Identifying the Critical Oxygenated Functional Groups on Graphene Oxide for Efficient Water Dissociation in Bipolar Membranes

Bipolar membranes (BPMs) are emerging options for kinetically accelerating water dissociation (WD) in electrochemical applications. Graphene oxide (GO) with abundant oxygenated functional groups is an efficient catalyst within BPMs to decrease the transmembrane potential. However, the dominant catalytic sites on GO for WD in BPMs have not been experimentally identified, and the reported simulative calculation results are controversial. Herein, we prepared carboxylated and partially hydroxylated GO-based BPMs, and for the first time quantitatively unraveled the correlativity between WD performance and carboxyl group content with tailor-designed experiments. By using a simple mechanical ball milling method, we further improved the bulk density of carboxyl on the GO catalyst, which achieved excellent WD performance during an operation of over 130 h operation. This study provides a subtle and facile strategy for catalyst design to advance BPM technologies.