High proton conductivity of the phosphate-linked graphene oxide monolith over a wide range from subzero to moderate temperature

Achieving proton-conducting solids with high proton conductivity at subzero temperatures remains a serious challenge. Thus, it is indispensable to develop the composites with high conductivity ranging from subzero to medium temperatures (243–343 ​K). Graphene oxide (GO) as an alternative matrix can provide the rich oxygen-containing groups. Thus, we prepared a series of proton conductors by covalently linking phosphate units onto the amino-functionalized GO monoliths (denoted NGOM-P), the structures of which are determined by FT-IR, XPS , XRD and Raman characterization techniques. Further, the fast proton transfer in effective acid-base networks in NGOM-P make the monolith achieve high proton conductivity from 2.61 ​× ​10 −2  ​S ​cm −1 (243 ​K) to 0.68 ​S ​cm −1 (343 ​K) under 98% relative humidity (RH).