Effect of Surface Ni on Oxygen Reduction Reaction in Dealloyed Nanoporous Pt−Ni
Venkataramana Imandi* and Abhijit Chatterjee*
*Indian Institute of Technology Bombay
*E-mail: abhijit[at]chem.iitb.ac.in
High specific surface area nanoporous Pt−Ni synthesized via selective dissolution of Ni exhibits a high catalytic activity toward the oxygen reduction reaction (ORR). Using kinetic Monte Carlo simulations, we show that the elemental distribution in nanoporous Pt−Ni is different from the well-understood Pt-skin Pt−Ni catalyst. In nanoporous Pt−Ni, both the surface and subsurface layer are rich in Pt. Crucially, a small amount of Ni is present in the surface layer. Using density functional theory, we show that the presence of Ni in the surface layer in nanoporous Pt−Ni can speed up the ORR by orders of magnitude. Different Pt−Ni atom arrangements in the surface layer are considered. Our simulations show that the OH formation step that is the rate-limiting step for the ORR is the same for the Pt−Ni(111) surface. The low concentration of surface Ni explains why nanoporous Pt−Ni provides only 10 times improvement in ORR rates over the pure Pt catalyst1.
References:
(1) Venkataramana Imandi and Abhijit Chatterjee, Effect of surface Ni on oxygen reduction reaction in dealloyed nanoporous Pt-Ni, Ind. Eng. Chem. Res., 2018, DOI: 10.1021/acs.iecr.8b05204.