Research On Electronic Structure Regulation And Electrochemistry Of Pt/Pd-Based Catalysts

Direct liquid fuel cells（DLFCs）have become one of the most promising power generation technologies owing to the high safety,high efficiency,energy conservation and environmental friendliness.At present,one of the main factors hindering the development of DLFCs is the lack of electrocatalysts with low cost,high efficiency and stability.As a kind of commonly used DLFCs electrocatalyst,Pt/Pd based noble metal catalysts have received extensive attention attributed to high catalytic activity.However,the low reserves of Pt/Pd in nature lead to its high price and increased production cost.On the other hand,Pt/Pd based noble metallic nano catalysts are prone to be poisoned by the oxidation intermediates of small molecular fuels during catalytic process,resulting in poor stability and low catalytic efficiency of the whole catalysts.These factors greatly limit the commercialization and further development of DLFCs.Therefore,this paper focuses on how to design and develop novel DLFCs electrocatalysts with low cost,stability,high catalytic activity and strong anti-poisoning ability.This work realizes the regulation of the electronic structure of Pt/Pd-based precious metals through structural design,lattice expansion and disordered arrangement of amorphous atomic structure.The relevant research provides a new idea and choice for the design of efficient DLFCs electrocatalysts.Firstly,in view of the high price of Pt based catalyst,low catalytic activity of methanol under alkaline conditions and poor stability for long-term operation,this paper uses structural design to optimize the catalytic activity of PtCo bimetallic nanocrystals.PtCo bimetallic hollow nanospheres were prepared by template method.On this basis,PtCo nanochains with one-dimensional hollow structure were synthesized.The hollow structure of the catalyst can significantly reduce the usage of noble metals,reduce the cost,effectively increase the specific surface area of the catalyst and expose more active sites,thus improving the catalytic activity of the catalyst eventually.Moreover,one-dimensional linear structure can improve the mass transfer process during catalytic reaction,inhibit the agglomeration of nanoparticles and improve the stability of catalysts.Electrochemical tests reveal that compared with commercial Pt/C catalysts,the methanol catalytic activity of one-dimensional hollow PtCo nanochains increased three times and exhibited superior cycle stability.Experimental results demonstrate that the one-dimensional linear structure of PtCo nanochains can optimize the mass transfer process of methanol oxidation.Besides,the lattice defects at the interface can provide abundant catalytic sites with high activity,optimize the electronic structure of Pt,thus boosting the performance of the catalyst.Introducing lattice expansion into Pt/Pd based catalysts is an effective strategy to improve catalyst performance.However,the introduction of lattice expansion through alloying normally leads to the dissolution of transition metal elements during the long-term operation of the catalysts,contributing to the destruction of the overall structure of the catalysts eventually.To solve this problem,utilizing the characteristic that precious metal Pd can absorb hydrogen and form Pd H phase in hydrogen atmosphere,this paper realized the regulation of the electronic structure of Pd by H,and successfully prepared Pd H_0.43 catalyst.Besides,a layer of amorphous Cu O was wrapped on Pd H_0.43surface with hydrothermal method to maintain the structure stability of the catalyst.The electronic structure of Pd was adjusted by H,enhancing the catalytic activity,stability and anti-poisoning abilities.Electrochemical characterizations suggest that the synthesized Pd H_0.43@Cu O not only exhibits favorable electrochemical performance of methanol oxidation and ethanol oxidation,but also excellent oxygen reduction ability.The bifunctional catalytic properties of Pd H_0.43@Cu O manifest that it can be used as cathode and anode catalytic materials of DLFCs simultaneously.This work provides a new design concept and idea for the development of highly stable and bifunctional DFLCs catalysts.Almost all the reported Pt/Pd based DLFCs catalysts are crystals,which usually encounters the poisoning of catalysts during the electrocatalytic process.Herein,we report a novel amorphous PdNiCuP nanocatalyst synthesized with laser liquid ablation,optimizing the electronic structure of Pd and improve its anti-poisoning ability by taking advantages of the disordered arrangement of atoms in the amorphous structure.Through a series of characterization,it is found that the amorphous catalyst owns typical amorphous structure characteristics,which can effectively regulate the electronic structure of active sites and improve the poisoning problem of crystalline catalysts.The electrocatalytic performance of the amorphous catalyst towards methanol and formic acid oxidation were investigated by electrochemical measurements.The results display that compared with commercial Pd/C,the as-synthesized amorphous catalyst exhibits superior catalytic activity and exceptional stability.Moreover,CO stripping experiments show that amorphous PdNiCuP catalyst will not absorb CO,indicating the superb CO anti-poisoning ability.This work provides insight for the design of DLFCs catalysts with long life and high anti-poisoning ability.This work shows that the electronic structure of Pt/Pd based nanocatalysts can be regulated by structural design,lattice expansion and disordered arrangement of atoms,improving the poisoning,deterioration and deactivation during the catalytic process of small molecular fuel,and significantly boost the catalytic activity,anti-poisoning ability and long-term catalytic stability of the catalyst.It provides a novel modification strategy and experimental reference for the design and development of high-efficiency DLFCs electrocatalysts.