(676a) Engineering KW-Scale Reactors for Efficient and Selective CO2 Electrocatalysis

The development of efficient CO₂ electrolyzers is essential for advancing electrified and sustainable chemical manufacturing. However, current state-of-the-art CO₂ electrolyzers, including gas diffusion electrode (GDE) setups and membrane electrode assemblies (MEA), are typically limited to small electrode areas and low single-pass conversions, as energy losses and pressure drops escalate with increasing active area.

Here, we present the e-CO₂LUMN: a novel, high-pressure 20-stage CO₂ electrolyzer column for operation up to 40 bars, featuring over 2 m² of electrode area, 7.2 kW power rating. This vertically stacked design enables counter-current flow of gas-liquid streams, with optimized collection of liquid products. Fundamental mass, charge and energy balance analysis are used to define optimal operating conditions, including current density, cell voltage and Faradaic Efficiency.

To ensure safety compliance, detailed mechanical evaluations are performed using ASME Boiler and Pressure Vessel Code (BPVC) standards, addressing risks associated with pressure and material failure. A key innovation of the e-CO₂LUMN is its implementation of three sequential electrochemical reactions, enabling the stepwise conversion of CO₂ to CO, CO to Acetaldehyde and Acetaldehyde to Ethanol, for enhancement of selectivity and conversion rates.

High-porosity silver and Cu-based bimetallic foam electrocatalysts are employed to maximize active site availability across the large electrode area. A 50 cm² single-stage prototype is used for initial testing and optimization of the catalyst-membrane assembly. Scale-up from the 50 cm² to a 1000 cm² reactor is demonstrated by refining key design elements, including gas sparger configuration, electrocatalyst porosity, and membrane composition. The staggering of multiple stages to build the e-CO₂LUMN is also demonstrated, along with optimized mass and heat transport across multiple CO₂ conversion stages.

This work showcases a multi-scale, transport-driven approach to electrochemical reactor design optimizing for energy efficiency, selectivity, and scalability. The continued development of the e-CO₂LUMN system presents a promising pathway toward industrial-scale CO₂-to-fuel production.