(581a) PEFC Electrode Layer Development Via Complementary in Situ Diagnostics and Ex Situ Characterization (invited)

Authors: 
Neyerlin, K. C., National Renewable Energy Laboratory
Ink formulation and electrode design optimization is often an iterative process, in which conclusions from in situ performance/ diagnostics as well as ex situ characterization (e.g. microscopy and tomography) are relayed to a model. The model then identifies fundamental limiting phenomena which are to be improved in the next iterative cycle. This process often takes several iterations to ensure an optimal combination of ionic and gas phase accessibility to the active site.

The proper integration of materials to enable high performing low temperature fuel cell operation has never been more crucial to realizing the isolated (e.g. half-cell or ex-situ) improvements of advanced electrocatalysts, supports and ionomers. Variables such as ink formulation (i.e. solvents and solvent ratios), processing method, ionomer chemistry, carbon morphology/porosity and even the presence or absence of Pt, can impact the ink level interactions of the materials set and subsequently alter the final electrode morphology. The resulting electrode structure can in turn influence active site accessibility and ORR activity as well as oxygen transport resistance and electrode proton conductivity.1–5

Here, the development and utilization of in situ diagnostics designed to probe specific phenomena (e.g. catalyst/ionomer interactions, molecular and Knudsen diffusion, electrochemical active site accessibility and catalyst layer proton resistance) will be utilized to contrast the ink, processing and fabrication methods necessary to achieve high performance PGM (e.g. Pt/C and Pt alloy/C) and PGM-free (e.g. FeNx/C) electrocatalysts based electrodes.

References

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  2. S. Khandavalli et al., ACS Appl. Mater. Interfaces, 10, 43610–43622 (2018).
  3. D. Myers, https://www.hydrogen.energy.gov/pdfs/review15/fc106_myers_2015_o.pdf.
  4. F. Xu et al., Langmuir, 26, 19199–19208 (2010).
  5. D. A. Cullen et al., J. Electrochem. Soc., 161, F1111–F1117 (2014).