5.4M. The electrode showed significant electrocatalytic activity towards the electrooxidation of formaldehyde in aqueous solution, was selective, reproducible and stable, hence can be used to detect formaldehyde at trace levels and can find application in fuel cells.