Synthesis Of Platinum/Ruthenium-Based Nanomaterials And Exploration Of Their Electrochemical Properties

Metal nanomaterials have been widely used in the medical industry,chemical industry,environmental governance and fuel cells.In particular,noble metal nanomaterials have been extensively studied because of their extremely excellent performance in various fields.However,the high price and scarce reserves of precious metals severely limit their practical application in various fields.Therefore,the efficient use of precious metal nanomaterials has become a top priority.Many studies have shown that the properties of nanomaterials are closely related to their size,structural composition and crystal plane exposure.Therefore,the precise control of the size,morphology and structural composition of precious metal nanomaterials is an effective strategy to solve the efficient use of precious metal nanomaterials.In this thesis,the strategy of precisely adjusting the size,morphology and structural composition of precious metal nanomaterials is used to synthesize electrocatalysts with high performance and the catalytic mechanism is studied in depth through density functional theory.The core content of this work can be summarized into the following aspects:1.Ce oxygen species are anchored on Pt nanoparticles(NPs)to improve methanol oxidation reaction performance(MOR).Here we synthesized a Cemodified Pt NP with Cerium(?)oxygenated species(1 wt%Ce content)anchored on Pt NPs.High-angle annular dark field-scanning transmission electron microscopy,X-ray photoelectron spectroscopy and X-ray absorption fine structure spectroscopy were combined to characterize this special structure.In terms of performance,the MOR performance of the synthesized Ce-modified Pt nanoparticle catalyst in acidic and basic media reached 1.47 mA/?g-Pt and 8.67 mA/?g-Pt,respectively,which was significantly better than Pt NPs and commercial Pt/C,commercial PtRu/C,and most Pt-based electrocatalysts reported in recent literature.Through density functional theory(DFT)calculation analysis,we found that the introduction of Ce oxygen species would lead to a decrease in the MOR initial potential of the Pt nanoparticles and significantly enhance the binding energy of OH*to promote the removal of CO*in the potential determining step.This work provides an effective strategy for the development of efficient Pt-based electrocatalysts.2.Ru1Ptn single-atom alloy(SAA)acts as a dual-function catalyst to promote the performance of MOR and hydrogenation reaction(HOR).In this chapter,we used hydrogen and nitrate ions to precisely adjust the reducing ability of Pt precursors and Ru precursors,so that Ru atoms entered into Pt nanocrystals in the form of single atoms.Through High-angle annular dark field-scanning transmission electron microscopy,X-ray photoelectron spectroscopy and X-ray absorption fine structure spectroscopy characterization,we proved that Ru existed in the form of single atoms in Ru1Ptn SAA catalysts.Impressively,the Ru1Ptn-SAA exhibited an excellent specific activity(23.59 mA cm-2)and mass activity(2.996 mA/?g-Pt)for MOR,and excellent exchange current density activity(1.992 mA cm-2)and mass activity(5.03 mA/?g-Pt)for HOR.Density functional theory calculations revealed that the introduction of Ru atoms greatly reduced the reaction energy barrier for the decomposition of water molecules,which promoted the removal of CO*in the MOR process,and adjusted the Gibbs free energy of hydrogen adsorption to promote the HOR.The research in this chapter proves that precisely adjusting the structure of nanocrystals at the atomic level is a very effective way to develop highperformance catalysts.3.Ar/H₂/O₂ controlled the growth mechanism to synthesize zero,one and two-dimensional Ru nanocrystals and used in acidic electrolyzed water reaction.Herein,we developed a small molecule gas(Ar/H₂/O₂)control strategy to synthesize free-standing 0D Ru nanoparticles,1D Ru nanowires and 2D Ru nanosheets through in-situ regulated the growth dynamics of Ru nanocrystals.A series of physiochemical characterization showed that the growth process of Ru nanoparticles,nanowires and nanosheets followed non-directional growth,shape-directed nanoparticle attachment and directional growth mechanisms,respectively.The kinetic analysis and theoretical calculation results showed that small molecular gas could effectively adjust the reduction rate of Ru precursor and the Gibbs surface free energy of different crystal faces of Ru nanocrystals,which played a key role in the formation process of Ru nanocrystals.Impressively,Ru nanowires and nanosheets,and their respective oxide derivatives exhibited excellent acidic hydrogen and oxygen evolution reaction activities,respectively.Meanwhile,they also exhibited excellent acidic water splitting performance.This work had systematically studied the influence of the small molecule gas on the formation process of Ru nanocrystals,and provided an effective idea for the development and research of high-performance nanomaterials in the future.