An Electro-Reductive Removal of Gaseous Toluene By a Copper-Nickel Complex Mediator at Gas-to-Solid Interface

Abstract

Electrochemical technique is one of the most promising methods for the removal of volatile organic compounds such as toluene. However, the conventional gas electrolysis method has mass transfer limitation, and the homogeneous catalysts are often irrecoverable after the reaction is completed, which leads to inefficient, less environmental-friendly, and uneconomical performance. This study proposes a gas-to-solid electrolysis system employing an electrode coated with heterogenous catalyst as the electron transfer mediator. A CuNi(CN)4 complex was prepared according to a published method and drop-coated on a commercial copper mesh electrode with 5% Nafion solution. The CuNi(CN)4 coated copper electrode was further covered by 10 M of NaOH solution by drop-coating to increase the pH, which in turn widens the potential window. The prepared CuNi(CN)4 electrode was characterized by XRD and SEM-EDS analyses. The XRD and SEM-EDS analyses evidenced the CuNi(CN)4 presence with structural and composition details. Characteristics of electrodes and mediators were also confirmed through various analysis methods. Additionally, an electrochemical confirmation of CuNi(CN)4 presence by its redox behavior was inferred by gas-phase cyclic voltammetry. After confirmation of mediator presence, electrode mounted in a Nafion membrane divided electrolytic cell at the cathodic half-cell for the gas phase reductive electrolysis. A PVA gel was inserted in-between the Nafion membrane and the cathode to serve as a solid electrolyte to facilitate the electron transfer process. The electrochemical reduction of gas-phase toluene was carried out using a continuous flow model and chronoamperometry method. Different experimental parameters such as feed gas flow rates and concentrations were investigated on toluene removal. GC-MS analyses were applied to measure toluene concentration and intermediate compounds identification. A possible reaction mechanism will be discussed in detail at the conference. Acknowledgment This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education(NRF-2021R1I1A1A01049901) and also from the Grants No. NRF-2020R1A6A1A03042742