Toward a Stackable CO₂-to-CO Electrolyzer Cell Design─Impact of Media Flow Optimization

Abstract

Aqueous CO 2 -to-CO electrolysis is a promising technology for closing the carbon cycle and defossilizing industrial processes. Considering the technological readiness, consensus has been achieved about using silver as a stable and selective electrocatalyst for the CO 2 -to-CO reduction reaction in aqueous electrolyte. On the other hand, challenges such as media flow management, component stability, and force distribution are still associated with improving the process performance and developing a stackable cell concept to meet industrially relevant levels. We therefore report on a promising stack concept with continuous flowcells operated with gas diffusion electrodes (GDEs). To enhance the CO 2 -to-CO conversion efficiency, dedicated media flow chambers were developed on two levels. In the gas chamber, which touches the GDE from the far side of the anode, the feed gas flow and distribution over the GDE were controlled by introducing various gas path architectures in a modular flowcell. In addition, an ionically conductive spacer was implemented in the catholyte chamber, which is adjacent to the opposite side of the GDE. The effect of these modifications on the cell voltage, selectivity, and overall conversion was investigated at 100 mA/cm 2 with varying CO 2 feed gas flow and concentration. Noteworthy, an optimized feed gas distribution generated an increase of the Faraday efficiency for CO under reduced CO 2 supply. Furthermore, the implementation of the spacer enhanced the process stability by suppressing gas-bubble-induced noise in the cell voltage measurements. By functioning as support structures to the GDE, the combined modifications provided the cell with mechanical integrity and allowed an ionic and electric contact over the full active cell area, which is required for both stacking and upscaling of the cell. The corresponding performance was demonstrated by a two-cell short-stack.

CO2 flow electrolysis – limiting impact of heat and gas evolution in the electrolyte gap on current density

“…The gas compartment consisted of a titanium flow field with a meandering channel. 18 This flow field also served as the electrical contact for the GDE. A zero-gap counter electrode consisting of an Ir-MMO coated titanium mesh (mesh size: 2 mm × 4 mm, Metakem) was used in the cell.…”

“…The authors kindly acknowledge funding by the Federal Ministry of Education and Research (BMBF), Project: iNEW2.0 “Inkubator Nachhaltige Elektrochemie” Funding code: 03SF0627A. The authors thank M. Quentmeier for designing the titanium flow frame, 18 M. Turiaux for supplying gaskets to assemble the GDE flow cell, and A. Luft for his dedicated maintenance of the lab equipment.…”

Advances and challenges in membrane electrode assembly electrolyzers for CO2 reduction

“…Moreover, MEA electrolyzers offer the advantage of easy scalability and assembly into stacks, making them highly suitable for industrial applications. 41,42 Janaky et al 43 demonstrated the industrial potential of electrochemical CO production by utilizing commercial silver nanoparticles as catalysts in a multiple electrolyzer stack. The stack was congured with both parallel and serial connections, showcasing the versatility of the system.…”

Design of Carbon Dioxide Reduction Electrolysis Stacks and Trial Production of Electrolytic Cell Prototype

“…While conductivity is not a significant concern, better thermal conductivity can enhance heat transfer efficiency in the system. Common materials used for the supporting shell include stainless steel and polymer materials such as polytetrafluoroethylene (PTFE) and polyphenylene (PPL) [15] . To ensure high air tightness and prevent leakage and seepage, the surface of the flow cell requires a certain degree of smoothness and excellent corrosion resistance.…”