Theoretical Investigation of the Hydrogenation of Cyclohexene Catalyzed by Supported Single-Atom Sites on Redox Noninnocent LiMn₂O₄ and Li₂Mn₂O₄ Surfaces

Journal Article · 18 March 2024 · Journal of Physical Chemistry. C

DOI: https://doi.org/10.1021/acs.jpcc.4c00284 · OSTI ID:2403300

Xu, Jiayi  ^[1]; Patel, Prajay  ^[2]; Kropf, A. Jeremy  ^[1]; Kaphan, David  ^[1]; Delferro, Massimiliano  ^[1]; Liu, Cong  ^[1]

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1. Argonne National Laboratory (ANL), Argonne, IL (United States)
2. Argonne National Laboratory (ANL), Argonne, IL (United States); Univ. of Dallas, Irving, TX (United States)

Here, the tuning of catalyst activity via stereoelectronic modulation of the active-site structure remains a grand challenge in heterogeneous catalysis. In homogeneous catalysis, the redox noninnocent ligands can be introduced to organometallic fragments to donate electrons to the metal center and fine-tune the catalytic activity. Analogously, lithium-ion battery materials, such as lithium manganese oxide (LMO), lithium titanium oxides (LTO), etc., can serve as redox noninnocent catalyst support to modulate the electronic structures of the active site via lithiation, hence tuning the catalytic activity of supported active sites. Experimentally, the Ni single-atom site was supported on LiMn₂O₄ via oxidative grafting and exhibited no catalytic activity toward the hydrogenation of cyclohexene. After introducing additional Li into the catalyst support forming Li₂Mn₂O₄, the Ni single-atom site becomes active, with the catalytic rates increasing as a function of the lithiation for Li/Mn ratios >0.9. In this paper, density functional theory (DFT) calculations are performed to study the Ni site structure via X-ray absorption near edge structure (XANES) simulations and investigate the electronic properties of Ni single-atom site before and after the addition of intercalated lithium in the LMO spinel structure. Furthermore, the study of the reaction mechanism is also carried out to understand the thermodynamically and kinetically favored pathways. XANES simulation suggests that the Ni single-atom site is likely to stay in the Li channel of the spinel support structure and form an octahedral structure. After Li intercalation, the Ni site becomes less positively charged, indicating the partial reduction of the Ni site. The simulated reaction energy profile over the LiMn₂O₄ support exhibits high-energy barriers (1.07 eV) for the hydrogenation of cyclohexene; however, the Li₂Mn₂O₄ support is able to better stabilize low-coordinated ion sites and improve ion mobility, leading to lower overall energy barriers (0.64 eV). The reduced and low-coordinated ion site, thus, can better stabilize the reaction intermediates and promote hydrogenation reaction. Similarly, other transition metal ions (Fe, Co, and Cu) are also considered over the LiMn₂O₄ and Li₂Mn₂O₄ catalyst supports for hydrogenation reaction.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division (CSGB)
• Grant/Contract Number: AC02-06CH11357; AC02-05CH11231
• OSTI ID: 2403300
• Journal Information: Journal of Physical Chemistry. C, Journal Name: Journal of Physical Chemistry. C Journal Issue: 12 Vol. 128; ISSN 1932-7447
• Publisher: American Chemical SocietyCopyright Statement
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Atomically Dispersed Catalyst
Density Functional Theory
Hydrogenation Reaction
Redox Non-Innocent Support
XANES Simulation