Fabrication of bacterial cellulose membrane-based alkaline-exchange membrane for application in electrochemical reduction of CO2

As the core component of the electrochemical reduction of CO2 (ERC), alkaline anion-exchange membranes (AEMs) in a CO2 electrolyzer can not only transport hydroxide ions as conductors, but also prevent fuel crossover between two electrodes and reduce fuel loss. However, the membrane is threatened by low conductivity and poor stability. In this paper, AEMs based on polymer composites of bacterial cellulose (BC)/poly (diallyl dimethyl ammonium chloride) (PDDA) are developed for use in ERC, via a proposed impregnation, chemical cross-linking and ion-exchange process. The effects of crosslinking conditions and different BC:PDDA mass ratio on the hydroxide-ion conductivity, water content, microscopic and macroscopic morphological structure, and stability of BC-PDDA-OH- membrane are thoroughly evaluated. The hydroxide-ion conductivity, incorporating BC:PDDA = 1:0.5 mass ratio, remains at 28.5mS cm(-1) and 17.89 mS cm(-1) after the membrane soaking in 0.5 M KHCO3 and 0.5 M KOH solution for 720 h, respectively. At an applied potential of -0.96V(RHE), the BC-PDDA-OH- membrane exhibits the highest Faradaic efficiency of 50.84% for formate (FEHCOO-) in 0.5 M KHCO3 electrolyte, and the FEHCOO- only attenuates by 8.85% after 20 h of continuous electrolysis. In comparison, the BC-PDDA-OH- membrane in 0.5 M KOH electrolyte produced the FEHCOO- of 50.92% at an applied potential of -1.006V(RHE). The electrochemical performances of both systems are superior to that of commercial acidic Nafion117 and commercial alkaline A901 membranes, which prove the feasibility of BC membrane fabricated AEMs application in high performance of ERC.

Automated summary

This study develops AEMs based on polymer composites of bacterial cellulose and poly(diallyl dimethyl ammonium chloride), which exhibit good hydroxide-ion conductivity and stability for CO2 electrolyzer application. The membrane shows a high Faradaic efficiency of 50.84% for formate ions in 0.5M KHCO3 electrolyte, indicating its potential for high performance in ERC.