Guangjin Wang

SC-IrO 2 NR-carbon hybrid: A catalyst with high electrochemical stability for oxygen reduction

The enhanced electrochemical stability of the synthesized hybrid catalyst has been demonstrated by the introduction of the synergistic effect between carbon powder additive and the prepared catalyst. Single crystal IrO2 nanorod (SC-IrO2NR) catalyst was prepared by a sol-gel method. The structure and performance of the catalyst sample were characterized by X-ray diffraction spectroscopy (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), rotating disk electrode (RDE) and cyclic voltammetry (CV) measurements. XRD patterns and TEM images indicate that the catalyst sample has a rutile IrO2 single crystal nanorod structure. The onset potential for oxygen reduction reaction (ORR) of the SC-IrO2NR-carbon hybrid catalyst specimen is 0.75 V (vs. RHE) in RDE measurement. CV and RDE test results show that the SC-IrO2NR-carbon hybrid catalyst has a better electrochemical stability in comparison with the commercial Pt/C catalyst, with attenuation ratios of 17.67% and 44.60% for the SC-IrO2NR-carbon hybrid catalyst and the commercial Pt/C catalyst after 1500 cycles, respectively. Therefore, in terms of stability, the SC-IrO2NR-carbon hybrid catalyst has a promising potential in the application of the proton exchange membrane fuel cell.

Structure-dependent electrocatalytic activity of La 1- x Sr x MnO 3 for oxygen reduction reaction

The electrocatalytic activity toward oxygen reduction reaction is studied on the perovskite oxide La1-xSrxMnO3, as prepared under different firing temperatures. X-ray diffraction shows that three different crystal phases featuring tetragonal, cubic, and orthorhombic symmetries form with increasing crystallinities. The electrocatalytic activity is characterized by cyclic voltammetry and linear sweeping voltammetry for the three phases of La1-xSrxMnO3. We find that the tetragonal phase has the best catalytic activity among the three crystal phases, with the largest onset potential of 0.147 V. The synergistic effect between the volume per unit cell and crystallinity is indicated to account for the good catalytic activity of the tetragonal phase.

Catalytic activity of iridium dioxide with different morphologies for oxygen reduction reaction

Iridium dioxide with different morphologies (nanorod and nanogranular) is successfully prepared by a modified sol-gel and Adams methods. The catalytic activity of both samples for oxygen reduction reaction is investigated in an alkaline solution. The electrochemical results show that the catalytic activity of the nanogranular IrO2 sample is superior to that of the nanorod sample due to its higher onset potential for oxygen reduction reaction and higher electrode current density in low potential region. The results of Koutecky-Levich analysis indicate that the oxygen reduction reaction catalyzed by both samples is a mixture transfer pathway. It is dominated by four electron transfer pathway for both samples in high overpotential area, while it is controlled by two electron transfer process for both samples in low overpotential area.