Graduate School of Environmental Studies
Department of Frontier Science for Advanced Environment

A comprehensive understanding of the surface reactions on nano-sized metals (alloys), oxides, and carbon-based materials is essential in the development of novel nanomaterials with unique catalytic properties. Our approach involves (1) preparations of well-defined single crystal surfaces and nanoparticles of alloys and metal compounds through dry processes (molecular beam epitaxy and arc-plasma deposition; APD) in an ultrahigh vacuum (UHV) and (2) electrochemical evaluations of the catalytic properties of UHV-prepared nano-structural surface models that are intended for the development of practical electro-catalysts. We routinely use UHV and molecular-beam epitaxy, UHV-APD, scanning probe microscopy (SPM), scanning transmission electron microscopy (STEM), X-ray photo-electron spectroscopy (XPS), low-energy ion-scattering spectroscopy (LE-ISS), electrochemical (EC) voltammetry, gas chromatography (GC), online electrochemical mass spectrometry (OLEMS), and other techniques to clarify nanomaterials’ surface phenomena. Our research accomplishments provide a direct link to the next-generation hydrogen society.

Effect of Surface Strains on Pt-based Alloy Catalysts

We fabricated Pt/Co hetero-layered single crystal nanostructures with Pt(111)-shell layers by arc-plasma deposition in ultra-high vacuum environment and investigated effects of surface strains on the electrocatalytic oxygen reduction reaction (ORR) activity. The results demonstrated in-plane surface strain of ca. −2 % of the Pt(111)-shell vs. bulk Pt(111) gives the maximum activity enhancement.

Core-Shell Alloy Nanoparticles for Fuel Cell

We found that nitridation of PtCo nanoparticles lead the preferential core-shell (PtCo-core@Pt-shell) formation during electrochemical dealloying process for the alloy nanoparticles. The obtained PtCo@Pt core-shell nanoparticles exhibited ca. 10 times higher ORR activity than commercial Pt/C catalysts.