Closed bipolar electrode for decoupled electrochemical water decontamination and hydrogen recovery

Abstract

To achieve safe recovery of H2 gas during water purification using the electrochemical oxidation (EO) process, we decoupled anodic oxidation and cathodic H2 evolution driven by reactions on closed bipolar electrodes with two poles in two separated solutions containing [Fe(CN)6]4−/3− as a soluble electron mediator. With increased current density of 1–16 mA cm−2, the anodic removal of phenol pollutant was increased from 37.28% (k = 0.0039 min−1) to 96.44% (k = 0.028 min−1), and meanwhile the cathodic H2 production was increased from 6.35 mL to 137.51 mL within 120-min electrolysis. The H2 gas was recovered at a coulombic efficiency (CE) of 71.77–99.88% and energy efficiency (EE) of 10.48–22.74%. The cyclic voltammetry (CV) scan results confirmed the capability of aqueous [Fe(CN)6]4−/3− redox couple to mediate electrolysis in the EO/C-BPE cell. This study provides a proof-in-concept demonstration of a spatially decoupled anodic oxidation and cathodic H2 production, making electrochemical water purification more secure, more economical and more sustainable. Keywords: Electrochemical oxidation, Closed bipolar electrodes, Water purification, Hydrogen recovery