Transient Multi-Scale Modeling of PtxCoy Catalysts Degradation in PEFC Environments

Abstract

In this paper we focus on the understanding of the PtxCoy catalysts degradation in PEFC environments. A multiscale atomistic/kinetic model is derived providing new mechanistic insights on the impact of clusters nanostructure and operating conditions on PtxCoy materials durability. On the basis of ab initio (AI) data, we identify favorable pathways of the ORR on PtxCoy clusters and of the competitive Pt-Co dissolution in acidic media. The derived AI-kinetics is coupled to a description of the atomic reorganisation at the cluster level as function of the cumulated Pt and Co mass losses. This interfacial model is coupled with a transport microscale model of charges and O2 through the PEFC cathode, and simulation sensitivity studies to operating conditions and initial compositions/morphologies are performed. Experiments on DLIMOCVD-elaborated model electrodes are carried out by using RDE and half-cells: degradation structural changes are characterized by using TEM, XRD and XPS complementing the modeling studies.

Carbon Catalyst-Support Corrosion in Polymer Electrolyte Fuel Cells: Mechanistic Insights

“…Furthermore, we are now actively working on the extension of our approach for describing the coupling between the bi-metallic electro-catalysts degradation and the ORR taking place on. For example, we have recently proposed a new dynamic mechanistic description of the ORR on ageing Pt x Co y electro-catalytic aggregates in a PEFC cathode environment (41): the impact of the catalyst nature on the carbon corrosion will be studied. Coupling of this model with carbon corrosion model will be envisaged to try to try to correlate with Ball et al experiments (8).…”

“…Our multi-scale mechanistic model of the PEFC MEA electro-catalysis is designed to match atomistic and macroscopic theories, and can be fully parametrized by using ab initio calculated and surface science data (41). The model discussed here describes the MEA transient behaviour, on the basis of auto-consistent physical-based mechanistic descriptions of th polymer electrolyte membrane (PEM) and catalytic layers.…”

Microstructure-Based Modeling of Aging Mechanisms in Catalyst Layers of Polymer Electrolyte Fuel Cells

“…Ab-initio data are used to determine the more favorable pathways of the HOR/ORR and essential steps of the carbon corrosion reaction, as well as the associated energetic properties (transition-state activation barriers). The methodological details are given elsewhere. − , …”

“…The model is built on the basis of the irreversible thermodynamics theory and particularly adapted for the description of nonequilibrium physicochemical systems. It has been successfully applied to address the feedback between materials degradation processes (e.g., Pt and Pt–M oxidation, dissolution and ripening, PEM degradation), their impact on performance decay, and the local operating conditions at the cell level. ,,,− Regarding the CB degradation, an agglomerate-fractal-like model was employed to represent the CCL microstructure. In this model, the structural properties such as porosity, electronic conductivity, and electrode thickness before and after corrosion process were fitted to experimental data. , The corrosion process is described by an elementary kinetics approach.…”

Multiscale modelling and numerical simulation of rechargeable lithium ion batteries: concepts, methods and challenges

“…193 The idea behind is similar to the indirect multiparadigm model proposed by Franco et al coupling a MC-generated database with continuum multiscale simulations to describe the feedback between catalyst Pt x Co y nanoparticles dissolution and PEMFC instantaneous performance. [194][195][196][197] Northrop et al goal is to calculate the passive layer formation from the SEI layer, and to be incorporated in the porous electrode model. Conversely, the porous electrode model aims to calculate the liquid-phase concentrations and the overpotential at all points and times so that the probability of each event can be calculated for use in the KMC simulations.…”