Structural-enhanced bacterial cellulose based alkaline exchange membranes for highly selective CO2 electrochemical reduction and excellent conductive performance in flexible zinc-air batteries

In this work, OH– conducting membrane based on bacterial cellulose (BC) had been synthesized via modification with Poly(diallyldimethyl-ammonium chloride) (PDDA) and Poly(vinyl alcohol) (PVA) of different molecular weights using layer by layer method assisted by double cross-linking process. OH– conductivity and water uptake were intensively investigated by changing crosslinking conditions, KOH concentrations and different PVA molecular weights. Containing the maximum σOH− reached up to 72.95 mS cm−1 at room temperature with water uptake being 877%, the LPVA-PDDA-BC-OH– membrane showed the lowest calculated activation energy value of 10.211 KJ mol−1 indicating that both Grotthus and vehicle mechanisms played an important role on ionic transportation. During the application of CO2 electrochemical reduction (CO2ER) in 0.5 M KHCO3, the current density could reach up to 47.44 mA cm−2 at −1.06 VRHE while FEHCOO− achieved the maximum value of 67.89% which dampened only 7.09% after 20 h electrolysis. Furthermore, being assembled into the flexible zinc-air batteries (F-ZAB), the LPVA-PDDA-BC-OH– membrane exhibited excellent power density of 130.3 mW cm−2 at room temperature.