Enhancing Conductivity in PEM Chitosan Membranes through Bisphosphonate Graphene Oxide

Abstract

Proton exchange membranes (PEM) are a key component on several electrochemical devices, such as fuel cells and electrolysers, and hold great promises for various technological applications. However, their properties, including their limited proton conductivity, remain a significant challenge. In this study, a novel approach to improve the conductivity of chitosan membranes was used, through the incorporation of bisphosphonate graphene oxides (BPGO) as dopants. Starting from two graphene oxide materials with different oxidation levels, new BPGOs were achieved using a one-pot synthetic procedure. These dopants were characterized by ATR-FTIR and XPS spectroscopies. To improve the proton transport properties of membranes, new BPGO dopants were incorporated into the chitosan matrix, using a casting method, to achieve new chitosan doped membranes. These membranes were systematically studied to assess their proton conduction properties by impedance spectroscopy. The results demonstrate their the incorporation of these BPGOs dopants increases the proton conductivity of the membranes, with a significant increase in proton conductivity upon doping with high oxidation level BPGO, with a maximum enhancement of 1% (só ???) observed at an optimal doping level. The unique structure of BPGO, with its abundant functional groups and high specific surface area, facilitates the proton conduction of the membrane. Additionally, the presence of bisphosphonate groups improves the proton conductivity of the membrane, which increases with the increment of this functional group presents in the dopant.