Tri-phase interface regulation of ionomer-encapsulated Ag/C catalyst for industrial CO₂ electrolyzer: A DOE-based analysis

Carbon monoxide (CO) stands as one of the most valuable and economically viable products in the electrochemical reduction of CO₂. In this study, we introduced high-surface-area porous carbon and anion-exchange ionomer to silver nanoparticles, rapidly constructing a tri-phase interface that enhances CO₂ transport and proton conduction. The ionomer-encapsulated tri-phase interface further improves reaction selectivity by increasing HCO₃⁻ concentration. Flow cell tests revealed that the 80% Ag/C catalyst doubles the partial current density of CO as compared to commercial Ag nanoparticles. To integrate the synthesized 80% Ag/C into industrial-scale membrane electrode assembly (MEA) electrolyzers (10 cm × 10 cm), we developed a comprehensive evaluation system incorporating CO selectivity, cell voltage, and actual gas conversion ratio (λ_act) with only one piece of MEA. This approach allowed systematic evaluation of current density and gas flow rate effects, followed by operational parameter optimization to 300 mA·cm⁻² and 1000 standard cubic centimeters per minute (sccm). Under optimal conditions, the 80% Ag/C catalyst demonstrated stable operation for over 60 h with a cell voltage of 3 V. The observed CO Faradaic efficiency decay rate suggests a projected operational lifetime exceeding 500 h. This work not only presents an efficient modification strategy to enhance the CO₂ reduction performance of silver-based catalysts, but also establishes a design-of-experiment (DOE) methodology for industrial-scale testing conditions optimization, thereby facilitating the advancement of CO₂ reduction reaction (CO₂RR) toward practical industrial applications.