Oxygen Plasma Induced Nanochannels for Creating Bimetallic Hollow Nanocrystals

Oxygen Plasma Induced Nanochannels for Creating Bimetallic Hollow Nanocrystals

ACS Nano

10.1021/acsnano.3c06148

http://dx.doi.org/10.1021/acsnano.3c06148

Wen-Ya Wu, Sida Wu, Weng Weei Tjiu, Hui Ru Tan, Fong Yew Leong, Poh Chong Lim, Suxi Wang, Wenbin Jiang, Rong Ji, Qiang Zhu, Michel Bosman, Qingyu Yan, Zainul Aabdin

General Materials Science

23 August 2023

Wu, W.-Y., Wu, S., Tjiu, W. W., Tan, H. R., Leong, F. Y., Lim, P. C., Wang, S., Jiang, W., Ji, R., Zhu, Q., Bosman, M., Yan, Q., & Aabdin, Z. (2023). Oxygen Plasma Induced Nanochannels for Creating Bimetallic Hollow Nanocrystals. ACS Nano, 17(17), 17536–17544 (2023). https://doi.org/10.1021/acsnano.3c06148

Platinum-based metal catalysts are considered excellent catalytic converters that are especially effective in performing catalytic reactions in fuel cell catalytic reactions. For example, Ag/Pt alloys are known to be highly efficient as electrocatalysts for oxygen reduction reactions, such as the electro-oxidation of methanol. The atomic structure at the Pt surface and the Ag-Pt interface both influence the catalytic performance, controlling the efficiency in the electrochemical reactions. This work aims to understand the mechanism of changes to the Ag/Pt core/shell nanocrystals when undergoing oxygen plasma treatment. We carefully designed the oxidation treatment and investigated the structural and compositional evolution in the accelerated oxidation-triggered diffusion of Ag towards Pt. The oxygen plasma treatment produces a fast oxidative effect on the Ag atoms, leading to the Kirkendall effect. After prolonged oxygen plasma treatment, most core/shell nanocrystals evolve into hollow spheres. At the same time, a minor fraction remains unchanged in terms of morphology with a well-protected Ag core and a monocrystalline Pt shell. We hypothesise that the O2 plasma disturbs the Pt shell surface and introduces active O species that meet with the diffused Ag from the inside out. Based on EDX elemental mapping, combined with several electron microscopic techniques, we deduced the formation mechanism of the hollow structures to be: (I) the oxidation of Ag within the Pt lattice causes a disrupted crystal lattice of the Pt; (II) nanochannels arise at the defect locations on the Pt shell; (III) the remainder of the Ag atoms pass through these nanochannels and leave a hollow crystal behind. Our findings deepen the understanding of interface dynamics of bimetallic nanostructured catalysts under an oxidative environment and shine a light on a new approach for catalyst pre-treatment.

Publisher Copyright

This research / project is supported by the A*STAR - Career Development Award (CDA)
Grant Reference no. : 202D800032

This research / project is supported by the A*STAR - AME IAF-PP
Grant Reference no. : A20G1a0046

This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Nano, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see doi.org/10.1021/acsnano.3c06148

https://oar.a-star.edu.sg/communities-collections/articles/19853

1936-0851
1936-086X

Institute of Materials Research and Engineering