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

Abstract

Efficient CO2 electrolysis hinges on high CO2 availability and controlled water transport toward and away from the catalyst. Traditional methods, such as direct CO2 supply in the gas form or using CO2 sorbent liquid electrolytes face significant limitations. In this study, a pioneering approach is presented using a rationally designed CO2/H2O sorbent composite electrolyte, enabling low-temperature aqueous CO2 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 CO2 concentrator (0.03–0.13 mmol CO2/g for PCO2 0.1–1 bar at ) to pave the way for flue gas based feed streams at lower CO2 partial pressures and 3) regulating water supply and removal (0.3–2.3 mmol H2O/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 CO2 reduction, where methyl-functionalization of an ionic liquid-silica nanocomposite enable to steer the selectivity from H2 to CO production.