Cyclic Voltammetry Study of Ice Formation in the PEFC Catalyst Layer during Cold Start

A cyclic voltammetry technique has been developed to investigate the effect of ice formation in the cathode catalyst layer CL on electrochemically active Pt area during and post-subzero startup of a polymer electrolyte fuel cell PEFC. It was found that the Pt area decreases after each cold start and the Pt area loss increases with the product water generated during cold start. We hypothesize that the Pt area loss is caused by ice precipitated between Pt particles and ionomers during cold start. After startup from a subzero temperature and warmup to 25°C with all ice in the CL melted, the cell remains subject to Pt area loss, but this loss at 25°C is substantially reduced. We also find that subsequent cell operation at 70°C and 1 A/cm 2 for 2 h is very effective for recovering the active Pt area and cell performance. Both permanent loss in the active Pt area and cell performance degradation due to structural alteration of the cathode CL by the presence of ice increase gradually with the cold-start cycle number and become more severe for cold start from �30°C than from �10 and �20°C. In addition, startup from a subzero temperature appears to have no influence on the electrochemically active Pt area of the anode CL. It is suggested that the ice amount present in the CL holds a key to determine the temporary Pt area loss due to ice formation as well as permanent performance degradation resulting from cold-start cycling.

[1]  Dirk Riemann,et al.  Low temperature operation and influence parameters on the cold start ability of portable PEMFCs , 2006 .

[2]  J. Jorné,et al.  Investigation of Low-Temperature Proton Transport in Nafion Using Direct Current Conductivity and Differential Scanning Calorimetry , 2006 .

[3]  Qunhui Guo,et al.  Effect of freeze-thaw cycles on the properties and performance of membrane-electrode assemblies , 2006 .

[4]  U. Stimming,et al.  Conductance of Nafion 117 membranes as a function of temperature and water content , 1995 .

[5]  Shanhai Ge,et al.  Characteristics of subzero startup and water/ice formation on the catalyst layer in a polymer electrolyte fuel cell , 2007 .

[6]  In-Hwan Oh,et al.  Effects of Water Removal on the Performance Degradation of PEMFCs Repetitively Brought to < 0 ° C , 2004 .

[7]  Ulrich Stimming,et al.  Proton conduction of Nafion® 117 membrane between 140 K and room temperature , 1994 .

[8]  In-Hwan Oh,et al.  Characteristics of the PEMFC Repetitively Brought to Temperatures below 0°C , 2003 .

[9]  Mario Zedda,et al.  Statistic analysis of operational influences on the cold start behaviour of PEM fuel cells , 2005 .

[10]  Supramaniam Srinivasan,et al.  Analysis of proton exchange membrane fuel cell performance with alternate membranes , 1995 .

[11]  Shanhai Ge,et al.  In Situ Imaging of Liquid Water and Ice Formation in an Operating PEFC during Cold Start , 2006 .

[12]  Kikuko Hayamizu,et al.  Temperature dependence of ion and water transport in perfluorinated ionomer membranes for fuel cells. , 2005, The journal of physical chemistry. B.

[13]  Tomohiro Ogawa,et al.  The Design and Performance of a PEFC at a Temperature Below Freezing , 2004 .

[14]  Chao-Yang Wang,et al.  A Multiphase Model for Cold Start of Polymer Electrolyte Fuel Cells , 2007 .

[15]  Chao-Yang Wang,et al.  Effects of operating and design parameters on PEFC cold start , 2007 .

[16]  R. Mcdonald,et al.  Effects of Deep Temperature Cycling on Nafion® 112 Membranes and Membrane Electrode Assemblies , 2004 .

[17]  Chao-Yang Wang,et al.  Isothermal Cold Start of Polymer Electrolyte Fuel Cells , 2007 .

[18]  Chao-Yang Wang,et al.  Analysis of Cold Start in Polymer Electrolyte Fuel Cells , 2007 .