Formation of Hexagonal-Close Packed (HCP) Rhodium as a Size Effect.

Previous studies on the structural and functional properties of rhodium are based on the face-centered-cubic (fcc) structure in the bulk form. Here we report the first discovery of the hexagonal-close packed (hcp) rhodium in the nanoparticle form. The hcp Rh can be directly synthesized by solvothermal reaction or by electron-beam induced decomposition of Rh monolayers. The hcp Rh nanoparticles are stable under electron beam irradiation. Compared with the fcc structure, the hcp Rh nanoparticles show a large lattice expansion (6% larger atomic volume). The first-principles calculations suggest that the lower surface energy of hcp Rh leads to the size effect in the crystal structure.

Electrochemically Seed-Mediated Synthesis of Sub-10 nm Tetrahexahedral Pt Nanocrystals Supported on Graphene with Improved Catalytic Performance.

Controlling the surface structure of Pt nanocrystals (NCs), especially creating high-index facets with abundant active step sites, is an effective approach to enhance catalytic performances. However, the available high-index faceted Pt NCs have large particle sizes, which severely impedes their practical applications. In this study, we reported a new electrochemically seed-mediated method, by which sub-10 nm tetrahexahedral Pt NCs (THH Pt NCs) enclosed with {210} high-index facets supported on graphene were synthesized. Pt nanoparticles of ∼3 nm in size as high-density crystal seeds play a key role in the small-sized control. The obtained THH Pt NCs exhibited a higher mass activity than commercial Pt/C catalyst for ethanol electrooxidation. We further demonstrated that this method is also valid for reshaping commercial Pt/C, to create high-index facets on surfaces and thus to improve both mass activity and stability.

A new species of Nidirana (Anura, Ranidae) from northern Guangxi, China.

A new species of music frog, Nidiranaguibeiensis sp. nov., is described from northern Guangxi, China. Based on two mtDNA fragments analyzed, phylogenetic trees reveal that N.guibeiensis sp. nov. is most closely related to N.leishanensis. However, the new species can be identified by conspicuous diagnostic morphological characteristics as well as bioacoustics. In contrast to the known Nidirana species, the advertisement calls of the new species can be divided into three types, calls with one, two, and three notes. In addition, the new species has nest construction behavior, which is inconsistent with N.leishanensis. Nidiranaguibeiensis sp. nov. occurs in paddy fields or still pools at 300-1300 m a.s.l.