Study On The Regulation Of Electrode Phase And Surface Structure Of Pt - Cu Alloy Nanometer Catalyst And Its Electrochemical Performance

As the most promising efficient and cleanest energy in 21st century, Fuel cells have been acknowledged due to their advantages, such as high energy conversion efficiency, slight pollution, low noise and quick-startup, etc. Platinum (Pt) is used as catalysts anode and cathode for Proton exchange membrane fuel cell (PEMFC) commonly. Compared to the hydrogen oxidation reaction (HOR) rate of the anode, the cathodic oxygen reduction reaction (ORR) is much slower. So, in order to promote the cathodic reaction, much more noble metal platinum (Pt) is needed. Because of the expensive and scarce resources, the Pt catalysts become high cost and restrict the commercial application of fuel cell. In order to reduce the dosage of Pt, people mainly reduce the cost through preparing Pt-M alloy catalyst with some 3d transition metal (such as:M=Fe, Co, Cu and Ni), and improving the ORR activity and stability of the catalyst through the regulation of Pt alloy nanoparticles size, morphology and phase structure.For the paper, the Pt/C powder was putted into a certain concentration of nitric acid copper (Cu(NO3)2), the solution is ultrasonic mixed, and the Pt and Cu molar ratio is controlled of 3:1, 1:1 and 1:3.Then the mixed solution is freezed drying. Lastly, the precursor powder is heated to 800℃ quickly under N2 and N2+H2 for 30,60 and 90 min respectively, and rapidly cooling to room temperature and then the Pt-Cu alloy nanoparticles catalysts was got. And the electrochemical dealloy is used to regulate the nanoparticles surface structure of Pt-Cu alloy. XRD, TEM, HR-TEM and XPS are used to study Pt-Cu nanoparticle size, morphology and phase structure, Chemical composition and chemical valence state, then electrochemical method to test the performance of catalyst Pt-Cu alloy.(1) Regulatting the surface structure and crystal phase structure of Pt-Cu alloy through different treatment atmosphere, the Pt-Cu alloy nanoparticles evenly dispersed on the surface of the carbon carrier which forming under N2+H2 and N2. The average particle size of the alloy nanoparticles under N2 should be bigger than the size alloy nanoparticlesunder N2+H2; the forming of Pt-Cu alloy nanoparticles under the N2 and N2+H2 with different mole ratio has obviously discrepant phase structure. Especially, with the condition of 800℃ thermal 60 min under N2 can form ordered PtCu3, and Pt-Cu alloy appears surface segregation phenomenon under N2+H2;(2) Pt-Cu alloy phase structure and surface structure has serious impact on its catalytic performance. Pt and Cu with the molar ratio of 1:3 possesses the best electric catalytic performance with the condition of 800℃ thermal 90 min under N2; under N2+H2, Pt and Cu with the mole ratio of 1:1,800℃ thermal 90 min has the best electric catalytic performance;(3) by using cyclic voltammetry dissolve Cu atoms which on the Pt-Cu alloy nanoparticles surface can form core-shell structure that the surface is Pt rich, and their catalytic properties indexes of initial reduction potential, half wave potential and the limiting current density all increasing with varying degrees. Pt and Cu with the molar ratio of 3:1 possesses the highest half wave potential with the condition of 800℃ thermal 60 min under N2; under N2+H2, Pt and Cu with the mole ratio of 1:1,800℃ thermal 30 min has the highest half wave potential.