First Principle Theoretical Study Of Oxygen Reduction Reaction On Pt Pt-Based Alloys

To enhance the oxygen reduction reaction (ORR) rate of cathode of proton exchange membrane fuel cell, Pt-based bimetallic nanoparticles as potential cathode materials have been widely studied. Up to now, numerous Pt-based bimetallic nanoparticles have been fabricated, in which it is essential that ensuring the Pt surface as the reactive surface while alloying metals in subsurfaces to reduce costs. In this thesis, for the existing problems associated with the ORR activity of Pt-Ni alloys, we perform theoretical studies using first-principles calculations based on density functional theory.The first part is focused on the formation and the property of Pt-skin of PtNi3 nanoparticles during electrochemical corrosion. A series of layer-dependent Pt-skin models are proposed and investigated. It is found that the electrochemical corrosion makes the surface Ni atoms be removed, leaving the Pt atoms to form the Pt-rich layers. The calculated oxygen binding energy shows that the layer-dependent Pt-rich surface would have better ORR activitv than PtNi3.In the second part, we propose an adsorption/contact modification strategy totailor the surface property of Pt catalystsfrom the exterior. The stability of boron (B) species on the Pt (111) surface, and the oxidation of Boron discussed.Similarly, the casesand effects of B-Ni dimerson the Pt(111)surface are studied. The surface B is oxidized to finally form BO2 or BNiO2 clusters on the Pt(111) surface, making the oxygen binding energy approximateto the optimal value, thus improving oxygen hydrogenation kinetics in the ORR process. Especially, the modulation mechanism from practical metal borides membrane of the ORR activity of Pt is explored.In the third part, we study the solvation effects on the ORR process of boride-covered Pt catalysts using the free energy as the criterion at the operating voltage of 0.9V. Results again confirm that the presences of BO2 or BNiO2 clusters on the Pt(111) surface would be beneficial to the enhancement of the ORR performance.The underlying mechanism is also exploredvia the formation of the hydrogen bond network.