Efficiency and energy consumption analysis of bipolar membrane electrodialysis for electrochemical CO2 capture

Abstract

Bipolar membrane electrodialysis (BMED) is an electricity-driven technology that captures and purifies CO₂, but its efficiency remains poorly understood. This work quantified coulombic efficiency losses in BMED for carbon capture using a fully saturated (1 M KHCO₃) and a partially saturated KOH solvent. Fully saturated solutions required 50% less energy consumption than partially saturated solutions for CO₂ purification and solvent regeneration. The minimum specific energy consumption was 161.2 kJ per mol CO₂ (3.65 GJ per ton CO₂) at 100 A/m² and was limited by parasitic potassium transport across the bipolar membrane, resulting in low CO₂ desorption efficiency (<60%) at low current density. Additionally, incomplete CO₂ desorption represented up to 10% of efficiency losses in most of the conditions tested. BMED displayed 100% CO₂ desorption efficiency (mol CO₂ per mol e⁻) and a specific energy consumption of 290.61 kJ per mol CO₂ (6.60 GJ per ton CO₂) at industrially relevant current densities (1000 A/m²). This work presents a robust analytical framework to identify coulombic efficiency losses and identifies the cause for low CO₂ desorption efficiency at a wide range of current densities and operational conditions, providing unique insights into the transport mechanisms in BMED and unlocking new pathways to maximize technology performance.