Proton exchange membrane fuel cells platinum-free oxygen reduction and performance degradation by start-up/shut-down events

Two major hindrances prevent proton exchange membrane fuel cells (PEMFCs) from being of widespread commercial success: high costs and limited durability. One of the main cost contributors is platinum which is currently used in the catalyst layers, mainly for the oxygen reduction reaction. This work aims for a comprehensive understanding of the oxygen reduction electrocatalysis associated with two specific platinum-free materials, palladium and completely noble-metal-free transition metal oxides. Among other lifetime limiting factors, the transient operation state of start-up and/or shut-down of PEMFCs has proven to be extremely invasive for the cathode electrode integrity. In this respect, we strive to provide an extensive understanding of the main parameters influencing degradation during repeated start-up/shut-down of PEMFCs. In this Ph. D. thesis, I cumulatively integrate two scientific publications and two additional sections with manuscripts submitted/prepared for publication that emerged from my work at the Chair of Technical Electrochemistry (TEC), Technical University of Munich. An introduction will be followed by a brief over-view and description of the main experimental methods applied. Results of the conducted studies are presented in accordance to the before mentioned topical PEMFC issues. The thesis concludes with a review of the presented findings in the context of PEMFC cost and durability.