Incorporating graphene oxide into COF membranes enables ultrahigh proton conductivity and ultralow H2 crossover

Proton exchange membranes (PEMs) are the core components of electrochemical hydrogen energy production, storage and conversion devices. It is a great challenge to develop PEMs with a combination of high proton conductivity, minimal H 2 crossover and mechanical robustness for achieving high efficiency and long-term stability in these devices. Here, a co-assembled PEM composed of ionic covalent organic framework (iCOF) nanosheets and functionalized graphene oxide (GO) nanosheets was presented. The iCOF (TpPa-SO 3 H) nanosheets and polydopamine-modified graphene oxide (DGO) nanosheets were co-assembled into TpPa-SO 3 H/DGO mixed nanosheets with ultrahigh aspect ratio, which were readily further processed into TpPa-SO 3 H/DGO co-assembled membranes. The abundant and uniformly distributed –SO 3 H groups on TpPa-SO 3 H nanosheets and the acid-base pairs formed between TpPa-SO 3 H and DGO nanosheets promoted proton conduction significantly. Additionally, the dense structured DGO nanosheets inhibited H 2 crossover remarkably, and the multiple interactions between TpPa-SO 3 H and DGO nanosheets enhanced mechanical strength . The resultant TpPa-SO 3 H/DGO co-assembled membrane exhibited an ultrahigh proton conductivity of 916.4 mS cm −1 (80 °C, 100% RH), an unprecedently low H 2 crossover of 9.7 barrer and a sufficient tensile stress of 87.8 MPa. The enhanced proton conduction and H 2 barrier property led to enhanced performance in both electrochemical hydrogen compression and single hydrogen fuel cells.