Title: Insights into Copper Sulfide Formation from Cu and S K edge XAS and DFT studies

Abstract

An understanding of the fundamentals of the reaction between CuO with trace amounts of H₂S to form CuS products is critical for the optimal utilization of this process in sulfur removal applications. Unfortunately, CuS is a complex material, featuring various Cu_2-xS compounds (with 0 ≤ x ≤ 1), distorted crystal phases, and varying electronic structures and coordination environments of Cu and S ions. In this work, we combine ex situ and in situ X-ray absorption spectroscopy (XAS) at S and Cu K edges, fixed bed sorption experiments, DFT simulations, and other characterization techniques to speciate the CuS products formed at different temperatures (298–383 K) and from CuO sorbents with different crystallite sizes (2.8–40 nm). The results of our analysis identify the formation of a distorted CuS layer at the surface of CuO crystals with disulfide groups with shorter Cu–S bonds and higher delocalization of the positive charge of the Cu center into (S^1–)2. This distorted CuS layer dominates the XAS signal at lower temperatures (298–323 K) and at the initial stages of sulfidation at higher temperatures (353 and 383 K) where conversion is low (<40%). First-principles atomistic simulations confirm the thermodynamic favorability of the formation of surface (S^1–)2 on both CuO (111) and ($$\bar{1}11$$) surfaces, providing further support for our experimental observations. Furthermore, these simulations reveal that the presence of disulfide bonds stabilized surface hydroxyl groups, leading to lower Gibbs Free Energies of their surface migration.

Authors:

Azzam, Sara A. ^[1]; Boubnov, Alexey ^[2]; Hoffman, Adam S. ^[3]; López-Ausens, Tirso ^[1]; Chiang, Nicole ^[1]; Canning, Griffin ^[4]; Sautet, Philippe  ^[1];

• Search DOE PAGES for author "Sautet, Philippe"
• Search DOE PAGES for ORCID "0000-0002-8444-3348"

Bare, Simon R. ^[3]; Simonetti, Dante A.  ^[5]

• Search DOE PAGES for author "Simonetti, Dante A."
• Search DOE PAGES for ORCID "0000-0002-5708-460X"

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+ Show Author Affiliations

1. Univ. of California, Los Angeles, CA (United States)
2. SLAC National Accelerator Lab., Menlo Park, CA (United States); Karlsruhe Inst. of Technology (KIT) (Germany)
3. SLAC National Accelerator Lab., Menlo Park, CA (United States)
4. Univ. of New Mexico, Albuquerque, NM (United States)
5. Univ. of California, Los Angeles, CA (United States); Institute for Carbon Management (ICM), Los Angeles, CA (United States)

Publication Date:

Thu Oct 01 00:00:00 EDT 2020

Research Org.:

SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1769621

Grant/Contract Number:  

AC02-76SF00515; EEC-1647722; 56978-DNI5

Resource Type:

Accepted Manuscript

Journal Name:

Inorganic Chemistry

Additional Journal Information:

Journal Volume: 59; Journal Issue: 20; Journal ID: ISSN 0020-1669

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; X-ray absorption near edge spectroscopy; Extended X-ray absorption fine structure; Chemical reactions; Sorbents; Materials