Research On Controllable Synthesis Of Alloy Nanomaterials And In-situ TEM Observation Of Solid-liquid Interface

Due to the unique physical and chemical properties,nanomaterials are the research hotpots in many fields such as materials,physics,chemistry,biology and some intercross subjects.The exploration of the corresponding nano-technologies has great potential in many fields,and it can promote the future scientific and technological progress as well as the economic effect.The controllable synthesis of supported alloy nanomaterials,unsupported hollowed alloy nanomaterials and dynamic imaging of crystal growth in solution by in-situ transmission electron microscopy(in-situ TEM)are very important for nanomaterials research field.The main results are summarized below:1.Conversion of the ethanol to CO2 at low potential through C-C bond cleavage is vital for the utilization of ethanol in direct ethanol fuel cells.The addition of Rh into Pt lattice is considered as an efficient route for improving of the CO2 selectivity during ethanol electro-oxidation.PtRh alloy nanoparticles with different element ratios supported on reduced graphene oxide(RGO)were synthesized.Among them,PtiRhi/RGO shows an ultrahigh mass activity of 0.285 A mgpt-1 at 0.4 V(vs.SCE),2.48 times as high as the commercial Pt/C.Results of high-resolution transmission electron microscopy(HRTEM)reveal that the supported Pt1Rh1 alloy nanoparticles are in cubic shape with rough surface and high-density of step sites.Results of in-situ FTIR spectroscopy indicate that the addition of Rh greatly alleviates the COad poisoning on Pt surface.CO2 was generated at a low potential of-0.10 V,and the CO2 selectivity is 16.2 times as high as that of commercial Pt/C at 0.40 V.In-situ FTIR spectroscopy using isotopically-labeled ethanol further confirm the superior CO2 selectivity on Pt1Rh1/RGO under low potentials is derived from the addition of Rh and high-density of step sites,which facilitates the C-C bond cleavage and the oxidation of alcoholic groups.And the generated CO under low potentials is adsorbed on Pt sites.2.Controlling the size,morphology and crystal structures of metal nanoparticles are of great importance for many applications,such as plasmonics,electronics,and catalysis et al.Achieving mastery over the synthesis of hollowed metal nanomaterials has emerged as one of the most important research hotspot in the last few years.Herein,we demonstrate a refined pathway for controllable synthesis nanomaterials in different morphologies and structures using template synthesis method by tuning the deposition,diffusion and galvanic replacement reaction speed.Palladium metal precursor through galvanic replacement reaction on the order of edges,corner sites and faces of Ag nanocubes.The result suggests that after tuning the synthesis conditions we can get PdAg alloy nanoframe,nanobox and nanocage with different pore sizes.More interesting,all these nanomaterials can be single crystalline or polycrystalline,which can be tuned by the reaction speeds of deposition,diffusion and galvanic replacement.The shell thichness of the single crystal surfaces is measured to be sub-nanometer.Templates in different size with different shapes are also being studied and show similar regularity.Our results reported herein offer a refined pathway for directing synthesize materials with hollowed nanostructure and different morphologies,which is of great significance in controllable synthesis of hollow nanomaterials.3.The solid-liquid interface is of great importance for both fundamental research and industry application,but interface structure is not well known yet at molecular level,because of the limitation of the characterization methods.Here,the metal-water interface was directly imaged by in-situ liquid cell transmission electron microscope at atomic scale resolution.An unexpected new phase with concentrated metal ions was found between metal surface and bulk water.The interphase with a thickness of 1-4 nanometer sticks on the metal surface during mass transportation between metal and bulk solution.DFT simulation indicates the charges play a role in the existence of stable interphase.Such a new interphase may play a vital role in the catalysis and metal corrosion,which may also provide new insight for the fundamental understanding of the solid liquid interface.