(720e) Sulfonated Silica Particles As Proton-Conductive Porous Solid Electrolytes for CO2 Electrolysis

The CO₂ reduction reaction (CO₂RR) is a promising route for turning CO₂ into useful chemical feedstocks, helping tackle both environmental and industrial challenges. One of the ongoing issues is that the liquid products through CO₂RR usually contain dissolved electrolytes, which require extra separation steps. Using porous solid electrolytes (PSEs) in electrochemical reactors could help avoid that, producing cleaner outputs. In this work, we developed silica-based particles as a potential PSE for CO₂ electrolysis. We grafted sulfonated silane ligands onto mesoporous silica and tested two different ligands: 2-(4-chlorosulfonylphenyl)-ethyltrimethoxysilane and 3-(trimethoxysilyl)propane-1-sulfonic acid. Particle sizes ranged from 20 nm to 40 μm to see how size impacts conductivity and performance in a continuous-flow setup. Smaller particles showed better ionic conductivity up to 5.31 × 10^-2 S cm, showing a trade-off between particle size and ionic conductivity. When we integrated the silica PSEs into a CO₂ electrolyzer, we reached over 90% Faradaic efficiency toward formic acid. This study introduces a new class of solid-state electrolytes with broad potential for CO₂ electrolysis and related electrochemical systems.