Preparation Of Ag(Pt)-based Nanocomposites Using Sacrificing Template Method And Their Catalytic And Sers Properties

The development of the synthetic technology of nanomaterials has made it possible to homogeneously incorporate a single component into the composite materials.Synergy between different components can endow new functions of the nanocomposites.In recent years,preparation of noble metal nanomaterials with controlled morphology and size has become a hot research topic,with applications in many fields,such as optics,sensing,and electrochemistry.However,high cost of production,introduction of pollutants in the reduction process,and agglomeration of nanoparticles lead to the limited application and promotion of precious metal nanomaterials.This dissertation presents a method of preparing Ag and Pt nanocomposites using intermediate valence transition metal oxides as sacrificial templates.With advantages of mild experimental conditions and atomic economy,this method is conductive to the preparation of high-performance and high-purity noble metal nanomaterials.Intermediate valence transition metal oxides?Cu₂O and Mn₃O₄?were used as the reducing agent and nucleation sites for noble metal nanoparticles?Ag,Pt?.Cu₂O/Ag nanocomposites,Ag/Ag₂S/Ag₃CuS₂ nanocomposites,and Pt/Mn₃O₄-rGO nanocomposites have been successfully prepared.These multi-component nanocomposites have been used for SERS-based molecule detection,photocatalysis under visible light,and catalytic oxygen reduction reaction?ORR?.Galvanic replacement reaction between sacrificial intermediates?Cu₂O and Mn₃O₄?and Ag+/Pt4+ ions for the preparation of noble metal nanomaterials mainly depends on the potential differences.It possible to prepare noble metal nanomaterials and nanocomposite materials with controllable particle size and morphology.Especially,when the galvanic replacement reaction during the preparation of Ag/Cu₂ O and Pt/Mn₃O₄-rGO nanocomposites is not completed,the nanocomposites can maintain the three-dimensional morphology as the sacrificial templa tes.The Ag and Pt based nanocomposites prepared by this method have the advantages of clean surface,novel and homogeneous microscopic morphology,endowing the nanocomposites with better catalytic and molecule detection performance.Branched Cu₂ O crystal s are prepared by electrodeposition method on the surface of ITO glass.Reaction between Cu₂ O and Ag+ ions induced by different acid catalysts?5-sulfosalicylic acid,citric acid,lactic acid,camphor sulfonic acid?leads to formation of Ag/Cu₂ O nanocomposites.It was found that only 5-sulfosalicylic acid can make the Ag nanoparticles grow uniformly on the Cu₂ O matrix,because complexation of 5-sulfosalicylate with Ag+ ions determines the nucleation and growth of Ag particles.Ag/Cu₂ O was used as SERS substrate for Raman detection of methylene blue?MB?,rhodamine B?RhB?and urea solution in the physiological concentration range.The results show that the detection limit of MB and RhB can reach 10-9 mol/L,and the trace and quantitative detection of urea molecules can be achieved by establishing the relationship between the concentration of urea and the integral Raman intensity.Reaction between branched Cu₂ O crystal and Na₂ S can produce Cu₂O@Cu₇S₄ core-shell structures,and Cu₇S₄ shells can be obtained after corrosion of Cu₂ O core by NH3·H₂O.Galvanic replacement reaction between Cu₇S₄ and Ag+ ions can generate rose-like Ag/Ag₂S/Ag₃CuS₂ nanocomposite materials.By controlling the reaction time and doping acid?citric acid,tannic acid,camphorsulfonic acid,benzoic acid?,the morphology of Ag/Ag₂S/Ag₃CuS₂ nanocomposites can be regulated,and The nanocomposites are used for SERS-based molecular detection and photocatalysis.The results show that the SERS performance of Ag/Ag₂S/Ag₃CuS₂ nanocomposites is not as good as that of Ag nanoparticles,but is better than that of Cu₇S₄.Ag/Ag₂S/Ag₃CuS₂ nanocomposites obtained at a reaction time of 10 min have best catalytic performance for the degradation of MO under visible light.It is determined that the superoxide ani on radicals?·O2-?and holes?h+?are the catalytic active species.rGO-Mn₃O₄ nanocomposites are constructed by growing homogeneous Mn₃O₄ nanoparticles on the rGO surface,and galvanic replacement reaction between Mn₃O₄ and H₂ Pt Cl6 generates Pt/Mn₃O₄-rGO ternary nanocomposites.The size,distribution and content of Pt nanoparticles are changed by adjusting the amount of H₂ Pt Cl6.The electrocatalytic oxygen reduction reaction?ORR?activity of Pt/Mn₃O₄-rGO nanocomposites with different Pt content are compared.With 2³ nm Pt nanoparticles uniformly distributed on the rGO-Mn₃O₄ carrier and a Pt loading of 10.06 wt%,the as-prepared Pt/Mn₃O₄-rGO nanocomposites can exhibit even better ORR catalytic activity as compared with commercial 20 wt% Pt/C,indicating tha t the prepared nanocomposites can have stronger electrocatalytic performance at low Pt loading.