NEWS RELEAS

November 27th, 2023

Evaluation of correlation between catalyst surface hydrophilicity
and ionomer dispersion and durability in water-generating load
cycle tests on polymer electrolyte fuel cells:
Revealing that the control of functional groups through surface treatment of Pt/C
catalysts helps improve the ionomer dispersibility and durability

N.E. CHEMCAT CORPORATION (Headquarters: Minato-ku, Tokyo, Japan; President: Susumu Endo)announced results from an evaluation of correlation between the functional groups and hydrophilicity for afuel cell catalyst in a water-generating load cycle for polymer electrolyte fuel cells (PEFCs). The study
demonstrated that optimal ionomer (electrolyte polymer) dispersion and improved durability may beachieved through appropriate control of the catalyst surface condition, including surface treatment for
platinum carbon (Pt/C) catalyst to control functional groups. These results have been reported in anarticle in a journal of the American Chemical Society (ACS), ACS Applied Energy Materials, published on
November 27th and selected as a Supplementary Cover Art.
■ Key points of the announcement:
・ The study evaluated how the dispersion and durability of the ionomer might be influenced bychanges in the hydrophilicity of Pt/C catalyst as a result of its surface treatment that controls thefunctional groups on its surface
・ Compared to the excessively hydrophilic Pt/C catalyst, one with moderately decreased hydrophilic
properties demonstrated greater ionomer dispersibility and superior I-V performance
・ In durability tests under conditions where water was generated during power generation, whichwere similar to the actual operating environment of fuel cell vehicles (FCVs), the Pt/C catalyst withmoderately decreased hydrophilic properties was also associated with improved durability
compared to one with excessively hydrophilic properties
・ These results suggest that the control of catalyst surface condition may contribute to theoptimization of MEA structure and improvement in its durability
Fuel cells are clean power generation systems that generate electricity without emitting CO 2 and othergreenhouse gases, holding promise as a technology to help achieve carbon neutrality. Among them arePEFCs, which have found different applications such as fuel cell vehicles (FCVs), owing to their highpower generation efficiency. As countries seek to apply them to large-sized commercial vehicles, they are
calling for an improved performance and durability of membrane-electrode assemblies (MEAs), which area core component of fuel cells, to achieve higher output density and a final guaranteed distanceexceeding one million kilometers. In addition, we are seeing increasing demand for lower prices throughreduced use of precious metals such as platinum (Pt), with the U.S. Department of Energy (DOE) setting
a target to achieve fuel cell systems costs to $60/kW by 2040.
In this study, correlation between the functional groups and hydrophilicity of fuel cell catalyst constituting
the MEAs was tested.

1/4

NEWS RELEAS

The study first found that the hydrophilicity of catalyst was influenced primarily by the amounts offunctional groups and Pt oxide, rather than by Pt surface area. It further revealed that the amounts offunctional groups and Pt oxide on the Pt/C catalyst could be controlled using a proprietary surface
treatment method (Figure 1) to adjust the hydrophilic properties of the catalyst surface (Figure 2).

Figure 1. A schematic diagram of Pt/C catalysts withsurface treatment

Figure 2. Results of analysis on functionalgroups and Pt oxide present on the surface ofdifferent Pt/C catalysts

In an impact evaluation of the adjusted hydrophilicity of catalyst surface, achieved through the proprietary
surface treatment, on the dispersion and durability of ionomers, excessively hydrophilic Pt/C catalysts
demonstrated poor ionomer dispersion and reduced gas diffusivity due to water accumulation. Pt/C
catalysts for which the hydrophilicity was controlled so that they had decreased hydrophilic properties, on
the other hand, exhibited optimal ionomer dispersibility (Figure 3) and superior I-V performance.
Additionally, in a water-generating load cycle test conducted under the conditions that mirrored the actual
operating conditions, Pt/C catalysts with controlled and moderately-reduced hydrophilicity appropriate
were found to have appropriate wettability, which resulted in improved durability compared to excessivelyhydrophilic Pt/C catalysts.

