Rationally Designed Solid Sorbent Electrolyte Exhibits Dual CO2/ H2O Sorption and Enables Full Gas Phase CO2 Reduction

Abstract Efficient CO 2 electrolysis hinges on high CO 2 availability and controlled water transport toward and away from the catalyst. Traditional methods, such as direct CO 2 supply in the gas form or using CO 2 sorbent liquid electrolytes face significant limitations. In this study, a pioneering approach is presented using a rationally designed CO 2 /H 2 O sorbent composite electrolyte, enabling low‐temperature aqueous CO 2 electroreduction without liquid catholyte nor anolyte. The development of a multi‐functional electrolyte in the form of a solid sorbent ionogel is introduced in this work. This novel material is designed to perform several tasks at once, namely 1) ensuring ionic conductivity (1.5‐3 mScm −1 ) in a solid material, thereby removing salt precipitation issues linked to liquid aqueous electrolytes, 2) serving as local CO 2 concentrator (0.03–0.13 mmol CO 2 /g for P CO2 0.1–1 bar at ) to pave the way for flue gas based feed streams at lower CO 2 partial pressures and 3) regulating water supply and removal (0.3–2.3 mmol H 2 O/g range at 85 % relative humidity depending on degree of methyl functionalization), to prevent preferential hydrogen evolution. This work offers a proof‐of‐concept for full‐vapor phase CO 2 reduction, where methyl‐functionalization of an ionic liquid‐silica nanocomposite enable to steer the selectivity from H 2 to CO production.