DFT calculations on electro-oxidations and dissolutions of Pt and Pt–Au nanoparticles

• Published in: Catalysis today Vol. 262; pp. 100 - 109
• Main Authors: Jinnouchi, Ryosuke, Suzuki, Kensaku Kodama Takahisa, Morimoto, Yu
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.03.2016
• Subjects: DFT; Dissolution; Oxidation; Oxygen reduction reaction; Pt nanoparticle; Oxidation; Pt nanoparticle; DFT; Dissolution; Oxygen reduction reaction
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/j.cattod.2015.08.020

•We examine DFT calculations on Pt and Pt–Au nanoparticles with a diameter of 2nm.•Thermodynamically stable oxide structures are clarified.•Edges and corners of the Pt nanoparticle are shown to be inactive and easily dissolving sites.•A substitutional introduction of Au atoms to Pt nano-particles is promising for suppressing Pt dissolutions without decreasing the number of active sites for ORR. DFT calculations were carried out on electro-oxidations and dissolutions of pure Pt and Pt–Au nanoparticles. Calculations indicated that electro-oxidations are initiated by OH adsorbate formations at (100)-edges of the pure Pt nanoparticle of 260 atoms at 0.5V (RHE). The formed OH adsorbates are replaced by O adsorbates at 0.75V, and the formed O adsorbates aggregate at (110)-edges of the nanoparticle to form 1-dimensional PtO2 chains. Further increase in the electrode potential causes gradual increases in O adsorbates at the facets of the nanoparticle, and the formed O atoms start sinking into the subsurfaces to form α-PtO2 monolayers at 1.18V. Calculations indicated that the edges of the pure Pt nanoparticle were covered too strongly with the O adsorbates at 0.9V to allow for adsorptions of oxygen molecules at those surface sites. Pt atoms located at the edges were, therefore, judged to be inactive for oxygen reduction reaction (ORR). The Pt atoms located at the edges were also shown to be easily dissolved into the solutions because they do not have strong binding energies with the particle. Further calculations on the Pt–Au nanoparticle indicated that the corrosive Pt dissolutions can be suppressed by subtitutional introductions of Au atoms at the edges of the nanoparticle without lowering ORR activity.