Abstract
In order to obtain biopolymer chitosan-based proton exchange membranes with excellent mechanical properties as well as high ionic conductivity at the same time, natural attapulgite (AT) with one-dimensional (1D) structure was loaded with a strong heteropolyacid and also a super proton conductor, phosphotungstic acid (PWA), using a facial method. The obtained PWA anchored attapulgite (WQAT) was then doped into the chitosan matrix to prepare a series of Chitosan (CS)/WQAT composite membranes. The PWA coating could improve the dispersion and interfacial bonding between the nano-additive and polymer matrix, thus increasing the mechanical strength. Moreover, the ultra-strong proton conduction ability of PWA together with the interaction between positively charged CS chains and negatively charged PWA can construct effective proton transport channels with the help of 1D AT. The proton conductivity of the composite membrane (4 wt.% WQAT loading) reached 35.3 mS cm−1 at 80 °C, which was 31.8% higher than that of the pure CS membrane. Moreover, due to the decreased methanol permeability and increased conductivity, the composite membrane with 4% WQAT content exhibited a peak power density of 70.26 mW cm−2 fed at 2 M methanol, whereas the pure CS membrane displayed only 40.08 mW cm−2.
Highlights
Direct methanol fuel cell (DMFC) is a highly efficient and eco-friendly energy conversion device that can directly convert chemical energy into electrical energy by using liquid methanol as the anode fuel
Phosphotungstic acid immobilized on attapulgite (WQAT) was prepared using the following main three steps: Firstly, AT was ultrasonically dispersed in a H2SO4 solution (2 M) at 60 ◦C for 2 h
Super-strong proton conductor, PWA, anchored AT was prepared and directly used as a novel nanofiller employed in the chitosan matrix to fabricate composite proton exchange membranes
Summary
Direct methanol fuel cell (DMFC) is a highly efficient and eco-friendly energy conversion device that can directly convert chemical energy into electrical energy by using liquid methanol as the anode fuel. Wen and co-workers designed and prepared functionalized carbon nanotubes (CNTs) with different surface coating substances (such as chitosan, sulfate zirconia, SiO2, TiO2, organic long-chain ions) to modify CS to fabricate a series of composite membranes [14,15,16,26,28] These surface coating materials can promote the dispersion of CNTs, and fully play the reinforcement role of CNTs, and improve the proton conductivity due to the newly formed proton conducting network along the surface of functionalized CNTs. Apart from 1D CNTs, 1D clay nanotubes or nanorods have been used as an effective additive in the field of PEMs. Wang et al [21] synthesized halloysite nanotubes bearing sulfonated polyelectrolyte brushes (SHNTs) via distillation-precipitation polymerization and added into CS matrix to prepare nanohybrid membranes. The single direct methanol fuel cell performance was tested
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