Rapid activation of a full-length proton exchange membrane fuel cell stack with a novel intermittent oxygen starvation method

Activation/conditioning/break-in is a critical step for newly manufactured proton exchange membrane fuel cell (PEMFC) stacks to meet the factory standard. A new in situ activation approach, intermittent oxygen starvation (IOS), is introduced for the first time by combining load cycling activation (LCA) with hydrogen pumping mechanism. IOS occurs during drawing current from a stack while discontinuously decrease the stoichiometry of the cathode oxygen to an extremely low level (<1). The effect of IOS is tested with 3-cell short stacks and compared with LCA. Experimental results exhibit that IOS shows much faster activation speed than LCA, and only 35 min is necessary for IOS versus 105 min for LCA. Furthermore a full-length stack, which has 370 cells, is activated with IOS. After activation the average cell voltage reaches 0.667 V at 1200 mA cm−2, equivalent to the rated stack power of 101.1 kW. Meanwhile hydrogen consumption decreases from 124,000 NLPM (LCA) to 74,000 NLPM (IOS). Postmortem examination of atomic force microscopy (AFM) reveals that more exposure of the cathode Pt/C particles to the surface of catalyst surface and their uniform dispersion within ionomers after IOS activation is helpful for the quickly shaping of catalyst-ionomer-reactant three phase region (TPR).