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Abstract: The intrinsic kinetic information for the dissociation of CH4 on the fresh Ni active sites was studied by pulsing CH4 through Ni/α-Al2O3 catalyst with different Ni particles. After the elimination of the mass and heat transfer, the conversions of CH4 were controlled far below the values of the thermodynamic equilibrium in order to keep the pulse reaction in the kinetic region. The coverage degree of carbon species on Ni active site is kept less than 1 to eliminate the influence of carbon deposition on the dissociation of CH4. The plot of versus the Ni particle size exhibits a “mountain” shape. The E a and ln A for the CH4 dissociation are linearly increased with the increase in the Ni particle size, showing the compensation effect in the CH4 dissociation. This work reveals that the CH4 dissociation on fresh Ni active site of Ni particles in Ni/α-Al2O3 catalysts is a structure sensitive reaction. [Copyright &y& Elsevier]

Abstract: A Pd layer was deposited on Nafion® membrane by electroless plating in order to reduce methanol crossover. The composite membrane was characterized by using the following techniques of X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDXS) and transmission electron microscopy (TEM). Methanol crossover was determined by the electrochemical method. The experimental results indicated that Pd film was successfully deposited onto the Nafion® membrane. The methanol permeability was effectively suppressed by the Pd layer, with methanol-related current decreasing from 64mA/cm2 (J lim) to 57mA/cm2 for 1M methanol and from 267mA/cm2 to 170mA/cm2 for 5M methanol, respectively. Furthermore, by employing the novel Pd-Nafion® composite electrolyte, the performance of single fuel cell was obviously improved with a high concentration of methanol such as 5M, indicating that depositing Pd layer onto the Nafion® membrane is an effective method to suppress the methanol crossover. [Copyright &y& Elsevier]