--- res: bibo_abstract: - An experimental technique for measuring the current density distribution with a resolution smaller than the channel/rib scale of the flow field in polymer electrolyte fuel cells (PEFCs) is presented. The electron conductors in a plane perpendicular to the channel direction are considered as two-dimensional resistors. Hence, the current density is obtained from the solution of Laplace's equation with the potentials at current collector and reaction layer as boundary conditions. Using ohmic drop for calculating the local current, detailed knowledge of all resistances involved is of prime importance. In particular, the contact resistance between the gas diffusion layer (GDL) and flow field rib, as well as GDL bulk conductivity, are strongly dependent on clamping pressure. They represent a substantial amount of the total ohmic drop and therefore require careful consideration. The detailed experimental setup as well as the concise procedure for quantitative data evaluation is described. Finally, the method is applied successfully to a cell operated on pure oxygen and air up to high current densities. The results show that electrical and ionic resistances seem to govern the current distribution at low current regimes, whereas mass transport limitations locally hamper the current production at high loads.@eng bibo_authorlist: - foaf_Person: foaf_givenName: Stefan Alexander foaf_name: Freunberger, Stefan Alexander foaf_surname: Freunberger foaf_workInfoHomepage: http://www.librecat.org/personId=A8CA28E6-CE23-11E9-AD2D-EC27E6697425 orcid: 0000-0003-2902-5319 - foaf_Person: foaf_givenName: Mathias foaf_name: Reum, Mathias foaf_surname: Reum - foaf_Person: foaf_givenName: Jörg foaf_name: Evertz, Jörg foaf_surname: Evertz - foaf_Person: foaf_givenName: Alexander foaf_name: Wokaun, Alexander foaf_surname: Wokaun - foaf_Person: foaf_givenName: Felix N. foaf_name: Büchi, Felix N. foaf_surname: Büchi bibo_doi: 10.1149/1.2345591 bibo_issue: '11' bibo_volume: 153 dct_date: 2006^xs_gYear dct_isPartOf: - http://id.crossref.org/issn/0013-4651 dct_language: eng dct_publisher: The Electrochemical Society@ dct_title: Measuring the current distribution in PEFCs with sub-millimeter resolution@ ...