Elucidating the formation and structural evolution of platinum single-site catalysts for the hydrogen evolution reaction

Tang, P; Lee, H; Hurlbutt, K; Huang, P; Narayanan, S; Wang, C; Gianolio, D; Arrigo, R; Chen, J; Warner, J; Pasta, M

Abstract

Platinum single-site catalysts (SSCs) are a promising technology for
the production of hydrogen from clean energy sources. They have high activity and
maximal platinum-atom utilization. However, the bonding environment of
platinum during operation is poorly understood. In this work, we present a
mechanistic study of platinum SSCs using operando, synchrotron-X-ray absorption
spectroscopy. We synthesize an atomically dispersed platinum complex with aniline
and chloride ligands onto graphene and characterize it with ex-situ electron
microscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, X-ray
absorption near-edge structure spectroscopy (XANES), and extended X-ray
absorption fine structure spectroscopy (EXAFS). Then, by operando EXAFS and
XANES, we show that as a negatively biased potential is applied, the Pt−N bonds break first followed by the Pt−Cl bonds. The
platinum is reduced from platinum(II) to metallic platinum(0) by the onset of the hydrogen-evolution reaction at 0 V. Furthermore,
we observe an increase in Pt−Pt bonding, indicating the formation of platinum agglomerates. Together, these results indicate that
while aniline is used to prepare platinum SSCs, the single-site complexes are decomposed and platinum agglomerates at operating
potentials. This work is an important contribution to the understanding of the evolution of bonding environment in SSCs and
provides some molecular insights into how platinum agglomeration causes the deactivation of SSCs over time.

• Journal Article Type: Article
• Acceptance Date: Feb 4, 2022
• Online Publication Date: Feb 23, 2022
• Publication Date: Feb 23, 2022
• Deposit Date: May 9, 2022
• Publicly Available Date: Jul 27, 2022
• Journal: ACS Catalysis
• Electronic ISSN: 2155-5435
• Publisher: American Chemical Society
• Volume: 12
• Issue: 5
• Pages: 3173-3180
• DOI: https://doi.org/10.1021/acscatal.1c05958
• Keywords: Catalysis, General Chemistry
• Publisher URL: https://doi.org/10.1021/acscatal.1c05958
• Related Public URLs: https://pubs.acs.org/
• Additional Information: Additional Information : This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in ACS Catalysis, copyright © 2022 American Chemical Society after peer review. To access the final edited and published work see https://pubs.acs.org/doi/abs/10.1021/acscatal.1c05958; Funders : Jiangsu Industrial Technology Research Institute; Projects : unspecified