Synthesis Of Pt,Rh-Based Tri-Metallic Nanocrystals And Their Electrocatalytic Applications For Fuel Cells

With the rapid development of global economy in the 21st century,energy crisis and environmental pollution are becoming increasingly prominent.Under this background,the development of green new energy and efficient energy conversion devices has become the key to solving the problem.Fuel cell is a kind of energy conversion device which can directly convert the chemical energy in fuel into electrical energy through electrochemical reaction.It has great application prospects in portable power supply,power supply,fixed power station and other fields.On the one hand,hydrogen energy is the most ideal fuel for fuel cells,with the advantages of high energy density,clean products and no pollution.Therefore,the electrolytic water technology composed of hydrogen evolution reaction?HER?and oxygen evolution reaction?OER?is considered as one of the efficient hydrogen production routes.On the other hand,direct methanol fuel cells?DMFCs?,which have the advantages of high energy density,environmental friendliness and convenient storage of liquid fuel,are widely concerned and become an important part of the new energy system.At present,how to cleanly and efficiently produce hydrogen on a large scale and greatly improve the performance of DMFCs is the key to promote the commercialization of fuel cells,especially the development of high-performance catalysts.Among them,precious metal nanocrystals?such as Pt,Rh,Ir,etc.?are the best catalysts in fuel cell-related electrode reactions.However,its limited reserves and high costs directly hinder the development of fuel cells.This paper focuses on the rational design of nanocrystals,realizes the controllable synthesis of Pt,Rh-based ternary alloys and core-shell nanocrystals,and studies their electrocatalytic properties.The following results have been achieved:?1?Using Au nanoparticles as seeds,Au@Rh Cu core-shell dendritic nanocrystals were prepared by a seed-mediated approach.Au@Rh Cu exhibited excellent catalytic activity toward HER and OER.Among them,Au@Rh₃Cu obtains the smallest overpotential and the lowest tafel slope when the current density is 10 m A/cm².The increased catalytic activity can be assigned to the lattice strain induced by the core-shell nanostructure and the synergistic effect between metal elements.?2?Pt Rh Cu ternary alloy dendritic nanocrystals were prepared by a facile one-pot approach and applied to methanol oxidation reaction?MOR?.This kind of dendritic structure has a large specific surface area and can expose a wealth of active sites.Compared with other dendritic nanocrystals,Pt₄₇Rh₈Cu₄₅catalyst showed the best specific activity and mass activity toward MOR,which were 5.8 and 2.9 times that of commercial Pt/C,respectively.The lattice compression effect caused by alloying of the three elements is beneficial to the regulation of the electronic structure of Pt,thereby enhancing the intrinsic MOR activity of Pt.At the same time,in the process of catalytic methanol oxidation,the synergistic catalytic effect can improve the anti-poisoning ability of the catalyst.?3?Using Au decahedron as seeds,Au@Pt Cu nanostars with abundant surface defects were prepared by a seed-mediated approach and applied to methanol oxidation reaction?MOR?.Through composition optimization,Au@Pt_1.2Cu nanostars achieved the highest specific and mass activities for MOR,which were about 5.9 and 1.6 times higher than those of commercial Pt/C,respectively.This enhanced electrocatalytic performance may be attributed to the unique twin structure and the synergistic effect between Pt and Cu components.