Proton-Conducting Composite Membranes with Graphene Oxide and (3-mercaptopropyl) Trimethoxysilanefor Hydrogen Fuel Cells

Graphene oxide membrane (GOM) has outstanding electrolyte properties in electrochemical devices, such as fuel cells, electrolyzers, and batteries. In proton exchange membrane fuel cells (PEMFCs), perfluorinatedsulfonic acid (PFSA) membrane, i.e., Nafion^®, is used as an electrolyte, which has disadvantages in the fuel cells application, such as fuel crossover, expensive, difficult manufacturing process, and many more. However, GOM has a much lower proton conductivity in through plane (σ_th) compared to Nafion^® due to anisotropic properties of GOM, and the loss of surface functional groups due to reduction by hydrogen is accompanied by an increase in electron conductivity when in contact with hydrogen gas in a fuel cell. Therefore, in this study, an MPTS-modified GO composite (MGC) was synthesized using a high-viscosity GO solution (5 mg/ml) and a dilute (3-mercaptopropyl)trimethoxysilane(MPTS, HS(CH₂)₃Si(OCH₃)₃) (0.790 g/mL) (MPTS) and this was followed by impregnation of excess MPTS as a binding agent for MGC.The thiol group of the MPTS monomer is oxidized by hydrogen peroxide (H₂O₂) to a sulfonic acid group (-HSO₃), providing a fast proton conduction path with negative oxygen functional groups on the GO particle surface.The optimum weight of incorporation was analyzed by examining the amount of MPTS from 1 to 70 wt% in the GOM matrix. The physicochemical properties, gas crossover, chemical and thermal stability and proton conductivity of composite membranes were studied and compared with pristine GOM and Nafion^®. In addition, hydrogen-permeable Pd was deposited on the surface of the MGC membrane to improve gas tightness and maintain high mechanical stability to prevent membrane degradation and reported the performance of hydrogen fuel cells using synthesized MGC membranes.