Figure 3. Observation of ionomer dispersion on surfaces ofdifferent Pt/C catalysts

These results demonstrate that appropriately control of the surface state of catalysts helps optimize theMEA structure and enhance durability. They offer a potential indicator for more straightforward,
quantitative MEA optimization with respect to ionomer dispersion and durability based on catalyst
hydrophilicity.
For more details on the announcement, please visit the link:
https://pubs.acs.org/doi/10.1021/acsaem.3c01706/2/4

NEWS RELEAS

A 3D model depicting hydrophilic/hydrophobic state of catalyst surface■ Article published in: ACS Applied Energy Materials (November 27th, 2023 issue)* Online version available: November 9, 2023
■ Title of article: Impacts of Pt/Carbon Black Catalyst Surface Hydrophilicity on Ionomer Distribution andDurability during Water-Generating Load Cycling of Polymer Electrolyte Fuel Cells■ DOI: 10.1021acsaem.3c01706■ Abstract (PDF version) available on: https://pubs.acs.org/doi/10.1021/acsaem.3c01706
These are the results from joint research conducted by N.E. CHEMCAT CORPORATION and Professor
Makoto Uchida and his research group at Hydrogen and Fuel Cell Nanomaterials Center, University ofYamanashi.
■Coauthors
Makoto Uchida (Manager, Professor, Hydrogen and Fuel Cell Nanomaterials Center, University ofYamanashi)
Kayoko Tamoto (Hydrogen and Fuel Cell Nanomaterials Center)■Authors
Kiyotaka Nagamori (Group Leader, Fundamental Technology Department, R&D Center)
Satoshi Aoki (Fundamental Technology Department, R&D Center)
Mayumi Ikegawa (Fundamental Technology Department, R&D Center)Yuta Honda (Fundamental Technology Department, R&D Center)
Yasuhiro Seki (General Manager, Fundamental Technology Department, R&D Center)
Hiroshi Igarashi (Vice President, General Manager, R&D Center)■ Comment from co-author Professor Makoto Uchida at the University of Yamanashi
The performance of polymer electrolyte fuel cells (PEFCs) is influenced significantly by the structure of3/4

NEWS RELEAS

the MEAs and the dispersion of the ionomer.
In this study, we adjusted the hydrophilicity of commonly-used porous carbon-supported catalyst throughsurface treatment, and investigated how it influenced the dispersion and durability of the ionomer. Ourresults showed that decreased hydrophilic catalysts with moderate functional groups exhibited optimalionomer dispersibility and superior I-V performance.
In addition, durability tests using water-generating load cycles revealed that catalysts with decreasedhydrophilicity exhibited improved durability thanks to moderate wettability. Our findings suggest that byappropriately controlling the catalyst's surface conditions, we can enhance the MEA structure andimprove its performance and durability.
The groundbreaking aspects of this study include:(i) It proposes a straightforward method for evaluating the hydrophilicity of a catalyst layer;(ii) It involved power generation as part of durability evaluation, with the effects of water management on
durability taken into account in the analysis assessment; and(iii) It achieved a significant improvement of the performance and durability of widely-used carbonsupported catalysts through surface modification treatment; the study has drawn acclaim for this novel,advanced approach.
■ About N.E. CHEMCAT CORPORATION:
N.E. CHEMCAT CORPORATION is engaged in the development, manufacturing, and distribution ofchemical catalysts, auto exhaust catalysts (including three-way catalysts and diesel auto catalysts),
and fuel cell catalysts, and collection/refinement of precious metal catalysts.
[Head Office] 27th floor, World Trade Center Building South Tower, 2-4-1 Hamamatsucho, Minatoku, Tokyo 105-5127[Numazu Plant]] 678 Ipponmatsu, Numazu-City, Shizuoka-Prefecture 410-0314[Tsukuba Plant] 25-3, Kohshindaira, Bando-City, Ibaraki-Prefecture 306-0608[Representative] Susumu Endo, President & Representative Director[Foundation] April 1964
[Capital] 3.4235 billion yen[URL] https://www.ne-chemcat.co.jp/■ For inquiries on this release, please contact:
Public Relations, N.E. CHEMCAT CORPORATION; E-mail: info-pr@ne-chemcat.co.jp

4/4