Recently, new progress about the regulation of crystal phase of Platinum-based nanocrystals was made by the cooperation of Zhaoxiong Xie and Gang Fu group from Xiamen University. Related paper titled “Platinum-nickel alloy excavated nano-multipods with hexagonal close-packed structure and superior activity towards hydrogen evolution reaction”was published on the Nature Communications (DOI:10.1038/ncomms15131).

                    

Noble metal based nanomaterials are promising functional materials, which have potential applications in many important fields. The discovery of their new crystal phase provides an opportunity for achieving novel functionalities due to different atomic arrangements and electronic structures of allomorphs, and thus possesses great significance.Pt-Ni alloy is one of the best catalysts for many energy conversion applications, such as oxygen reduction (ORR) and hydrogen evolution (HER). In the past few decades, great efforts have been devoted to improving the catalytic efficiency through tailoring the size, morphology and composition of Pt-Ni alloy NCs, but all the reported Pt-Ni alloys adopt the typical face-centered cubic (fcc) crystal phase. The regulation of the crystal phase of Pt-Ni alloys was unrevealed.

Recently,Xie group reported a successful synthesis of metastable hexagonalclosed-packed (hcp) Pt-Ni alloy nano-multipods in a mild solvothermal condition for the first time. Detailed analysis showed that the building blocks of Pt-Ni alloy nano-multipods were highly-concave hexagonal prisms assembled by six nanosheets of about 2.5 nm in thickness and exposed with (11-20) facets. Owing to the unique crystal structure and large surface area due to the excavated polyhedral morphology, the hcp Pt-Ni alloy excavated nano-multipods exhibited a superior catalytic ability towards the HER. The specific area current density of hcp Pt-Ni excavated multipods at -70 mV is respectively 4.1 and 1.8 times higher than that of commercial Pt/C and their fcc counterpart. The mass current density of the as-prepared hcp Pt-Ni excavated nano-multipods reaches 3.28 mA µg_Pt^-1, which outperforms the currently reported catalysts. This work was supervised by Pro. Zhaoxiong Xie and associate Pro. Yaqi Jiang, the experimental sectionswere conducted by Zhenming Cao, Qiaoli Chen, Jiawei Zhang, Huiqi Li, Shouyu Shen, and Bang-an Lu, the theoretical calculations was carried out by Pro. Gang Fu.

This work was supported by the National Basic Research Program of China (Grants 2015CB932301), the National Natural Science Foundation of China (Grants 21333008, 21603178and J1030415), and the Natural Science Foundation of Fujian Province of China (No. 2014J01058).

Xie group has always been devoting in the research of the solid nanocrystals and related properties, and acquired great achievements in the regulation of the surface/intersurface of thermodynamical metastable nanocrystals. They successfully synthesized the metastable Au trioctahedron enclosed by high-index crystal surface {211} for the first time through wet-chemical means (Angew. Chem. Int. Ed. 2008,47,8901).Deduced from thermodynamics and theThomson−Gibbs equation that the surface energy ofcrystal face is in proportion to the supersaturation ofcrystal growth units during the crystal growth, they proposed that the exposed crystal faces can be simply tuned bycontrolling the supersaturation, and higher supersaturationwill result in the formation of crystallites with highersurface-energy faces(J. Am. Chem. Soc.2013,135,9311). They also put forward the concept of “excavated polyhedrons”, which has the well-defined crystal structure, large surface area and resistance fromaggregating, and reported a facile synthetic strategy for preparing excavated rhombic dodecahedral PtCu₃ alloy NCsconstructed of 24 ultrathin nanosheets with high-energy {110}facets(J. Am. Chem. Soc.2014,136,3748) and excavated cubic PtSn nanocrystals (Angew. Chem. Int. Ed.2016,31,9167) for the first time. Recently, Xie group summarised the syntheses and applications of the non-convex polyhedron, related review paper was published on Chemical Society Review (Chem. Soc. Rev.2016,45,3207).