TY  - JOUR
AU  - Ramaker, D. E.
AU  - Korovina, A.
AU  - Croze, V.
AU  - Melke, J.
AU  - Roth, C.
TI  - Following ORR intermediates adsorbed on a Pt cathode catalyst during break-in of a PEM fuel cell by in operando X-ray absorption spectroscopy
JO  - Physical chemistry, chemical physics
VL  - 16
IS  - 27
SN  - 1463-9084
CY  - Cambridge
PB  - RSC Publ.
M1  - PUBDB-2014-04280
SP  - 13645 - 13653
PY  - 2014
N1  - (c) the Owner Societies. Code P.
AB  - In operando X-ray absorption spectroscopy data using the Δμ X-ray Absorption Near Edge Spectroscopy (XANES) analysis procedure is used to follow the ORR intermediate adsorbate coverage on a working catalyst in a PEMFC during initial activation and break-in. The adsorbate coverage and log i (Tafel) curves reveal a strong correlation, i.e., an increase in adsorbate intermediate coverage poisons Pt sites thereby decreasing the current. A decrease in Pt–O bond strength commensurate with decrease in potential causes a sequence of different dominant adsorbate volcano curves to exist, namely first O, then OH, and then OOH exactly as predicted by the different ORR kinetics mechanisms. During break-in, the incipient O coverage coming from exposure to air during storage and MEA preparation is rather quickly removed, compared to the slower and more subtle nanoparticle morphological changes, such as the rounding of the Pt nanoparticle edges/corners and smoothing of the planar surfaces, driven by the nanoparticle's tendency to lower its surface energy. These morphological changes increase the Pt–Pt average coordination number, decrease the average Pt–O bond strength, and thereby decrease the coverage of ORR intermediates, allowing increase in the current.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000338116700012
C6  - pmid:24664398
DO  - DOI:10.1039/c4cp00192c
UR  - https://bib-pubdb1.desy.de/record/192751
ER  -