Microstructural Modulation And Bifunctional Application Of PtNi Nanocatalyst

Proton exchange membrane fuel cell（PEMFC）,as an energy conversion equipment,can alleviate energy shortage and environmental pollution,and can convert chemical energy into electric energy.In addition to many advantages,such as less pollution to the environment,stable performance,long service life,high energy conversion efficiency from chemical energy to electrical energy,and quick start-up at room temperature,the development of PEMFC still faces the technical challenge of further improving the efficiency of electrocatalysts.Although Pt-based catalyst is the most commonly used and most efficient electrocatalyst at present,its wide application is restricted by the limited reserves and high price of precious metal Pt.Therefore,this problem can be alleviated by optimizing the design of Pt-based nanocatalyst.In this paper,the bifunctional PtNi nanostructured electrocatalysts were designed and synthesized based on"component control strategy"and"morphology control strategy",and their electrocatalytic performance,such as catalytic oxygen reduction reaction（ORR）and catalytic methanol oxidation reaction（MOR）performance,were studied.The specific research contents are as follows:（1）PtNi multi-branched nanostructures（PtNi MBNs）were synthesized by a simple one-step solvothermal method by adjusting the dosage of precursor Pt and Ni and the reaction temperature.It has a unique multi-branched structure that can provide more active sites and a Pt-rich surface,which is conducive to the improvement of catalytic performance.The performance of the catalyst was tested in acidic environment,and it was found that the multi-branch structure can catalyze cathode ORR and anode MOR at the same time,and it has excellent bifunctional electrocatalytic performance.The test results show that the half-wave potential of catalytic ORR is 0.966 V,which is much higher than that of commercial Pt/C（0.931V）,and it only drops by 14 m V after 8,000 cycles.For MOR,the specific activity（SA）of PtNi MBNs is 18.1 A m_Pt^-2,which is 2.3 times that of commercial Pt/C(7.8 A m_Pt^-2).The CO stripping experiment simulated the external environment filled with CO,which verified the excellent anti-poisoning ability of the sample,and further confirmed its excellent catalytic activity and stability.The remarkable bifunctionality of PtNi MBNs is attributed to the high electrochemical surface area,abundant atomic steps and Pt-rich surface provided by unique multi-branched nanostructures.（2）The PtNi polyhedral nanochain structure（PtNi PNCs）was designed.The ordered PtNi polyhedral nanochain with rich（111）faces are self-assembled from polyhedral particles and nanorods,and rich atomic steps provide a large number of active sites,which is conducive to the rapid charge transfer.Nanopolyhedron is one of the components of PtNi PNCs,with an average size of about 6 nm,and the diameter of the main nanowire is only 2 nm.And maintains high catalytic activity of ORR and MOR in long-term rigorous stability tests.Compared with commercial Pt/C,the mass activity（MA）of PtNi PNCs for catalytic ORR is 3.34 times and SA is 3.79 times.After10,000 cycles,the half-wave potential only shifts by 17 m V,and the stability is much better than that of commercial Pt/C（55 m V）.At the same time,the catalytic activity of MOR is also significantly better than that of commercial Pt/C,and MA and SA are 7.23and 6.55 times of commercial Pt/C,respectively.This strategy may provide an ideal method for catalyst preparation to balance the contradiction between catalytic activity and catalytic stability.