Phase And Interface Control Of Platinum-Based Nanomaterials And Their Catalytic Performances

As an important member in the field of materials science,noble metal nanomaterials not only possess outstanding physical,chemical and catalytic properties of precious metals,but also have the features of large specific surface area,high surface atom occupation and high surface energy of nanomaterials.Thus,the precious metal nanomaterials have wild applications and practical values in the fields of optoelectronics,biology,energy,catalysis and et al.Among the precious metal nanomaterials,platinum(Pt)-based nanomaterials have stood out and attracted great attention and extensive research from scientific researchers due to their unique catalytic performance and good chemical stability.Typically,the catalytic properties of Pt-based nanomaterials are related to their structure.Therefore,rationally controlling the structure of Pt-based nanomaterials and clarifying the relationship between their structure and catalytic performance are significant for their performance improvement.Currently,researchers have conducted substantial studies on the size,morphology,and composition control of Pt-based nanomaterials and achieved many research results.However,with the increasing performance requirement of Pt-based nanomaterials in catalysis,the catalytic performance of Pt-based nanomaterials is difficult to further improve under the only control of catalysts’ size,morphology and composition.Therefore,developing new control strategies of Pt-based nanomaterials structure(such as phase and interface control)to further improve the catalytic performance of Pt-based nanomaterials is the research hotspot of Pt-based nanomaterials and needs to be urgently solved.Herein,our doctoral dissertation mainly focuses on the phase and interface control of Pt-based nanomaterials.Through the heat treatment or wet-chemical synthesis,a series of Pt-based nanomaterials with uniform size,novel structure,and unique interfaces have been constructed.We carried out detailed characterization of the synthesized Pt-based nanomaterials.Particularly,we deeply analysized the interface structure and revealed its formation mechanism.Furthermore,we systematically evaluated the catalytic performance of the synthesized materials in the hydrogen evolution reaction and selective hydrogenation.Based on the theoretical calculations and X-ray spectroscopy,we revealed the relationship between the interfaces and catalytic performance.The main research content and conclusions are summarized as follows:Chapter 1.We introduced the research background of noble metal nanomaterials in brief,and summarized the recent progresses in the properties,structural control,and catalytic applications of Pt-based nanomaterials.Based on this,we proposed the topic basis and main research project for our doctoral dissertation.Chapter 2.We created a phase-and interface-engineered Pt-Ni NWs/C-air catalysts with Pt3Ni/NiOx interfaces by simple thermal annealing of the highly composition-segregated Pt-Ni NWs/C in air.Through changing the Ni/Pt ratio in origin Pt-Ni NWs/C,the density of NiOx/Pt3Ni interfaces in Pt-Ni NWs/C-air can be readily controlled.Benefitting from the unique 1D structure,controlled interfaces and phases between the Pt3Ni and NiOx,the Pt-Ni NWs/C-air exhibits promising activity for alkaline HER.This study provides a surface and phase-engineering strategy for designing unique catalysts with excellent electrocatalytic performance for HER and beyond.Chapter 3.We report an efficient wet-chemical approach to construct one-dimensional metal/sulfide heterostructures(Pt-Ni NWs-S/C)by directly sulfuring highly composition-segregated platinumnickel nanowires.Through changing the Ni/Pt ratio in origin Pt-Ni NWs/C,the density of NiS/Pt3Ni interfaces in Pt-Ni NWs/C-air can be readily controlled.The Pt3Ni/NiS hetero structures display enhanced HER activity in alkaline conditions.Specially,the optimized Pt3Ni2 NWs-S/C yield the highest activity in the alkaline condition.The density functional theory(DFT)calculations reveal that the synergy between NiS and Pt3Ni enhances the alkaline HER activity with NiS promoting water dissociation,whereas Pt3Ni recombining Hads to H2.The unprecedented catalytic performance offered by the novel Pt3Ni/NiS heterostructures highlights the importance of interfacial engineering in multicomponent electrocatalysts.Chapter 4.We propose a strategy to modify P into Ni-segregated Pt2Ni3 NWs,where the evolved Ni(OH)x from the segregated Ni could boost the water dissociation during the catalysis and the modified P with high oxophilicity on the surface could sever as OH-anchoring sites,collectively improving the HER kinetics via a synergetic cascade route.As a consequence,the optimal P modified Pt2Ni3 NWs(denoted as Pt2Ni3-P NWs)display an enhanced activity for alkaline HER,which is substantially better than commercial Pt/C and Pt2Ni3 NWs,and surpass most reported Pt-based catalysts.Furthermore,it also shows good stability with limited overpotential decay after 18 h long-term test.This study is help for the rational regulating the surface or interface structure of Pt-based nanomaterials to control the activation and adsorption/desorption of reactants and intermediates in catalysis,and thus improving the catalytic performance.Chapter 5.We have successfully constructed a new class of 1D NixM(OH)2(M=Mn,Fe,Co,Cu,and Al)membranes coated Pt3Ni NWs by using Pt3Ni NWs as growth template,which is the first report of fine engineering of 1D metal NWs@hydroxide membranes composite.Moverover,the coverages and compositions of the NixM(OH)2 membranes could be readily tuned by tuning the amount of the different metal precursors.The optimal synthesis conditions and growth mechanism of Pt3Ni NWs@NiMx(OH)2 NWs coating reaction were also deeply discussed.Compared to the pristine Pt3Ni NWs and Pt3Ni NWs on Ni(OH)2 membranes,the optimized Ni32Cu(OH)2 membranes coated Pt3Ni NWs show enhanced selectivity for hydrogenation of cinnamaldehyde to valuable hydrocinnamaldehyde instead of hydrocinnamyl alcohol.Such enhanced selectivity of Ni32Cu(OH)2 is largely ascribed to the confinement and poisoning effects of the coated Ni32Cu(OH)2 membranes as well as the enhanced interactions between the Pt3Ni NWs and Ni32Cu(OH)2 membranes.This study demonstrated the effect of dimension and interface control on catalytic performance,providing a research basis for the design of multifunctional and high-performance Pt-based nanomaterials with multiple structure control.