The Construction and Application of Dual‐Modified Carbon Nanotubes in Proton Exchange Membranes with Enhanced Performances

Abstract In this study, the carbon nanotubes (CNTs) are successively coated via sol‐gel method with SiO 2 (SiO 2 @CNTs), followed by grafting with 3‐merraptnpropyltrimethnxysilane and oxidation with hydrogen peroxide to yield dual‐modified CNTs (SSiO 2 @CNTs). The SSiO 2 @CNTs material is applied to prepared chitosan (CS) based composite proton exchange membranes by the incorporation of various content of SSiO 2 @CNTs, the structure and properties of as‐prepared composite membranes are fully investigated. Compared to pristine CS membrane, the SSiO 2 @CNTs‐filled composite membranes show improved thermal stability, mechanical stability, and methanol resistance, owing to the effective interface interaction and good compatibility between SSiO 2 @CNTs and CS matrix. Additionally, the doping of SSiO 2 @CNTs also generates a positive effect on the electrochemistry performance, due to the construction of abundant transport channel and providing more proton sources or proton sites. Particularly, the CS/SSiO 2 @CNTs‐7 membrane exhibits tensile strength of about 40.1 MPa and proton conductivity of 35.8 mS cm −1 at 80 °C, which is almost 1.6 and 2.0 times higher than pure CS membrane, and lower methanol permeability of 0.9 × 10 −6 cm 2 s −1 . The direct methanol fuel cell performance (DMFC) of CS/SSiO 2 @CNTs‐7 membrane is also improved with open circuit voltage of 0.67 V and maximum power density of 60.7 mW cm −2 at 70 °C.