| Nanoporous silver (NPS) was fabricated by a simple dealloying method, and its formation mechanism was studied by corrosion condition controlling experiences. Based on the significative structure of NPS and its facile fabricating method, we further fabricated tubular nanoporous Pt/Ag, Pd/Ag bimetallic materials and porous AgCl/Ag nanocomposite. By means of TEM(Transmission Electron Microscopy), HRTEM(High Resolution Transmission Electron Microscopy), XRD(X-ray Diffraction), SAED(Select Area Electron Diffraction), EDS(Energy Dispersive X-Ray Spectrum) the surface morphology, crystal structure of these materials have been studied. Catalytic properties of these materials were explored by employing the electrochemical and photocatalytic test system. This paper was focusing on the developing of facile and environmental friendly fabrication method for effective catalytic material structure.1. Preparation of NPS by dealloying and the fabrication conditions study.The key point for the fabrication of nanoporous material by dealloying is to balance the dissolution speed of the more active element and the diffusion speed of the more inert element. Typically, NPS with sponge like uniform nanoporous surface can be fabricated by etching a piece of 50μm Ag23Al77 alloy in 1 M NaOH for 72 h at 30℃. The final morphology of the material was deeply related on the concentration/temperature of the corrosion solution and the corrosion time. Etching the same AgAl alloy in the HC1 solution can also obtain the nanoporous skeleton with bicontinuous pore ligaments companied with a rough surface. It is verified by the controlling experiments that the existence of Cl- can markedly accelerate the diffusion speed of Ag.2. Preparation and electrocatalytic performance of nanotubular porous platinum-group bimetallic nanocompositesDealloying was used to synthesize nanoporous metals to act as sacrificial templates, and followed by reacting with H2PtCl6 and K2PdCl4 solution precursors. Electron spectroscopy study revealed that the ligaments of the initial porous sturcture were completely hollow and the nanotubular porous bimetallic structures have been successively fabricated. The shell surface of the Pt/Ag material was smooth and seamless with tube diameter and shell thickness around 45 nm and 7nm respectively. The tube diameter and shell thickness of Pd/Ag material were around 40 nm and 5 nm respectively, and it has small holes with diameter of～4 nm on the shell. Crystal structure study approve the both of the two material were alloy. During the electrochemical test, Pt/Ag material exhibits high catalytic activity and CO-tolerance toward methanol oxidation. These nanostructures have obvious structural advantages in terms of unique catalytic properties, simple and clean processing, and saving precious metals, which suggest their great potential for use in heterogeneous catalysis and fuel cell technologies.3. Fabrication of porous AgCl/Ag nanocomposites and its visible light catalysis.Porous AgCl/Ag nanocomposites were fabricated with a facile two-step route, which involves the formation of nanoporous silver (NPS) by dealloying AgAl alloys, and a subsequent surface chlorination in a mixed solution containing H2O2 and HCl. Morphology study revealed a porous AgCl/Ag composite nanostructure that inherited the bicontinuous spongy morphology of NPS precursors with interconnected pore channels and solid ligaments. The existence of Ag in the structure was found to contribute greatly to enhanced absorption in the visible light region. In a test system for the degradation of methylic orange (MO) dye, it was found that porous AgCl/Ag nanocomposites performed very well as efficient and stable visible light catalysts. Under non-optimized conditions, the MO dye degradation rate can reach as high as 0.75 mg/min·gcat with 420 nm irradiation. It is believed that porous AgCl/Ag and similar structures will be promising nanostructured visible light photocatalysts useful for environmental science and technology.
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