Active parts for CH4 decomposition and electrochemical oxidation at metal/oxide interfaces by isotope labeling-secondary ion mass spectrometry
Teruhisa Horitaa, , , Haruo Kishimotoa, Katsuhiko Yamajia, Natsuko Sakaia, Yueping Xionga, Manuel E. Britoa, Harumi Yokokawaa, Muneaki Raib, Koji Amezawab and Yoshiharu Uchimotob
aNational Institute of Advanced Industrial Science and Technology (AIST), Central 5, Higashi 1-1-1, Tsukuba, Ibaraki 305-8565, Japan bGraduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
Received 7 May 2006; revised 21 July 2006; accepted 31 July 2006. Available online 12 September 2006.
Active parts for CH4 decomposition and electrochemical oxidation of reformed gases were investigated at the well defined Ni-mesh/oxide interfaces in μm level. The effective reaction areas were determined by isotope labeling technique under the mixture of CH4, D2O, and 18O2 at 1073 K. A deposition of carbon preferentially occurred on the Ni-mesh surface on Y2O3-stabilized ZrO2 (YSZ) and Sm2O3-doped CeO2 (SDC) electrolyte oxides. A slight reduction of carbon deposition was observed on SDC substrate under non-polarized condition. The electronic and structural properties changes of Ni were observed by XANES/EXAFS analysis. By anodic polarization, a significant reduction of deposited carbon was observed on Ni-mesh surface in Ni-mesh/YSZ and Ni-mesh/SDC samples. Oxygen spill over can be effective for eliminating the deposited carbon on the Ni-mesh. Hydrogen and isotope oxygen concentration (18O2) on the Ni-mesh was changed by the oxide substrates under anodic polarization.
Keywords: Solid oxide fuel cells (SOFCs); Anode/electrolyte interfaces; Isotope labeling; Secondary ion mass spectrometry (SIMS); XANES/EXAFS