The catalytic activity was compared between Ni and Au electrodes on an Y2O3-stabilized ZrO2 (YSZ) substrate. Secondary ion mass spectrometry (SIMS) imaging analysis was applied to visualize the distribution of active parts for the decomposition Of CH4 and/or adsorption of reformed gases (H-2, O-2, CO, CO2, and C) around the metal/oxide interfaces. To analyze the metal/oxide interfaces in a submicrometer level, stripe-shaped metals (Ni and An) were prepared. Annealing in isotope-labeled gases was conducted at 973 K for 300 s in the mixture of CH4, O-18(2), and D2O. SIMS images and line analyses clearly showed the difference of catalytic activity for CH4 decomposition between Ni and Au; a significant carbon deposition was observed at the Ni-stripe surface, whereas almost no C at the Au-stripe. Isotope oxygen exchange (O-16/O-18 exchange) occurred on the Ni-stripe surface, whereas no reaction at the Au-stripe surface. Microstructure change of the stripe metals (both Ni and An) after label annealing was observed by scanning probe microscope (SPM). (C) 2004 Elsevier B.V. All rights reserved.