CO Tolerance of PEMFC Anodes: Mechanisms and Electrode Designs

Abstract

This work presents a review of the current literature regarding the CO tolerance on PEM fuel cells feed with H2 containing CO. From bulk metal alloys to nanoparticles, we summarize the present understanding of what is necessary to achieve the CO tolerance. A discussion is given on the tolerance mechanisms for binary Pt-alloys, emphasizing the achievements gained by using coupled techniques such as X-ray absorption spectroscopy and mass spectrometry. Together with the commonly accepted CO tolerance mechanisms, the so-called bifunctional and electronic mechanisms, alternative chemical pathways are presented as reactions that consume gas-phase CO and the role of such tolerance methods is assessed on the overall cell performance. A brief discussion on the perspective electrocatalysts and improved CO tolerance methods is given to account for the CO tolerance at higher CO contents in the H2 stream, emphasizing the various ways to increase tolerance, whether by oxidation, reduction, or by changes in the CO adsorption/desorption properties.