Structrue-optimized Synthesis Of Metallic Alloy Nanocatalvts And Their Tunning Eletrocatalystic Performances

Human beings are facing the dilemma of energy shortage and environmental pollution since the traditional fossil-fuel-dominated energy models.More and more attention has been paid to seeking alternative sources of new clean energy.Fuel cells,such as proton exchange membrane fuel cell,are considered to be one of the most promising new energy devices.However,before the fuel cells can actually take replace to fossil energy,their cost,performance and longevity are the three most concerned topics.The fuel cell cannot be further commercialized since the shortage of catalysts currently filled in the anode and cathode of fuel cells.It is very important to develop electrocatalysts with higher activity,longer life and lower cost than that of current commercial Pt catalyst.This work is guided by the major issues facing in the current energy and environment.And combining with experiment synthesis,physical characterization and electrochemical characterization methods.We developed a new thought of designing and synthesis of high efficient metallic nano-electrocatalysts.Under the guidance of the thought,we set up a new method for the controlled-synthesis of metallic nanoalloy materials in non-aqueous system.Through the new method,we synthesized a series of new metallic nanoalloys.Main contents are as follows.1.Morphology control synthesis of zero-dimensional Pd-Cu alloyed nanostructures and their electrocatalytic performance.Three different shapes of PdCu alloyed monodisperse nanoparticles(cube,sphere and spherical)are synthesized by simply adjusting the concentration of capping agent via a solvothermal method.The mechanism of shapes control synthesis of PdCu alloyed monodisperse nanoparticles are studied.The electrocatalytic results show that the electrocatalytic properties of PdCu alloy nanoparticles are much dependent on their shape.Among three different shapes,the spherical PdCu alloy nanoparticles showed the best catalytic activity for formic acid oxdation.This work adopts the single type of capping agent to adjust the shape of bimetallic alloy nanoparticles,and further affecting the electrochemical activity.It opens a way for shape controlled synthesis of other alloy nanoparticles and the tuning of catalytic performance.2.Synthesis of zero-dimensional PtNiAg(Cu)with hetero-nanostructure and their electrocatalytic performance.Firstly,AgNi/PtAgNi core/shell nanoparticles are synthesized by a seed-mediated method in the organic phase solution system.The AgNi/PtAgNi nanoparticle is consist of AgNi core and PtAgNi shell.The formation of this unique structure is related to the Galvanic displacement process.Electrochemical test showed that AgNi/PtAgNi nanoparticles showed better electrocatalytic activity and stability than commercial Pt/C.In addition,AgNi/PtAgNi nanoparticles also showed better methanol tolerance than commercial platinum carbon.The above results indicate that core/shell AgNi/PtAgNi nanoparticles have the potential to be a methanol cathode catalyst for direct methanol fuel cell.Secondly,Low Pt-content ternary PtNiCu nanoparticles with accessible surfaces are synthesized by a facile one-pot method.After pickling and heat treatment,the surfaces of nanoparticles are converted into the Pt-enriched surfaces(H-PtNiCu-AAT),which greatly improved the utilization ratio of Pt in the catalytic process.The forming process of the hollow and surface of PtNiCu trimetal nanoparticles is closely related to the concentration difference of the metal cation in the solution,and the intermediate process involves the galvanic substitution reaction.In the whole process,the contents of Pt in the particles were maintained at a low level.Electrocatalytic performance studies show that H-PtNiCu-AAT nanoparticles exhibit excellent multifunctional electrocatalysis of HER/OER/MOR activity and stability.The reason for the excellent performance is their open structure and Pt-enriched surfaces.3.Synthesis of one-dimensional Cu-Pt(Pd)with hetero-nanostructures and their electrocatalytic performance.Firstly,we used Cu nano wire as the crystal seed,and the metal Pt salts are reduced and deposited on the surface of Cu nanowires by seed mediated method.The composite structure(Cu/PtCu NWs)coated with Cu nano wires in the shell layer composed of PtCu alloy nanoparticles was successfully synthesized.In addition,the adjustment of particle components on Cu/PtCu nanowires was realized by adjusting the amount of Pt salt.The influence of different surface components on Cu/PtCu nanowires was studied.Electric catalytic research results show that the Pt and Cu feeding molar ratio of 2:15 sample has the most excellent FAOR performance.The peak potential mass activity and specific activity respectively can reach to 6 times and 6.6 times of platinum carbon.Secondly,we used Cu nanowire as the crystal seed,and the Pd salts are reduced and deposited on the surface of Cu nano wires by seed mediated method.PdCu alloy nanoparticles-decorated Cu nanotubes(Cu/PdCu NTs)are obtained through Galvanic replacement process and the Kirkendal effect.The electrocatalytic results show that the mass activity of Cu/PdCu NTs are 3.4 times of commercial Pd/C for FAOR.DFT calculations are used to explain the excellent performance of Cu/PdCu NTs.Cu/PdCu NTs shows the lowest reaction energy barrier,suggestging its excellent electrocatalytic activity for FAOR.4.Control synthesis of one-dimensional Cu-Ni hetero-nanostructures and their electrocatalytic performance.Cu/NiCu electrocatalysts integrating alloy,core/shell and one-dimensional structures are synthesized ed by a facile one-pot strategy.It is consist of Cu nanowire-core and NiCu shell.Electrocatalytic results show that Cu/NiCu nanowires exhibit good electrocatalytic MOR performance and stability.Furthermore,we also studied the components effect of surface NiCu alloy for MOR.The research indicates that the good MOR performance should be attributed to the structural characteristics of Cu/NiCu nanowires.The Ni-Cu surface alloying structure can effectively change the charge distribution of the atomic configuration,the core-shell structure can be optimized for the use of Ni and Cu and the one-dimensional structure can effectively enhance the charge transfer between the electrode surface and the active sites,making the prepared NWs promising electrocatalysts.All these provide possible ideas for the introduction of non-precious metal catalysts into DMFC.