Electrochemical Removal of Gaseous Acetaldehyde Using Ag-Hg Bimetallic Catalyst with a Liquid-Free Electrolyte

Abstract

Electrochemical methods have been widely used to remove gaseous pollutants that are dissolved in liquids. However, there have been no significant attempt made to remove gaseous pollutants in their gas state, especially through electrochemical method. In this study, we attempted to remove gaseous acetaldehyde (AA) through electro-oxidation using an Ag-Hg bimetallic catalyst coated on a Ni foam electrode at a gas–solid interface. The interface was induced by a semi-solid agar gel in a membrane-divided electrolytic cell. We confirmed the formation of Ag-Hg on the Ni foam electrode through X-ray photoelectron spectroscopy and scanning electron microscopy. We also found that the semi-solid gel was a suitable solid electrolyte, as evidenced by the absence of discernible redox peaks in cyclic voltammetry analysis and the high charge transfer resistance in electrochemical impedance analysis. Under inlet conditions of 15 ppm with a flow rate of 200 mL min−1, we could achieve up to 80% AA degradation. This was due to the effective transfer of electrons in the presence of the semi-solid gel, which was eight times higher than that obtained in the zero-gap method. In continuous operation of the electrochemical reactor with a single-pass of AA, we consistently achieved a removal capacity of 169.81 mg cm−2 h−1 over a 1-h period in an Ar atmosphere. These results demonstrate the practical applicability of this electrochemical system developed using a liquid-free electrolyte and a bimetallic catalyst for the electrode.