Structure Control And Electrocatalytic Properties Of Bimetallic Nanomaterials

The work of the dissertation was conducted around the design of high efficiency catalysts for the electrochemical energy conversion devices(proton exchange membrane fuel cell and water electrolysis).The alloy,composition segregated structure,and assembly of nanosheets were synthesized according to the strategies for tuning the activities nanocrystalline materials,such as alloy effect,surface control,and interface control.The research contents of the dissertation include the synthesis of Pt-Cd nanocubes,Pt-Cd-M nanocubes,tetrahexahedral Pt-Ni nanocrystals(THH Pt-Ni NCs),rhombic dodecahedral Pt-Ni nanocrystals(RDH Pt-Ni NCs),tetrahexahedral Pt-Ni nanoframes(THH Pt-Ni NFs),rhombic dodecahedral Pt-Ni nanoframes(RDH Pt-Ni NFs),Ru-Ni sandwiched nanoplates and assembly of MoS2 nanosheets with the study of their electrocatalytic performances.The specific research achievements are as follows:(1)The Pt-Cd and Pt-Cd-M(M=Mn,Fe,Co,Ni and Cu)nanocubes were synthesized by using oleyl amine as the solvent and glucose as the reducing agent with the study of their catalytic performances in electrocatalytic oxidation of methanol and formic acid.The results show that Pt6Cd4Co1 NCs/C exhibit the best specific activities and mass activities in catalytic oxidation of methanol,which are 3.43-times and 4.35 times higher than those of the commercial Pt/C,respectively.Furthermore,the stability of the Pt6Cd4Co1 NCs/C is better than those of the Pt3Cd2 NCs/C and Pt/C.In electrocatalytic oxidation of formic acid,different Pt6Cd4M1 NCs/C exhibit higher specific activities and mass activities than those of the Pt/C.(2)The Pt-Ni nanocrystals were synthesized by one-pot method,which use the mixed solution of oleyl amine and oleic acid as the solvent,dodecyl trimethyl ammonium chloride as the surfactant.When the volume ratio of oleyl amine to oleic acid was 2.5/2.5,the tetrahexahedral Pt-Ni nanocrystals were prepared,while the volume ratio of oleyl amine to oleic acid was 4/1,the rhombic dodecahedral Pt-Ni nanocrystals were obtained.Then the tetrahexahedral Pt-Ni nanoframes and rhombic dodecahedral Pt-Ni nanoframes obtained by etching the tetrahexahedral Pt-Ni nanocrystals and rhombic dodecahedral Pt-Ni nanocrystals,respectively,were dispersed onto the active charcoal and their performances in electrocatalytic oxygen reduction and methanol/ethanol oxidation were explored.The experimental results show that the mass activities and specific activities of catalytic oxygen reduction follow the order of THH Pt-Ni NFs/C>RDH Pt-Ni NFs/C>Pt/C.Among them,mass activity and specific activity of the THH Pt-Ni NFs/C are 20.9-times and 25.9-times higher than those of the commercial Pt/C,respectively.Meanwhile,both the THH Pt-Ni NFs/C and RDH Pt-Ni NFs/C exhibit superior performance than commercial Pt/C in the electrocatalytic oxidation of methanol and ethanol.(3)The Ru-Ni sandwiched nanoplates with different compositions were prepared by using benzyl alcohol as the solvent and their catalytic activities of hydrogen evolution,oxygen evolution and water splitting in alkaline solution were explored.The results turn out that the Ru2Ni2 sandwiched nanoplates exhibit the best activities in hydrogen evolution and oxygen evolution.The Tafel slope and overpotential of the Ru2Ni2 sandwiched nanoplates at the current density of 10 mA cm-2 in 1 M KOH are 23.1 mV dec-1 and 40 mV,which are lower than the Tafel slopes and overpotentials of the Pt/C and Ir/C.The overpotential of the Ru2Ni2 sandwiched nanoplates for oxygen evolution at the the current density of 10 mA cm-2 in 1 M KOH is also lower than those of the Pt/C and Ir/C.Then we applied the Ru2Ni2 sandwiched nanoplates in the two-electrode system,whose water splitting activity in 1 M KOH was explored.The results are that the onset potential of water splitting is 1.45 V and the potential increase only 12 mV after electrolysis for 40 h.(4)The assembly of MoS2 nanosheets were synthesized by using wet chemical route and its catalytic activity of electrochemical hydrogen evolution in 0.5 M H2SO4 was studied.The results turn out that the 1-methyl-2-pyrrolidinone as the solvent play a signifancant role in synthesizing the assembly of nanosheets.The assembly of nanosheets exhibit excellent activity of electrochemical hydrogen evolution with onset potential of-0.125 V and Tafel slope of 39 mV dec-1.Meanwhile,they exhibit good stability with no obvious change in the polarization curve after 1000 cyclic voltammetry sweeps.