Design, Preparation And Characterization Of Titanium Dioxide Coated Carbon Nanotube/chitosan Proton Exchange Membrane

As proton exchange membrane(PEM)material,chitosan has advantages of environmental-friendly,low-cost and excellent methanol-blocking property.However,low proton conductivity limits chitosan using as PEM material.PEM is a core component of fuel cell,and the capability of fuel cell depends on the properties of PEM.We use anatase titania coated CNT(TCNT)to functionalize chitosan PEM,aiming to build more proton transfer channels which can enhance proton transfer.Here are two main reasons of functionalizing CNT:1)reduce agglomeration and improve dispersity of CNT;2)reduce CNT contact to get rid of short-circuiting phenomenon in fuel cell operation.A surfactant-warping method was adopted in TCNT preparation and different content of TCNT as dopant phase was doped in chitosan membrane to prepare CS/TCNT composite membrane.The structure and properties of composite membranes were analyzed.The results show that CS/TCNT-5 sample has the highest proton conductivity,0.01357 Scm-1 in room temperature,which is higher than 0.01046 Scm-1 of pure CS sample.A conclusion was reached that 5%is the best content to build proton transfer pathways in membrane.Meanwhile,methanol-blocking property was also intensified as methanol permeability reached 1.16×10-6cm2s-1,which was lower than 2.75×10-6 cm2s-1 of blank sample.And membrane selectivity of CS/TCNT-5 sample achieved 1.67×104 Sscm-1 as a result.To further improved the proton conductivity of composite membrane and fully facilitate the proton transfer pathways we introduced SLS to chitosan membrane in order to introduce sulfonate groups in membrane acting as proton hopping sites.The water uptake,oxidation stability,proton conductivity and methanol permeability of membrane samples was characterized.The results show that samples with SLS doped had better water uptake but a little worse oxidation stability,as proton conductivity was badly improved,CS/TCNT-5/SLS-2 sample reached a conductivity 0.03672 Scm-1 under room temperature and a selectivity of 28.16×104 Sscm-1.