Preparation Of Pt-based Nanostructures And Study Of Electrocatalytic Properties

Platinum nanocrystals with particular shapes show superior physical and chemical properties due to their high catalytic activity and selectivity for many catalytic reactions.Thus,it has been widely used as catalyst in the oil industry,automobile exhaust purification,fuel cells and other major areas of energy and the environment.Till now,it is still a hot research field that how to reduce the amount of platinum under the premise of improving the electrocatalytic activity and selectivity due to the scarcity of platinum.In this work,we synthesize platinum-based nanomaterials with different morphologies by using different methods.Meanwhile,the as-prepared platinum-based nanomaterials with especial morphologies are applied in various electrochemical fields such as the electrochemical detection of hydrogen peroxide,electrocatalytic reduction of oxygen and electrocatalytic oxidation of methanol,etc..Main researches are as follows.1.The water-soluble phosphonate functionalized spherical platinum nanoclusters(Pt-NCs)composed of primary nanoparticles are synthesized by the thermal decomposition of platinum(IV)-complex.The size,morphology and structure of Pt-NCs are analyzed by dynamic light scattering(DLS)and transmission electron microscopy(TEM).Attachment of phosphonate groups on Pt surface is confirmed by Fourier transform infrared(FT-IR)spectroscopy,X-ray photoelectron spectroscopy(XPS),and zeta potential analysis.The phosphonate functionalized Pt-NCs efficiently suppress the oxygen reduction reaction(ORR)while fully preserving the Pt-like activity for the hydrogen peroxid reduction reaction.Importantly,at certain cathodic potential,only reduction reaction of hydrogen peroxide occurs at the Pt-NCs surface.Consequently,the phosphonate functionalized Pt-NCs can be used to fabricate a new kind of hydrogen peroxide electrochemical sensor with high performance in the presence of oxygen.Under optimized experimental conditions,the hydrogen peroxide electrochemical sensor shows fast response(less than 2 s)and wide linear range(1.0×10-6 to 1.0×10-3 M)in the presence of oxygen.The results presented here indicate an important new direction in the quest to design selective catalysts for the fribcation of noble-metal based H2O2 electrochemical sensor.2.Three-dimensional platinum nanochains networks(Pt-3NCNWs)nanostructures are synthesized through thermal decomposition method using platinum(IV)-complex as reaction precursors in absence of surfactants and templates.The size,morphology and surface composition of Pt-3NCNWs are investigated by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS).These spectral studies confirm as-papered products are three-dimensionally interconnected networks nanostructures with primary Pt nanochains as building blocks,and Pt nanochains grow from the primary spheric Pt nanoparticles via oriented attachment.Compared to the commercial Pt black catalyst,the Pt-3NCNWs nanostructures exhibit superior electrocatalytic activity and stability towards oxygen reduction reaction,which is ascribed to their unique properties such as the few surface defect sites and the low hydroxyl surface coverage on one-dimensional Pt nanochains,as well as fast O2 diffusion in three-dimensional structures.3.We design and synthesize a multiwalled carbon nanotubes(MWCNTs)supported platinum nanochains(Pt-NCHs)catalyst(Pt-NCHs/MWCNTs)through the electrostatic self-assembly between phosphonate functionalized Pt-NCHs and polyallylamine(PAH)functionalized MWCNTs.The grown mechanism,morphology,structure,and composition of the Pt-NCHs are investigated by ultraviolet-visible(UV-vis),transmission electron microscopy(TEM),X-ray diffraction(XRD),X-Ray photoelectron spectroscopy(XPS)and zeta potential analysis.XPS and elemental maps measurements confirm the successful immobilization of PAH on the MWCNTs surface.The resultant Pt-NCHs/MWCNTs catalyst exhibits better electrocatalytic activity for the oxygen reduction reaction(ORR)than the commercial Pt/C catalyst due to the unique structure and low hydroxyl surface coverage.4.Three-dimensional(3D)platinum-cobalt alloy networks nanostructures with the high alloying degree are synthesized through the room temperature wet-chemical synthetic method using the K2PtCl4/K3Co(CN)6 cyanogel as reaction precursor in absence of surfactants and templates.The size,morphology and surface composition of platinum-cobalt alloy networks nanostructures are investigated by scanning electron microscopy(SEM),transmission electron microscopy(TEM),energy dispersive spectrum(EDS),selected area electron diffraction(SAED),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS).The 3D backbone structure and double-metallic property of K2PtC14/K3Co(CN)6 cyanogel are responsible for the 3D structure and the high alloying degree of as-prepared products,respectively.Compared to the pure Pt nanoparticles,3D platinum-cobalt alloy networks nanostructures exhibit superior electrocatalytic activity and stability for methanol oxidation reaction(MOR),which is ascribed to their unique 3D structure and alloy property.