Catalyst Layer Degradation, Diagnosis and Failure Mitigation

Catalyst Layer Degradation, Diagnosis and Failure Mitigation 

The functions of porous electrodes in fuel cells are 1) to provide a surface site for gas ionization or de-ionization reactions, 2) to provide a pathway for gases and ions to reach the catalyst surface, 3) to conduct water away from the interface once these are formed, and 4) to allow current flow. A membrane electrode assembly (MEA) forms the core of a fuel cell and the key electrochemical reactions take place in the MEA. MEA performance is severely affected by electrode composition, structure, and geometry, and especially by cathode structure and composition, due to poor oxygen reduction kinetics and transport liniitations of the reactants in the cathode catalyst layer. 

Catalytic layers in the anode and cathode are also critical components in a PEMFC. Platinum (Pt) or a Pt-Ru alloy supported by nano-carbon particles is often used as the catalyst in the anode [1-6]. Favorable electronic properties have been suggested by density-functional theory studies, which have shown fliat flie CO adsorption energy is the lowest on the Pt monolayer located above Ru compared with the adsorption energies on pure Pt, pure Ru, and a Pt-Ru mixed surface layer over Pt [7, 8], The bifunctional mechanism [4] suggests that Ru provides an active surface for oxidative removal of adsorbed CO at the neighboring Pt sites. Thus, a 

Pt-Ru alloy catalyst wifli high CO tolerance is used in the anode, especially when a reformate H2-rieh gas (in which CO content is high) is used for fuel. 

2 Diagnosis of Catalyst Layer Degradation Fuel Cell Failure Analysis 

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