Lamellar composite membrane with acid-base pair anchored layer-by-layer structure towards highly enhanced conductivity and stability

Abstract

Graphene oxide (GO) lamellar membranes have attracted intensive attentions in membrane separations due to the ultrafast molecule transport, but are seldom utilized as proton exchange membrane because of the inferior proton conduction and water stability. Herein, we demonstrate the fabrication of acid-base pair anchored lamellar composite membrane, by layer-by-layer assembling dopamine modified GO (DGO) nanosheets and phosphorylated bacterial cellulose (PBCn), for conquering the trade-off between proton conductivity and water stability. The abundant −PO(OH)2 groups on PBCn form acid-base pairs with –NH2/−NH− groups on DGO nanosheets. The acid-base pairs serve as low-energy-barrier proton transfer highways; meanwhile impose strong attractive force on adjacent GO layers. In this way, the lamellar composite membrane exhibits 244.9% enhancement of in-plane conductivity over GO membrane at 90 °C and 100% RH, and keeps stable in water medium even after 14 days. Moreover, the through-plane conductivity that determines fuel cell performance, gains 9.9 times augment (vs. GO membrane). Consequently, the transfer anisotropy coefficient significantly decreases from 15.5 to 4.9, thus offering a 128.9% enhancement in maximum power density (182.9 mW cm−2). Furthermore, the acid-base pairs impart membrane a high tensile strength of 203.5 MPa, surpassing most previously reported freestanding laminar membranes.