Reducing CO₂ from air by trapping it in a foam concentrator

Résumé :

The increasing concentration of atmospheric carbon dioxide (CO₂) requires the development of complementary strategies for its capture and conversion into value-added products. This thesis investigates two complementary approaches within the framework of carbon capture and utilization (CCU): CO₂ transport through aqueous foams and electrochemical CO₂ reduction to carbon monoxide (CO) using silver nanowire (AgNW) gas diffusion electrodes. A dedicated experimental system was developed to investigate gas transport through foams while simultaneously monitoring their structural evolution. The results demonstrated preferential CO₂ transport relative to O₂ in foamed systems, while experiments with binary and ternary gas mixtures highlighted the influence of gas composition and headspace geometry on transport behavior. AgNWs were synthesized using a modified polyol method and optimized through control of halide-based nucleation conditions before being integrated into gas diffusion electrodes. The resulting electrodes exhibited high selectivity toward CO₂ reduction to CO, with faradaic efficiencies up to 90% in both a flow cell and a zero-gap electrolyzer. Operation at 200 mA cm⁻² demonstrated the potential of the AgNW architecture for high-rate CO₂ electrolysis, while a CO₂ conversion efficiency of 34% was achieved at a reduced CO₂ flow rate. Despite stable electrochemical performance over several hours, post-electrolysis characterization revealed nanoscale restructuring of the AgNWs and partial removal of the PVP capping layer. This thesis provides complementary insights into CO₂ transport and electrochemical conversion, establishing a basis for further development of foam-based gas transport systems, and for improving the stability of AgNW-based electrodes.​​​​​

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Contact : irig.communication@cea.fr