First-principles Calculations of Metal Dissolution on Pt/Ni(111) and Pt(111) surfaces at Applied Bias Potential

1.Abstract

The reliability and durability of Proton exchange membrane fuel cells (PEMFC) have been recognized as a major research interest. Among the performance-reduction factors of PEMFC in long-term operation is the dissolution of platinum (Pt) catalysts. In addition, recent experimental findings have demonstrated that Pt dissolution under potential cycling was significantly enhanced by the presence of chloride at high potentials. Several studies have also indicated that bare Pt surface is prone to anodic Pt dissolution because of low oxygen coverage on Pt surface at steep high potentials. However, majority of past experimental studies have not elaborated Pt dissolution process on alloyed PtNi nanocatalysts which have been proven experimentally to have superior catalytic activity as compared to those Pt catalysts.
The proposed research program here is meant to investigate the mechanism of metal dissolution on bimetallic PtNi(111) and Pt(111) surfaces with and without the presence of chloride by implementing effective screening medium (ESM) method in density functional theory (DFT) calculations. Thus, by incorporating ESM method, charged NiPt and Pt(111) surfaces could be introduced and Pt dissolution mechanism at those charged surfaces could be studied thoroughly at atomistic level.

2.Keywords
PEMFC, Pt, PtNi, dissolution, DFT
3.Objective

investigate metal dissolution mechanisms on Pt and PtNi nanocatalysts.

4.Methodology

We use the density functional theory (DFT) in order to study Pt and PtNi nanocatalysts dissolution. The simulated PtNi(111) and Pt(111) surfaces should be charged by adding or reducing the total charge of the system. This work can be done by implementing ESM to generate charged surfaces that approximately resemble the environmental conditions of Pt nanocatalysts during potential cycling.
The preliminary study on Pt(111) surface will be performed to serve as reference and also benchmark for PtNi(111) surface. To construct clean Pt(111) surface, a periodic supercell of size 15.71 � x 15.71 � x 45.45 � consisting 45 Pt atoms (5 layers) would be employed where each layer comprises of 9 Pt atoms. All calculations are performed using Quantum Espresso program by implementing the generalized gradient approximation (GGA) with Perdew-Burke-Ernzerhof (PBE) for the exchange correlation functional and the projector-augmented-wave (PAW) method by using a plane-wave cutoff energy of 47 Ry. The Brillouin zone integration was performed using a grid of 5 � 5 � 1 Monkhorst-Pack mesh. These values of cutoff energy and k-points were chosen based on convergence tests using a system of single oxygen atom adsorbed on 5-layer Pt(111) surface.

5.Team

Wahyu Tri Cahyanto
Department of Physics, Universitas Jenderal Soedirman, Purwokerto

Ferensa Oemry
Research Center for Physics - LIPI

6.Computation plan (required processor core hours, data storage, software, etc)

48 proc, 30 GB data storage, software quantum espresso

7.Source of funding
none
8.Target/outputs
1 international publication per year
9.Date of usage
02/03/2017 - 30/11/2019
10.Gpu usage
-
11.Supporting files
prop_1488358174.pdf
12.Created at
01/03/2017
13.Approval status
approved