A Generalized One-Step Synthesis Of Three-Dimensional Network-Like Noble Metals And Their Alloy Nanostructures

Noble metals often exhibit good chemical stability, physical and chemical properties, electrical properties and high catalytic activities. Thus, they are widely used in electro-catalysis, petroleum refining, sensors and fuel cells etc industres and high-tech areas. Although porous or network-like nanomaterials have demonstrated improved catalytic performance over solid counterparts, developing a simple and gerneralized method to prepare three-dimensional porous network structures (3DPNN) still remained challenged. Therefore, it is of intensive interest to develop a new, simple and uviersal approache to create three dimensional networks of noble metals and their alloys.In this thesis, we design a facile one-step high-yield strategy to synthesize3DPNN of metals and alloys including Pt, Pd, Au, Ag, Pt-Pd, Pd-Ru, Pd-Au, Pd-Cd,Pt-Cu, by introducing the thermodynamic control of interparticle interactions and heat-induced interparticle fusion into the nucleation and Ostwald ripening process. In addition, the morphology, composition, electrocatalytic activity of the samples and mechanism were systematically studied by XRD, SEM, TEM, HTEM, STEM, EDS, IR, CV, i-t curve and Zeta Potential, respectively. The main results are listed as follows:1. We report a universial one-step strategy to synthesize noble metal3DPNN by introducing of interparticle fusion and the modulation of electrostatic repulsion during the nucleation and growth of metals. DTAB molecules are adopted to adsorb on the surface and make the as-formed Pt nuclei and seeds be positively charged. The modulation of the electrostatic repulsion potential (Velect) of charged nuclei and seeds at150℃can successfully result in the formation of, Pt3DPNN composed of～20nm nanoparticles (or rod-like units). This simple synthesis method can also be extented to prepare other noble metals (Pd, Au, Ag) and noble metal alloys (Pt-Pd, Pd-Ru, Pd-Au, the Pd-Cd, Pt-Cu)3DPNN. Furthermore, the size and composition of3DPNN can be adjusted by varying the molar amount and the molar ratio of metal precursors.2. By adopting the charged Au NPs as the artificial atoms (nuclei or seeds), the moderate adjustment of the interparticle electrostatic repulsion and fusion effect can lead the transformation of Au NPs into Au3D networkstructured nanomaterials. The additional example of Au3DPNN strongly confirms that the strategy proposed of combination of heat-induced interparticle fusion with the modulation of Velec during the nucleation and growth of materials to prepare metal and alloy3DPNN is reasonable and expected to develop a general one-step method to fabricate3DPNN.