Chitosan/sulfonated graphene oxide/silica nanocomposite membranes for direct methanol fuel cells

Abstract

Silica nanoparticles on sulfonated graphene oxide (sGO/SiO2) are incorporated with chitosan (CS) in tunable compositions and their performances as ion conductors in direct methanol fuel cells (DMFC) are evaluated. The morphological observations reveal that sGO/SiO2 nanocomposite is homogeneously distributed throughout the CS matrix. The anisotropic and strong bonds created among the carbon atoms of functionalized GO nanosheets and the ceramic characteristic of SiO2 nanofillers promote the thermal stability of CS/sGO/SiO2 composite membrane than that of bare CS membrane. The hydrophilic sites provided via the sulfonated moieties of GO and hygroscopic characteristics of SiO2 nanoparticles improve the water adsorption channels. The hydrogen bonding and acid-base pair interaction exerted between the CS and sGO/SiO2 facilitate the continuous and rapid ion conduction via grotthuss mechanism. The high aspect ratio of sGO and the effectively piled SiO2 nanoparticles generate tortuous channels for methanol diffusion. Thus the selective passage of ions and fuel in CS/sGO/SiO2 composite membrane provides the maximum DMFC power density of 87.18 mW cm−2 with considerable duration, which confers the prosperous light on the utility of environmentally benign and bio-degradable CS membrane in DMFCs.