Saline water electrolysis system with double-layered cation exchange membrane for low-energy consumption and its application for CO2 mineralization

Abstract

Saline water electrolysis (SWE) plays a key role in mineralizing CO2 to carbonate products (e.g., NaHCO3) as it determines the conversion and energy efficiency of the whole CO2 mineralization process. SWE is highly energy intensive and cation exchange membranes (CEMs) represents the highest resistance contributing component of the overall system. Hence, the use of highly Na+ ion-conductive membranes can effectively reduce overpotentials and lower the energy consumption in a SWE system. Motivated by this, a double-layered cation exchange membrane composed of perfluorinated sulfonic acid (PFSA) and perfluorinated carboxylic acid (PFCA) ionomer layers is investigated as an alternative to the commercially available Aciplex-F® membrane, and its performance is evaluated in terms of current-voltage polarization, energy consumption, and caustic current efficiency in single cell mode, followed by technical reliability, electrochemical durability, and the purity of produced NaOH in stack mode. Finally, CO2 reduction achieved by replacing the conventional Aciplex-F based SWE system with the proposed CEM based SWE system is estimated for various electric power sources.