Amine-based Small Molecule-assisted Synthesis Of Pt-based Catalysts And Their Catalytic Performance For Methanol Oxidation

Due to energy shortage and environmental pollution,fuel cells have received widespread attention as an energy conversion device with low pollution,high energy conversion efficiency,and high energy density.The precious metal platinum is the most effective catalyst for fuel cells,but its small reserves,high price and poor catalytic stability have hindered the commercial development of fuel cells.Therefore,there is an urgent need to develop a new kind of inexpensive and highly active platinum-based catalysts.Synthesizing electrocatalysts with special morphologies and components to maximize the utilization of Pt is current research hotspots,which can reduce the research cost and improve the catalytic activity and stability of platinum-based catalysts.In this thesis,using N,N'-methylenebisacrylamide as the morphology directing agent,we designed three different platinum-based catalysts with special morphologies by simple one-pot hydrothermal method,and studied their catalytic performance for methanol oxidation reaction.The specific research results of this thesis are as follows:1.The hollow porous Pt nanobowls with fully open internal and external surfaces were successfully synthesized with N,N'-Methylenebisacrylamide as the morphology directing agent,H₂PtCl₆ as metal precursor and Formaldehyde as reducing agent by one-pot hydrothermal method.Studies have shown that the obtained Pt nanobowls are self-assembled from Pt particles of 4 nm.Compared to commercial Pt black,the hollow porous Pt nanobowls exhibit excellent catalytic performance for methanol oxidation reaction.The mass peak current density is 507.8 m A mg _Pt^-1,which is 2.10 times that of commercial Pt black(242.7 m A mg _Pt^-1),the electrochemical active area(ECSA)is 18.2m² g^-1,which is 1.46 times that of the commercial Pt black catalyst(12.5 m² g^-1).The hollow porous Pt nanobowl has better anti-toxicity ability compared with commercial Pt black,the intial oxidation potential and oxidation peak potential of Pt nanobowl are negatively shifted by 140 m V and 110 m V,respectively.The excellent catalytic performance of the hollow porous Pt nanobowls can be attributed to the fully open inner and outer surfaces,the larger specific area providing more active sites for the catalytic process and the self-assembled structure of ultrasmall nanoparticles improving the utilization of Pt atoms.2.The hollow porous double shelled Pt₃Ag₁nanocages were successfully synthesized with N,N'-Methylenebisacrylamide as the morphology directing agent,H₂PtCl₆ and AgNO₃as metal precursors and ascorbic acid as reducing agent by one-pot hydrothermal method.Studies have shown that the surface of the Pt₃Ag₁ catalyst is rich in defects and has a stable structure with inner and outer double shells.Compared to commercial Pt black,the hollow porous double shelled Pt₃Ag₁nanocages exhibit excellent catalytic performance for methanol oxidation reaction.The mass peak current density is 566.8 m A mg _Pt^-1,which is 2.20 times that of commercial Pt black,the electrochemical active area(ECSA)is 17.8 m² g^-1,which is 1.36 times that of the commercial Pt black catalyst.The hollow porous Pt₃Ag₁nanocages has better anti-toxicity ability compared with commercial Pt black,the intial oxidation potential and oxidation peak potential of Pt₃Ag₁nanocages are negatively shifted by 50 m V and 30m V,respectively.The excellent catalytic performance of the hollow porous Pt₃Ag₁nanocages can be attributed to the double-shell structure effectively improving the utilization efficiency of Pt atoms and the porous structure accelerates the transport of mass and electrons during catalytic process.Density functional theory(DFT)demonstrated that the Ag doping facilitates chemical desorption of intermediate CO_adsduring catalystic process,releasing more Pt active sites,which is beneficial to improve the MOR catalytic performance.3.The three-dimensional Pt₁Ag₁ nano coral-like dendrites were successfully synthesized with N,N'-Methylenebisacrylamide as the morphology directing agent,H₂PtCl₆ and AgNO₃as metal precursors and hydrazine hydrate as reducing agent by one-pot hydrothermal method.Studies have shown that the Pt₁Ag₁ has a rough surface and a stable three-dimensional dendritic structure.Compared to commercial Pt black,the three-dimensional Pt₁Ag₁ nanocoral-like dendrites exhibit excellent catalytic performance for methanol oxidation reaction.The mass peak current density is 580.4m A mg _Pt^-1,which is 2.70 times that of commercial Pt black,the electrochemical active area(ECSA)is 19.3 m² g^-1,which is 1.16 times that of the commercial Pt black catalyst.The excellent catalytic performance of the three-dimensional Pt₁Ag₁ nanocoral-like dendrites can be attributed to the three-dimensional coral-like dendritic structure has a larger electrocatalytic activity area,which can provide more active sites for the catalytic process.The introduction of Ag to form PtAg alloy structure can adjust the electronic structure of Pt and improve the utilization of Pt atoms,which is beneficial to transport of electrons during catalytic process.