Morphology of size-selected Ptn clusters on CeO2(111)

Stability of oxidized states of free-standing and ceria-supported PtOx particles

Nanostructured materials based on CeO2 and Pt play a fundamental role in catalyst design. However, their characterization is often challenging due to their structural complexity and the tendency of the materials to change under reaction conditions. In this work, we combine calculations based on the density functional theory, a machine-learning assisted global optimization method (GOFEE), and ab initio thermodynamics to characterize stable oxidation states of ceria-supported PtyOx particles in different environments. The collection of global minima structures for different stoichiometries resulting from the global optimisation effort is used to assess the effect of temperature, oxygen pressure, and support interactions on the phase diagrams, oxidation states, and geometries of the PtyOx particles. We thus identify favoured structural motifs and O:Pt ratios, revealing that oxidized states of free-standing and ceria-supported platinum particles are more stable than reduced ones under a wide range of conditions. These results indicate that studies rationalizing activity of ceria-supported Pt clusters must consider oxidized states, and that previous understanding of such materials obtained only with fully reduced Pt clusters may be incomplete.

Exploring the materials space in the smallest particle size range: From heterogeneous catalysis to electrocatalysis and photocatalysis

Ultrasmall clusters of subnanometer size can possess unique and even unexpected physical and chemical propensities which make them interesting in various fields of basic science and for potential applications, such...

Atomic structures and local electronic properties of K- and Rh-modified ceria/Pt(111) inverse model catalysts

Ceria has been widely applied as a support in heterogeneous catalysis due to its unique capability to store and release oxygen. As a typical inverse model catalyst, a ceria/Pt(111) system has attracted much attention due to its strong metal-oxide interaction. The structural and electronic properties of the ceria/Pt(111) system can be effectively modified by the introduction of alien K and Rh atoms. Here, the K- and Rh-modified ceria/Pt(111) inverse model catalysts have been investigated with high resolution scanning tunneling microscopy and apparent local work function measurement. The experimental results indicate that the K atoms prefer to occupy the top sites of the stoichiometric ceria, while the Rh atoms are prone to stay at the electron-rich ceria island edges. The K and Rh atoms act as an electron donor and acceptor on ceria/Pt(111), respectively. Such a study on the modification of the ceria-based catalysts should help understand strong metal-oxide interaction in heterogeneous catalysis at the atomic level.