Comparison of catalytic activity for CH 4 decomposition at the metal/oxide interfaces by isotope-labeling technique

Abstract

The catalytic activity was compared between Ni and Au electrodes on an Y 2O 3-stabilized ZrO 2 (YSZ) substrate. Secondary ion mass spectrometry (SIMS) imaging analysis was applied to visualize the distribution of active parts for the decomposition of CH 4 and/or adsorption of reformed gases (H 2, O 2, CO, CO 2, and C) around the metal/oxide interfaces. To analyze the metal/oxide interfaces in a submicrometer level, stripe-shaped metals (Ni and Au) were prepared. Annealing in isotope-labeled gases was conducted at 973 K for 300 s in the mixture of CH 4, 18O 2, and D 2O. SIMS images and line analyses clearly showed the difference of catalytic activity for CH 4 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 ( 16O/ 18O exchange) occurred on the Ni-stripe surface, whereas no reaction at the Au-stripe surface. Microstructure change of the stripe metals (both Ni and Au) after label annealing was observed by scanning probe microscope (SPM).