Ordered catalyst electrode research and application for PEM fuel cells

Yan, Yichang (2024). Ordered catalyst electrode research and application for PEM fuel cells. University of Birmingham. Ph.D.

This is the latest version of this item.

Yan2024PhD.pdf
Text - Accepted Version
Restricted to Repository staff only until 31 July 2028.
Available under License All rights reserved.
Download (7MB) | Request a copy

Abstract

Owing to their distinctive surface properties and stability, one-dimensional (1D) nanostructures are considered to be one of the promising avenues for the development of the next generation of proton exchange membrane fuel cells (PEMFCs). However, in comparison with conventional spherical Pt/C nanoparticle electrocatalysts, 1D nanostructures exhibit markedly different behaviour during fuel cell operation. This is attributable to their anisotropic morphology and unique surface structure. The paucity of related fundamental knowledge and detailed mechanisms presents a significant challenge in fabricating high-performance electrodes based on these structures. This PhD research focuses on the development of a novel three-dimensional (3D) ordered catalyst electrode design, predicated upon Pt nanowire arrays (Pt NWAs). It aims to establish a comprehensive understanding of the structure-power performance relationship to inform the development of PEMFCs suitable for high current density operation.
The catalyst electrode featuring a 3D-ordered catalyst layer is achieved through the introduction of a surface modification technique applied to gas diffusion layers (GDLs), thereby facilitating the fabrication of gas diffusion electrodes (GDEs). This is realised by sputtering gold nanoparticles onto the GDL surface to function as crystal seeds, which control the in-situ growth process, thereby forming uniformly distributed single crystal Pt NWAs. Utilising an equivalent thickness of 0.6 nm of Au nano seeds, the AuPt NWA GDE attains a power density of 1.45 W·cm-2, which is 32% higher than that of the GDE fabricated from commercial Pt/C catalyst. The durability of the Pt NWA GDE improves significantly, evidencing only a 43.0% decline after undergoing an accelerated stress test consisting of 42,000 potential cycles; this is in contrast to the 92.9% decline observed in the Pt/C GDE after 20,000 cycles. Subsequently, an orthogonal experiment is conducted to systematically elucidate the operational behaviours of this innovative Au-Pt NWA 3D-ordered electrode design, compared to Pt/C electrodes. The variables examined include temperature, back pressure, relative humidity, and cathode stoichiometry. The analysis reveals that the AuPt NWA GDE exhibits greater sensitivity to operational conditions and identifies back pressure as the most influential factor for performance enhancement.
Lastly, for the first time, a quantification study is carried out on the oxygen transport resistance associated with the 3D-ordered electrodes. This study aims to delineate the distinct contributions from bulk/molecular diffusion, Knudsen diffusion, and oxygen penetration through the ionomer layer on the catalyst surface

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):