First Principles Calculations on Site-Dependent Dissolution Potentials of Supported and Unsupported Pt Particles

Site-dependent redox potentials of the Pt dissolution reaction, Pt -> Pt2+(aq) + 2e(-), from Pt particles with and without carbon supports were calculated by a first principles method. The calculation result showed a clear site-dependence in which the redox potentials for the Pt atoms at edges are lower than those for Pt atoms at flat surfaces. This site-dependence is roughly correlated with the d-band center of the dissolving Pt atom, and Pt atoms with higher d-band centers dissolve more easily to the solution. The effects of perfect and defected graphenes on the redox potential are less than 0.1 V. For the platinum atom attaching to the carbons, a slightly negative effect (lowering the redox potential) is obtained, because the bond strength between Pt particles and carbons is enhanced by the defect creation alter the dissolution reaction.