Development of self-assembling sulfonated graphene oxide membranes as a potential proton conductor

A simple method is reported for the preparation of self-assembling sulfonated graphene oxide membranes (SGO-X) to be studied as a potential proton conductor for proton exchange membrane fuel cells (PEMFCs). The effect of three different sulfuric acid-to-GO molar ratios is investigated, the main aim being the identification of an optimal sulfonation interval ensuring a successful trade-off among composition, structural stability and functional properties. ATR-FTIR and EDX spectroscopies, SEM, thermogravimetry and static contact angle measurements allow to analyze the efficacy of the functionalization of graphene oxide (GO) with sulfonic acid groups (-SO3H) and the uniformity of the component's structure. A preliminary examination of the proton conductivity is performed on the most promising samples (SGO-1, SGO-20) by means of electrochemical impedance spectroscopy (EIS), together with the evaluation of water uptake, ion exchange capacity and degree of sulfonation. This introductory work demonstrates that the proposed SGO-X membranes exhibit notable water-retaining and proton-exchanging properties at elevated temperatures and reduced humidity, compared to pristine GO and Nafion 212 benchmark specimens. Therefore, these innovative self-standing materials are proved to be worthy of additional studies for the optimization of their features, foreseeing the assessment of their behavior as a possible electrolyte in a PEM fuel cell.

Automated summary

This study presents a simple method for preparing self-assembling sulfonated graphene oxide membranes, investigating the effect of different sulfuric acid-to-graphene oxide ratios to find an optimal sulfonation interval. The membranes exhibit notable water-retaining and proton-exchanging properties, making them worthy of further optimization for potential use as electrolytes in PEM fuel cells.