Electrochemical Synthesis Of Lanthanum-doped Platinum Nanocrystal Catalysts In Deep Eutectic Solvents And Their Electrocatalytic Performance

This thesis put emphasis upon studies of electrochemical shape-controlled synthesis in deep eutectic solvents(DESs)of La-doped Pt nanocrystals(NCs)with high-index facets and high catalytic performance.The subject presents a frontier of multidiscipline covering nanomaterials,electrocatalysis,surface science and energy science(direct ethanol fuel cell,DEFC).We have reported the electrochemical synthesis in deep eutectic solvents(DESs)of concave tetrahexahedral(THH)Pt NCs enclosed by {910} and vicinal high-index facets,which exhibit higher electrocatalytic performance for ethanol oxidation.However,the above concave cubic Pt NCs are too large and their electrocatalytic properties still need to be improved.Therefore,this thesis mainly studies the electrochemical synthesis of rare earth La and La-doped Pt NCs catalysts and their electrocatalytic performance.The main original results are summarized as follows:(1)The olive-like lanthanum particles with uniform size and shape were successfully prepared in choline chloride/urea DESs by electrochemical methods.Scanning electron microscopy(SEM),transmission electron microscopy(TEM)and X-ray photoelectron spectroscopy(XPS)were used to characterize the morphology,size and structure of the prepared samples.At the same time,the effect of temperature,time and precursor concentration on the size and morphology was investigated systematically.The results show that the temperature and precursor concentration of particles in the preparation olive shape play a key role for the preparation of the olive-like lanthanum particles.(2)With the choline chloride/urea DESs as the medium,the concave cube PtLa alloy NCs were electrochemically synthesized by the co-deposition method.Scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray energy dispersive spectroscopy(EDS)and X-ray photoelectron spectroscopy(XPS)were used to characterize the composition,morphology and surface structure of the prepared PtLa alloy NCs.The results show that as-synthesized concave cube PtLa alloy NCs exhibit higher electrocatalytic activity and stability for ethanol oxidation.(3)The La-modified Pt nanocrystal catalyst was successfully prepared by electrochemically modifying rare-earth lanthanum on the surface of concave cube Pt NCs.Scanning electron microscopy(SEM),transmission electron microscopy(TEM)and X-ray photoelectron spectroscopy(XPS)were used to characterize the prepared samples.With ethanol as probe molecules,the electrocatalytic properties of La-modified Pt NCs were evaluated by using cyclic voltammetry(CV)and chronoamperometry methods.It is found that the modification of lanthanum can improve the electrocatalytic performance of Pt NCs catalyst for ethanol oxidation.The results of this thesis can provide a useful reference for the preparation of metal lanthanum with different morphologies under normal temperature conditions.The as-prepared La-doped Pt NCs catalysts show a potential prospect in DEFC and other electrocatalytic application.