Ionic Liquid-Assisted Synthesis Of Noble Metal(Au?Pd) Nanoclusters And Their Catalytic Properties On Formaldehyde Oxidation Reaction

Noble metal nanoclusters?MNCs?have ever received intensive attention in a wide range of applications in optics,electronics,magnetism,biology,catalysis,etc,owing to their unique atomic and electronic structures,excellent optical,electrical and catalytic properties.In particular,because of the ultra-small size of nanoclusters and the resulting quantum confinement effect,such nanoclusters exhibit discrete,molecular-like electronic structure,which are fundamentally different to the small molecules?e.g.organometallic compound?and nanoparticles?>2 nm?.Among them,gold?Au?nanoclusters and palladium?Pd?nanoclusters with excellent catalytic properties have attracted researcher's extensive attention.Based on the previous research work,green and environmentally friendly nobel metal nanoclusters with excellent performance were prepared with the assistance of the unique properties of the amino functionalized ionic liquid?IL-NH₂?.Meanwhile,the UV-Vis spectroscopy,Transmission electron microscopy,X-ray photoelectron spectroscopy,X-ray diffraction and Electrochemical workstation were used to characterize the samples.This work mainly includes the following contents:1.AuNCs@IL nanoparticles were successfully prepared by using amino-functionalized ionic liquid as ligand and sodium borohydride as reductant in the mixed solution of water and methanol.The nanoclusters were synthesized by the monolayer protecting method,and then characterized and analyzed by TEM and UV-Vis.Various factors influencing the nanoclusters size of AuNCs@IL such as the ratio of raw materials,catalyst amount,the system ratio of reaction solution,temperature and pH were systematically investigated to control the structural of AuNCs@IL nanoparticles.AuNCs@IL nanoparticles prepared by this method were uniform and the average particle size was about 1-2 nm.In order to verify the feasibility of the method,three different noble metals?Au,Ag,Pt?with controllable size 1-2 nm were tested with thiol-functionalized ionic liquid instead of amino-functionalized ionic liquid,which verified the universality of the experimental method.2.The synthesis followed the same protocol as that for PdNCs@IL nanoparticles besides the ionic liquid,and characterized by TEM,UV-Vis,XPS,XRD.We loaded the PdNCs@IL on the carbon substrates for evaluating their performance in catalyzing formaldehyde oxidation reaction?FOR?and benchmarked against that of commercial Pd/C catalyst.At the same time,we have determined the electrochemically active surface areas?ECSAs?,CO stripping voltammetry,area activity,mass activity and electronic effects to analyse reaction to verify the enhanced catalytic performance of PdNcs@IL nanoparticles for formaldehyde oxidation.The electrochemical measurements prove that the ionic liquid-assisted Pd nanoclusters have mass-normalized activity approximately 7 times than that of commercial Pd/C catalysts for the oxidation of formaldehyde.The current density of PdNCs@IL/C decays slowly and is higher than that of commercial Pd/C after 7200 s,which to evaluate the long-term stability of the PdNCs@IL/C and Pd/C catalysts for FOR.All of these might be due to the effectiveness of interaction between the,IL layer immobilized on the Pd nanoclusters and their tiny sizes,thus improving the catalytic activity.