Xiaojin Li

PROTIC IONIC LIQUIDS: AN ALTERNATIVE PROTON-CONDUCTING ELECTROLYTE FOR HIGH TEMPERATURE PROTON EXCHANGE MEMBRANE FUEL CELLS

A novel anhydrous proton-conductive membrane, composed of an ionic liquid tertiary amine phosphate as the electrolyte and polypropylene-nonwoven as the matrix, was first proposed and applied in high temperature proton exchange membrane fuel cells. The single cell fabricated with the PP-NW/[N111]·H2PO4 composite membrane gives a stable current density of 600 mA cm−2 under 140 °C and non-humidification conditions, making the proton exchange membranes based on ionic liquids much more prospective for high temperature proton exchange membrane fuel cells.

Study on hydrophobicity loss of the gas diffusion layer in PEMFCs by electrochemical oxidation

The hydrophobicity loss of the gas diffusion layer (GDL) in proton exchange membrane fuel cells (PEMFCs) was investigated by an accelerated stress test of electrochemical oxidation at a constant potential. The fresh and oxidized GDLs were characterized by cyclic voltammetry, contact angle measurements and water permeability. Results showed the occurrence of the oxidation of carbon and the decrease of the hydrophobicity of GDL. To discuss the reasons for the hydrophobicity loss, scanning electron microscopy, X-ray photoelectron spectroscopy and thermogravimetry were analyzed. It was found that the hydrophobicity loss was closely associated with the losses of the carbon materials and polytetrafluoroethylene (PTFE) in GDL under test conditions. In addition, the mass loss of carbon materials was more than that of PTFE.

Development of proton-conducting membrane based on incorporating a proton conductor 1,2,4-triazolium methanesulfonate into the Nafion membrane

In this paper, 1,2,4-triazolium methanesulfonate (C2H4N+3CH3SO−3, [Tri][MS]), an ionic conductor, was successfully synthesized. It exhibited high ionic conductivity of 18.60 mS·cm−1 at 140°C and reached up to 36.51 mS·cm−1 at 190°C. [Tri][MS] was first applied to modify Nafion membrane to fabricate [Tri][MS]/Nafion membrane by impregnation method at 150°C. The prepared composite membrane showed high thermal stability with decomposed temperature above 200°C in air atmosphere. In addition, the membrane indicated good ionic conductivity with 3.67 mS·cm−1 at 140°C and reached up to 13.23 mS·cm−1 at 180°C. The structure of the [Tri][MS] and the composite membrane were characterized by FTIR and the compatibility of [Tri][MS] and Pt/C catalyst was studied by a cyclic voltammetry (CV) method. Besides, the [Tri][MS]/Nafion membrane (thickness of 65 µm) was evaluated with single fuel cell at high temperature and without humidification. The highest power density of [Tri][MS]/Nafion membrane was 3.20 mW·cm-2 at 140°C and 4.90 mW·cm-2 at 150°C, which was much higher than that of Nafion membrane.

High Temperature PEM Fuel Cells Based on Nafion®/SiO2 Composite Membrane

1.1 High temperature PEMFC Polymer electrolyte membrane fuel cell (PEMFC) is considered to be one of the most promising alternative energy conversion devices for motor vehicles and other stationary applications, due to its quick start, high energy efficiency, and environmentally friendly qualities(Marban and Vales-Solis 2007). At present, most PEMFCs are operated at 100°C) has many benefits (Yang, Costamagna et al. 2001; Li, He et al. 2003). Firstly, it avoids the existence of two phase flow in the flow field, thus enhances the stability & reliability of PEMFCs system. Then, operating PEMFC at a high temperature reduces the power loss caused by the electrochemical polarization of cathode. In addition, high temperature operation is also beneficial to make use of the exhaust heat of PEMFC system effectively and enhance the CO endurance of anode(Yang, Costamagna et al. 2001), etc. The key point of the HT-PEMFC is to develop a type of proton exchange membrane that can be endurable to the high temperature and still maintain high proton conduction. Because the most widely used commercial Nafion membrane is not competent for operating at high temperature due to dehydration. To solve this problem, many kinds of solutions have been proposed. Generally, these solutions can be divided into three catalogs as followings: a) to incorporate hydrophilic or proton conductive inorganic nano particles into the Nafion matrix to prepare so-called inorganic-organic composite membrane(Deng, Moore et al. 1998; Adjemian, Lee et al. 2002; Adjemian, Srinivasan et al. 2002; Costamagna, Yang et al. 2002; Shao, Joghee et al. 2004; Xu, Lu et al. 2005; Yonghao Liu, Baolian Yi et al. 2005; Adjemian, Dominey et al. 2006; Shao, Xu et al. 2006; Alberti, Casciola et al. 2007; Lin, Yen et al. 2007; Casciola, Capitani et al. 2008; Jian-Hua, Peng-Fei et al. 2008; Jin, Qiao et al. 2008; Jung, Weng et al. 2008; Rodgers, Shi et al. 2008; Wang, Yi et al. 2008; Yuan, Zhou et al. 2008; Santiago, Isidoro et al. 2009; Yan, Mei et al. 2009); b) to substitute the water in Nafion with non-volatile or low-volatile polar solvent; c) to prepare new material that can conduct proton independent of water(Deng, Moore et al. 1998; Adjemian, Lee et al. 2002; Yonghao Liu, Baolian Yi et al. 2005; Lin, Yen et al. 2007; Tang, Wan et al. 2007; Yen, Lee et al. 2007; Rodgers, Shi et al. 2008).