Imidazolium group prompted alkaline anion-exchange membrane with high performance for efficient electrochemical CO2 conversion

Abstract

Development of high-performance hydroxide-conductive membranes is a focus research subject owing to promising applications in electrochemical reduction of CO2 (eCO2RR). However, few satisfactory membranes have been developed to maximize the performance of CO2 electrolyzers, despite its role as the core in regulating ion transport and preventing product crossover or fuel loss. Herein, we report the synthesis of alkaline anion-exchange membranes fabricated by poly (vinyl-alcohol) (PVA) and poly [(3-methyl-1-vinylimidazoliummethylsulfate)-co-(1-vinylpyrrolidone)] (PQ44) for use in CO2 electrolysis. Owing to the unique imidazolium ring structure coupled with a three-dimensional semi-interpenetrating porous internal architecture, the PVA/PQ44-OH- membranes provide a high hydroxide conductivity (21.47 mS cm−1), preferable mechanical property and thermal stability. In particular, the eCO2RR used PVA/PQ44-OH- as electrolyte membrane realized a charming Faradaic efficiency (88%) and partial current density (29 mA cm−2) at −0.96 VRHE and, delivered the excellent durability over 20 h electrolysis in 0.5 mol L−1 KHCO3 electrolyte. Notably, it can even enable an ultrahigh current density beyond 100 mA cm−2 at −1.11 VRHE when the electrolyte was KOH instead, and produced the FEHCOO− of 85% at a low potential of −0.81 VRHE, superior to both commercial alkaline A201 and acidic Nafion117 membrane.

Keywords

• Alkaline anion-exchange membrane
• Imidazolium ring structure
• Semi-interpenetrating network
• CO2 electroreduction
• Formate production