Strengthen the Performance of Sulfonated Poly (Ether Ether Ketone) As Proton Exchange

Strengthen the performance of sulfonated poly (ether ether ketone) as proton exchange membranes with phosphonic acid functionalized carbon nano-tubes

Wen Zhang*, Hui Zheng, Chengyi Zhang, Baochen Li,Feifei Fang and Yuxin Wang

School of Chemical Engineering and Technology, State Key Laboratory of Chemical Engineering, Co-Innovation Center of Chemical Science & Engineering, Tianjin Key Laboratory of Membrane Science and Desalination Technology, Tianjin University, Tianjin 300072, PR China

∗ To whom correspondence should be addressed. E-mail: . Tel.: (+86) 22-27890515.

Contents

1 System for through-plane proton conductivity measurement 1

2 X-ray photoelectron spectroscopy (XPS) spectra of CNT-POH 2

3 The stress–strain curves of SPEEK, SPEEK-COH and SPEEK-POH 3

1 System for through-plane proton conductivity measurement

Through-plane proton conductivity was measured by AC impedance spectroscopy (electrochemical workstation, PARSTAT 2273, 90 USA) between 0.1 kHzand1MHz. The Through-plane proton conductivity (S/cm) is determined from the membrane resistance R (Ω), the thickness of the membrane L (cm), and the cross-sectional area through which the current passes A(cm2).

The measurement of through-plane membrane resistance was carried by the membrane test system (MTS 740, Scribner Associates, Inc.), and the schematic representation of the assembly used for our measurements is showed in Fig. S1. The humidity and temperature were real-time control. The Pt catalyst/carbon paper was prepared in the following way:Pt/C(20 wt% Pt, Johnson Matthey, UK) were used as catalysts. The catalysts were mixed with deionized water, Nafion ionomer solution (5 wt%, Aldrich), and isopropylalcohol in an ultrasonic bath at ambient temperature for 30 minto obtain homogeneous catalyst inks. Carbon papers (Toray; 10 and20 wt% Teflonized) were used as diffusion layers.The catalyst inks were applied to the Teflonized carbon paper by a spraying technique. The Pt loadings were 2.0mg/cm2on the carbon papers.

Fig. S1 Schematic representation of the assembly used for the measurements

2 X-ray photoelectron spectroscopy (XPS) spectra of CNT-POH

Fig. S2 X-ray photoelectron spectroscopy (XPS) spectra of CNT-POH

The most intense photoelectron peaks are found at 980 eV, 533 eV, 285 eV, 191 eV, 154 eV, 133 eV, and 103 eV, which are attributed to O KLL, O 1s, C 1s, P 2s, Si 2s, P 2p, and Si 2p electron configurations respectively. The XPS results therefore confirmed that phosphorus and silicon was successfully introduced into the surface of CNT.

3 The stress–strain curves of SPEEK, SPEEK-COH and SPEEK-POH