Title: Toward Optimizing Electrospun Nanofiber Fuel Cell Catalyst Layers: Microstructure and Pt Accessibility

Abstract

This work investigates how local ionomer/platinum (Pt) interactions and ionomer distribution in electrospun Pt/Vulcan nanofiber electrodes impact ionomer coverage, proton accessibility, and oxygen reduction reaction (ORR) performance in proton-exchange membrane fuel cells. Insights from various in situ electrochemical diagnostics were utilized in conjunction with ex situ microscopic characterization to understand how the electrode microstructure—both at the aggregate level and near the ionomer/platinum interface—is affected by electrospinning in comparison to ultrasonic spraying. The effect of the carrier polymer poly(acrylic acid) (PAA) concentration from 5–20 wt % (with respect to total ink solids) on the resulting nanofiber morphology is discussed. Electron microscopy observations and CO displacement measurements indicated that Pt/Vulcan nanofibers prepared with a higher PAA concentration (15 wt %) were conformally coated with a film of ionomer on the exterior of the fiber, which resulted in an overall lower ionomer coverage on both Pt and carbon throughout the fiber diameter. In contrast, 10 wt % PAA leads to a uniform intrafiber distribution of the ionomer within the fibers, increasing the overall ionomer coverage and proton accessibility under both wet and dry conditions. These differences in the local ionomer coverage on Pt between 10 and 15 wt % PAA were also attributedmore » to differences in the adsorption/interaction affinities between PAA and the ionomer onto the catalyst surface in the ink using zeta potential measurements. Additional fuel cell electrochemical tests on the electrospun electrodes show improvements in ORR kinetics and high-current-density H₂/air performance compared to the ultrasonically sprayed electrodes.« less

Authors:

Kabir, Sadia  ^[1];

• Search DOE PAGES for author "Kabir, Sadia"
• Search DOE PAGES for ORCID "0000-0002-5064-7916"

Van Cleve, Tim  ^[1];

• Search DOE PAGES for author "Van Cleve, Tim"
• Search DOE PAGES for ORCID "0000-0001-7233-5844"

Khandavalli, Sunilkumar  ^[1];

• Search DOE PAGES for author "Khandavalli, Sunilkumar"
• Search DOE PAGES for ORCID "0000-0003-3179-5718"

Medina, Samantha ^[2]; Pylypenko, Svitlana  ^[2];

• Search DOE PAGES for author "Pylypenko, Svitlana"
• Search DOE PAGES for ORCID "0000-0001-7982-734X"

Mauger, Scott  ^[1];

• Search DOE PAGES for author "Mauger, Scott"
• Search DOE PAGES for ORCID "0000-0003-2787-5029"

Ulsh, Michael  ^[1];

• Search DOE PAGES for author "Ulsh, Michael"
• Search DOE PAGES for ORCID "0000-0003-3725-8032"

Neyerlin, Kenneth C.  ^[1]

• Search DOE PAGES for author "Neyerlin, Kenneth C."
• Search DOE PAGES for ORCID "0000-0002-6753-9698"

---

+ Show Author Affiliations

1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
2. Colorado School of Mines, Golden, CO (United States)

Publication Date:

Mon Mar 22 00:00:00 EDT 2021

Research Org.:

National Renewable Energy Lab. (NREL), Golden, CO (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE), Hydrogen and Fuel Cell Technologies Office (EE-3F); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Energy Efficiency Office. Advanced Manufacturing Office

OSTI Identifier:

1774883

Report Number(s):

NREL/JA-5900-79533
Journal ID: ISSN 2574-0962; MainId:33759;UUID:c9889ad8-e471-46d4-ab1b-2b4da3e645e4;MainAdminID:21202

Grant/Contract Number:  

AC36-08GO28308

Resource Type:

Accepted Manuscript

Journal Name:

ACS Applied Energy Materials

Additional Journal Information:

Journal Volume: 4; Journal Issue: 4; Journal ID: ISSN 2574-0962

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

25 ENERGY STORAGE; PGM-free catalyst; oxygen reduction; fuel cell; electrospinning; electrochemical diagnostics