Analytical TEM Observations of Combinatorial Catalyst Libraries for Hydrogen Production–As a Part of “MATERIOMICS”-

Abstract

Materiomics is a new approach combining combinatorial surveys and precise structure analyses in order to develop new functional materials efficiently. In this paper, we show the first stage of materiomics applied to metal/metal oxide catalysts. The catalytic activities of various metal/metal oxide catalysts for hydrogen production have been examined by a combinatorial method, and TEM observations have been performed for the selected catalysts from the libraries in order to estimate the structures in the combinatorial surveys. A Pd/MnO₂ catalyst shows the high activity for the water gas shift reaction, where thin Pd oxide layers about 1–2nm thickness are formed on the flat MnO₂ surface. However, Pd oxide layers are reduced and metallic Pd particles 2–3nm in diameter with narrow size distribution are formed after hydrogen reduction. The structure of manganese oxide support also changes after hydrogen reduction. On the other hand, both Pd particles with diameters of 2–3nm and 10–20nm on SiO₂ show low activity for the water gas shift reaction. Thus, it is concluded that the catalytic activity does not simply depend on the particle size of metals, but that the interaction between metals and metal oxide supports is also important for the catalytic performance.