Areas like the chemical industry and the oil refining industry depend on selective catalysis. Due to this the development of highly efficient catalysts has become a priority for some researchers.
In recent years, two-dimensional noble metal nano-materials have drawn a great deal of research interest due to their superior catalytic activity in many reactions.
Phase engineering has recently emerged as a popular research field in noble metal-base nano-materials. Following this, heterophase nano-structure have demonstrated successful catalytic performance.
This has been demonstrated by research conducted by Hongfei Cheng et al: “For the first time, amorphous/crystalline heterophase PdCu nano-sheets with high purity…have been synthesised…The amorphous phase-dominant PdCu nano-sheets..were synthesised at a reaction temperature of 40°C.”
Despite this breakthrough, it is still very difficult to synthesise ultrathin two-dimensional noble metal-based nano-alloys with an amorphous/crystalline herophase. The atomic isotropy of the amorphous phase makes it challenging to obtain the two-dimensional structure. Additionally, the thermodynamically stable phase of noble metals demonstrates a close crystalline structure due to the strong atomic interaction. Subsequently, it is thermodynamically unfavourable for it to form an amorphous phase and the two-dimensional structure.
The study continued to explain how: “Phase engineering is arising as an attractive strategy to tune the properties and functionalities of nano-materials. In particular, amorphous/crystalline heterophase nano-structures have exhibited some intriguing properties. Herein, the one-pot wet-chemical synthesis of two types of amorphous/crystalline heterophase PdCu nano-sheets is reported, in which one is amorphous phase-dominant and the other one is crystalline phase-dominant. Then the ageing process of the synthesised PdCu nano-sheets is studied, during which their crystallinity increases, accompanied by changes in some physicochemical properties.”
During the ageing process, the crystallinity of a-PdCu gradually increased, which was accompanied with changes in some other physico-chemical properties, including electronic binding energy and surface ligand adsorption. Consequently, the chemo-selectivity and catalytic activity of the heterophase PdCu nano-sheets also changed in the hydrogenation of 4-nitrostyrene.