Controllable Synthesis and Their Electrocatalytic Application of Platinum Based Nanostructures
Author:Wu Feng Xia
Supervisor:xu guo bao
As electrocatalysts in fuel cells,noble metal based nanocrystals are usually employed to catalyze the oxidation reactions to overcome the slow electrode reaction kinetics of the fuel molecules and realize the power output of full cells.However,the low reserve in nature and high cost of noble metals greatly hinder the commercialization of full cells.Thus,improving the performance of full-cell electrocatalysts and minimizing the usage of noble metals has become an important subject of the current research.Over the past decades,controllable synthesis of noble metal based nanomaterials has attracted wide attention and much progress has been made.In this thesis,we focus on the rational engineering the surface and interface of noble metal-based nanomaterials and related electrocatalytic applications.The main achievements are outlined as follows:(1)Hierarchical concave layered triangular PtCu alloy nanostructures(HCLT)were successfully synthesized by a one-pot hydrothermal method using carnitine.The concavity/convexity and the number of layers of PtCu HCLT nanostructures could be fine-tunable by controlling experiment conditions.The concave surfaces,interconnected dendritic structure,abundant edge and corner atoms in the branch of nanocatalysts provide lots of easily accessible active sites and high conductivity,and thus make PtCu nanostructures exhibiting excellent formic acid electrocatalytic activity and stability.(2)We have further synthesized PtCu excavated octahedral nanostructures built from nanodendrites(EONDs).Meantime,Cu in the alloyed nanostructures shows metallic and oxidation states(Cu(0):Cu(Ⅱ)=1:2.2)because of the rich Cu composition(Pt:Cu=1:2.68).The nanostructures possess abundant edges and corner atoms in the branches and three-dimensional open nanostructure,which provide more active sites and fast proton transport.The oxidized form of copper promotes water decomposition under alkaline conditions.Due to these advantages,PtCu-O EONDs exhibit high alcohol electrocatalytic performance and anti-piosioning activity in analkaline solution.(3)According to the literature,two-dimensional ultrathin nanosheets can greatly improve the utilization of Pt metal.Therefore,based on our previous work,we further synthesized highly excavated octahedral nanostructures integrated from ultrathin mesoporous PtCu3 nanosheets(EOUM).In addition,the PtCu3 EOUM nanostructure possess Cu-rich surface.Besides the highly mesoporous features,3D open surfaces,and ultrathin nanosheets,the Cu rich environment of PtCu3 alloy can enhance the OH-adsorption and weaken CO adsorption,facilitating the oxidative removal of COads,and thus leading to dramatically enhanced MOR performance.(4)We further synthesized PtNi multicube nanoarchitectonics enriched with Ni(68%)based on the direct nucleation followed by the epitaxial growth.This attributes the spontaneous isolation among nucleation and growth step.Ni exists in PtNi multicube in the form of metallic state.These structural and compositional merits enhanced the MOR and EOR mass activity of PtNi multiube by 2 and 7 times,respectively compared to Pt/C catalyst along with a superior CO tolerance.