Sulfonated polythiophene-interfaced graphene for water-redispersible graphene powder with high conductivity and electrocatalytic activity

The production of redispersible graphene, especially in an aqueous medium, is highly desirable for its practical applications. In this study, we develop a simple route for the production of water-redispersible graphene powder by interfacing graphene with an amphiphilic polymer, poly[2-(3-thienyl)ethyloxy-4-butylsulfonate] sodium salt (PTEBS), via exfoliation-assisted noncovalent functionalisation. The PTEBS-interfaced graphene flakes can be self-dispersed in the aqueous phase without the presence of excessive stabilisers. The interfacial interactions between pristine graphene and amphiphilic PTEBS molecules and the intrinsic colloidal structure of their dispersions at the nanoscale were studied using ultra-small/small angle neutron scattering (U/SANS) with contrast-variation for the first time. It is found that the strong noncovalent pi-stacking interaction between graphene and the hydrophobic thiophene rings of PTEBS disrupts the pi-pi interactions holding the graphite layers and promotes exfoliation; whereas, the sodium sulfonated moieties of PTEBS render hydrophilicity to the exfoliated graphene. A water-redispersible graphene powder based on pi-stacking of PTEBS molecules is produced, which shows excellent capabilities for the formulation of graphene inks for the printing of flexible conductive circuits (similar to 30 omega sq-1) and metal-free electrocatalyst layers for the oxygen reduction reaction (ORR), which reduce O2 molecules to OH- ions through the highly efficient four-electron pathway and exhibit superior durability under a methanol crossover effect. The surface of pristine graphene is engineered toward hydrophilicity by interfacing with amphiphilic PTEBS molecules, creating a new class of water-redispersible graphene with high conductivity and electrocatalytic activity for energy applications.