Shahjahan Chowdury1,Young Cho1,Sung Park1,Yong-il Park1
Kumoh National Institute of Technology1
Shahjahan Chowdury1,Young Cho1,Sung Park1,Yong-il Park1
Kumoh National Institute of Technology1
Graphene oxide membrane (GOM) is considered a promising alternative electrolyte due to its hydrophilic nature and fascinating proton conductivity in humidified conditions. However, GOM has a lower proton conductivity than high-performance Nafion<sup>(R) </sup>membrane in the through-plane direction (σ<sub>th</sub>) and GOM loses its surface functional groups by hydrogen gas in anode when operating in PEMFC, resulting in increased electronic conductivity. Therefore, in this research, a highly proton-conducting composite membrane was synthesized using a silanization process between a highly viscous GO solution (5mg/mL) and a diluted (3-mercaptopropyl) trimethoxysilane (MPTS, HS(CH<sub>2</sub>)<sub>3</sub>Si(OCH<sub>3</sub>)<sub>3</sub>) (0.790 g/mL). The organofunctional group of the thiol group (-SH) was oxidized by hydrogen peroxide (H2O2) into a sulfonic acid group (-HSO3) on the surface of GOM for providing a high-speed proton conduction path along with the functional group of GOM. Moreover, proton conductivity was raised by adding excess MPTS as a binder in the MPTS-modified GO composites (MGCs). The incorporated MPTS into the GO framework was controlled from 1 to 70 wt%, and a suitable ratio of the high-performance electrolyte properties was reported such as excellent proton conductivity, thermally, mechanically and chemically protected from degradation. In addition, the MPTS-derived siloxane structure further enhances the water uptake with dimensional stability and low fuel crossover without damaging the proton transport path in MGCs. The synthesized composite membrane was investigated not only the morphology by FE-SEM, but also the molecular and microstructure analysis using powder X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis/differential scanning calorimetry, and UV-Vis spectroscopy. In addition, hydrogen-permeable 40 nm- thick Pd was deposited on the surface of the MGCs to improve the gas tightness and maintain high mechanical stability to prevent degradation of the membrane by hydrogen reduction during the operation of the fuel cell.