Creating a bipolar electrode system for electrochemical advanced oxidative processes with efficient electricity consumption

Abstract

Three-dimensional (3D) electrochemical processes have been developed as an effective device for electrochemical advanced oxidative processes (EAOPs) with improved catalytic efficiency compared with two-dimensional (2D) electrochemical processes. However, the catalytic efficiency of the 3D system was restricted by the limited polarized potential formed on 3D electrodes. Herein, a bipolar electrode (BPE) system was established inspired by bipolar electrochemistry using the graphite electrodes modified with graphite/TiO2 composites as the BPEs. Based on the theories of bipolar electrochemistry, the BPE system was analyzed in terms of electrochemical reaction process, operating parameters and energy consumption. Three pathways were revealed for •OH generation, including indirectly reduction, directly reduction and oxidation. As a result, the BPE system provided 26.813 mg/L •OH within 1 h at 2.0 V. The operating parameters were optimized with methylene blue (MB) as the model pollutant. The electricity consumption of the BPE system was calculated to be 4.0 kWh/kg of removed MB which showed 54% lower compared with a 3D system. The analysis on kinetics and thermodynamics of MB degradation exhibited an endothermic reaction in the BPE system. Furthermore, the in-situ experiment of thermal image visibly identified that the BPE performed an endothermic reaction induced by electrostatic potential. The outcomes of this study are dedicated to creating a controllable and high-efficiency BPE system for EAOPs via integrating bipolar chemistry and 3D system.