Electrochemical Fabrication Of Coral-like Gold Nanostructure And Its SERS And Electrocatalytic Properties

Gold nanomaterials have wide applications in the fields of catalysis, biosensing, SERS, energy conversion and storage due to their unique properties, such as optics, mechanics, magnetism, electronics and thermotics etc. Up to date, preparations of Au nanomaterials have involved various strategies, where electrodeposition is one of the most popular ways because of its simple operation and easy adjustification. In this thesis, controllable three-dimensional(3D) coral-like Au network nanostructures(GNs) were synthesized electrochemically, and their SERS and electrocatalytic performance were explored as follows:1. Three-dimentional Au nanocoral network structures(3DGNs) were prepared by one-step electrodeposition by chronopotentiometric involving ammonium bromide as the additive. The morphology, size and the electrochemical characteristics of as-prepared 3DGNs were further characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), high-resolution transmission electron microscopy(HRTEM), energy dispersive X-ray spectrum(EDX) and electrochemical cyclic voltammometry. Also, the growth process and mechanism of 3DGNs were preliminarily explored by investigating the effect of electrodeposition time, the amount and types of additives, the applied current density on 3DGNs, optimizing the experimental conditions to produce high-quality 3DGNs. Additionally, as-prepared 3DGNs can be disassembled into individual gold nanoparticles by ultrasonic treatment, achieving the large-scale production of Au nanoparticles by electrochemical techniques.2. SERS properties of 3DGNs fabricated with different electrodeposition time were further investigated. The SERS enhancements of all 3DGNs are close to 106. With the increase of electrodeposition time, the number density of 3DGNs and the size of their branches increase and correspondingly the SERS signals are enhanced. When the electrodeposition time is up to 45 min, the 3DGN has the best SERS enhancement and reproducibility. When the electrodeposition time is increased over 45 min, the SERS enhancement, on the contray, decreases. It indicates that the enhancement efficiency and reproducibility of 3DGNs depend on their fine structures and the size of the branches of 3DGNs. 3DGN prepared with 45-min electrodeposition may has a potential application in analytic detection due to its excellent SERS activity and reproducibility.3. Ptn/3DGN were prepared by decorating Pt on the surface of 3DGN fabricated with 45-min electrodeposition and its elecrocatalytic performance towards formic acid was investigated. Ptn/3DGN were prepared by combining the underpotential deposition(UPD) of Cu and the redox replacement reaction(RRR) between Cu and Pt Cl62-(UPD-RRR). Pt contents on the surface of 3DGN can be tuned by controlling the times of UPD-RRR. The results indicate that Ptn/3DGN can efficiently electrooxidize formic acid. The Pt1/3DGN with ~50% coverage of Pt on 3DGN shows the best electrocatalytic activity and stability, ~22 times in the specific activity better than that of the commercial Pt/C. It may attribute to the domination of the direct oxidation of formic acid, completely eliminating the production of the poisoning species, such as CO.