| AVS 65th International Symposium & Exhibition | |
| Applied Surface Science Division | Thursday Sessions |
| Session AS-ThP |
| Session: | Applied Surface Science Division Poster Session |
| Presenter: | Sarah Zaccarine, Colorado School of Mines |
| Authors: | S.F. Zaccarine, Colorado School of Mines C. Ngo, Colorado School of Mines S. Shulda, National Renewable Energy Laboratory S. Mauger, National Renewable Energy Laboratory S.M. Alia, National Renewable Energy Laboratory K.C. Neyerlin, National Renewable Energy Laboratory B.S. Pivovar, National Renewable Energy Laboratory S. Pylypenko, Colorado School of Mines |
| Correspondent: | Click to Email |
In response to the increasing anthropogenic impact on the environment, it is vital to implement sustainable solutions to meet global energy demands. Polymer electrolyte membrane fuel cells (PEMFCs) are a promising option but the sluggish oxygen reduction reaction at the cathode leads to issues with cost and efficiency. Pt nanoparticles supported on high surface area carbon (Pt/HSC) are commonly used but suffer performance losses and do not meet Department of Energy targets for durability or cost. Extended surface nanostructures are a promising alternative as they show improved specific activity and durability. We have developed extended surface nanowire-based platinum nickel catalysts with durability, mass activity, and specific activity superior to Pt/HSC. Since the catalyst functions differently under altered conditions, it is crucial to study the catalyst at all stages as it transitions from a powder to a membrane electrode assembly (MEA), which requires a multi-technique approach.
The catalyst was studied as a powder, ink, fresh MEA, and tested MEA to determine the changes that occur as the catalyst is integrated into a full MEA. Several spectroscopy and microscopy techniques were utilized to address all relevant length scales (from atomic to micrometers). First, the catalyst was investigated using a combination of extended x-ray absorption fine structure (EXAFS) spectroscopy, x-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM) with energy dispersive x-ray spectroscopy (EDS) hypermapping, and atom probe tomography (APT) to obtain detailed information about distribution of platinum and nickel, discerning differences between surface and bulk speciation at nanometer and sub-nanometer scale. This detailed information about surface speciation was then used to better understand oxygen adsorption behavior of these catalysts, investigated using near-ambient pressure XPS (nAP-XPS). Second, evolution of the catalyst and catalyst-ionomer interface when incorporated in an electrode were examined with STEM/EDS and x-ray tomography. These studies offer invaluable insight into structure-performance relationships of the nanowire-based catalysts and development of efficient electrodes.