LSPR Effect Driven Controllable Synthesis Of Noble Metal Based One-Dimensional Nanostructure And The Electrocatalytic Property

One-dimensional noble metal materials have important applications in electrocatalytic reactions.It is of great significance to develop simple,green and controllable preparation methods.The photochemical method driven by the local surface plasmon resonance（LSPR）effect has attracted more and more attention due to its outstanding advantages of room temperature reaction,simple conditions and multi-dimensional control.Up to date,however,this method is mainly limited to Ag and Au elements,and it is difficult to synthesize one-dimensional noble metal nanomaterials due to uncontrollable nucleation and growth.To address the above challenges,we proposed some new strategies to control the LSPR effect during the nucleation and growth of noble metals and prepared one-dimensional noble metal composite nanostructures with different elements.The electrocatalytic performance of one-dimensional nanomaterials for hydrogen evolution reaction（HER）and methanol oxidation reaction（MOR）were also studied.The structure-activity relationship in electrocatalysis was also studied.The content of this thesis is as follows:（1）One-dimensional Au/Pt wormlike heterostructure nanorods（HSNRs）were synthesized via the LSPR effect.An"illuminate-dark"photochemical reaction strategy was proposed to control the length of the nanostructure by controlling the nucleation process of the photochemical reaction and the growth in the dark reaction.The Au/Pt HSNRs provided an axial channel for electron oscillations which resulted a new absorption peak appeared at 600-1300 nm in the UV-vis spectra.The electrocatalytic HER test results showed that the mass activity normalized by Pt of the optimized Au₅Pt₁ HSNRs at–0.05 V was 23.9 and 10.9 times that of the 20 wt%Pt/C and Au₅Pt₁ NPs,respectively.The optimized Au₅Pt₁ HSNRs had the maximum ECSA and the minimum charge transfer resistance and Tafel slope,thanks to the modulation of electronic structure.（2）A liquid photo-welding method was developed to prepare one-dimensional bimetallic nanochain heterostructures.The strategy of"arrange first and weld later"was proposed.In this process,Au NPs were firstly self-assembled into lines by adding additives,and then were welded by the second metal which was reduced by the LSPR effect of Au NPs.This method can be extended to the photo-welding of Au NPs-Ag and Au NRs.In electrocatalytic HERs,the welded one-dimensional Au₅Pt₁NCs has excellent electronic conductivity and abundant active sites,resulting in smaller Tafel slope,impedance and larger ECSA.The mass activity of Au₅Pt₁ NCs was 4.8 and 10.4 times that of Au₅Pt₁ NPs and commercial 20 wt%Pt/C catalysts,respectively.（3）One-dimensional nanostructures of Au Pt-M ternary noble metals were prepared by photochemical method,and their electrocatalytic MOR properties were studied.Under the irradiation of light source with wavelength≥400 nm,the third element precursor was reduced and deposited to form Au₁₀Pt₁-M ternary structure.The results showed that Pd,Ag and Ni elements can be successfully deposited on the wormlike rod heterostructure of Au₁₀Pt₁.The peak mass activity of Au₁₀Pt₁Pd₁composite in MOR was 6.55 A mg^-1_（Pt/Pd）,which was 14.9,24.3 and 9.2 times of Pt/C(0.44 A mg^-1_（Pt）),Pd/C(0.27 A mg^-1_（Pd）)and Au₁₀Pt₁(0.71 A mg^-1_（Pt）),respectively.Meanwhile,the Au₁₀Pt₁Pd₁ had the lowest initial potential and the highest peak current density,and showed good resistance to poisoning.The addition of Pd element can optimize the composition effect and electronic structure effect of composites,and promote the performance in electrocatalytic MOR.（4）Au₁₀Pt₁ HSNRs was loaded on two-dimensional Mn O₂ to form Au Pt@Mn O₂composite.It was found that the amount of KMn O₄ and reaction temperature had important effects on the formation of Mn O₂.Adding appropriate amount of KMn O₄at 45°C could obtain a well-grown two-dimensional Mn O₂ nanosheet structure.The Au₁₀Pt₁@Mn O₂-M composite had excellent performance in MOR.The peak mass activity(15.52 A mg^-1_（Pt）)of Au₁₀Pt₁@Mn O₂-M was 35.3,57.5 and 21.9 times higher than that of Pt/C(0.44 A mg^-1_（Pt）),Pd/C(0.27 A mg^-1_（Pd）)and Au₁₀Pt₁(0.71 A mg^-1_（Pt）),respectively.At the same time,Au₁₀Pt₁@Mn O₂-M composite had the lowest onset potential,the highest peak current density,and good resistance to poisoning due to the oxidation capacity of Mn O₂ nanosheet,electronic conductivity and interaction with Au₁₀Pt₁ HSNRs.（5）In addition,the size of nanoparticles in LSPR effect driven photodeposition has also been explored.Firstly,Au@Mn O₂ nanosheets were prepared by wet chemical method.Then illuminated to stimulate the LSPR effect of Au NPs to reduce the Pt precursors to Pt NPs and dispersed on Mn O₂ nanosheets which provided a transfer channel for thermal electrons.By changing the light source,the deposition reaction can be adjusted to control the size of Pt NPs.This method can also be extended to prepare Ag/Au@Mn O₂ composite with controllable size of Ag NPs.In HER applications,Pt-520/Au@Mn O₂ had the lowest onset overpotential,and the mass activity of Pt at–50 m V overpotential was 12.9 times and 2.9 times higher than that of commercial Pt/C(1.33 A mg^-1)and Pt-400/Au@Mn O₂(5.8 A mg^-1),respectively.