scholarly journals Lithium Ion Battery Materials as Tunable, Redox Non-Innocent Catalyst Supports

2021 ◽  
Author(s):  
Alon Chapovetsky ◽  
Ryan J. Witzke ◽  
Robert Kennedy ◽  
Evan Wegener ◽  
Fulya Dogan ◽  
...  
Keyword(s):  
Lithium Ion ◽  
Catalyst Supports ◽  
Paramagnetic Resonance ◽  
Battery Materials ◽  
X Ray ◽  
Electronic Tuning ◽  
Microscopy Techniques ◽  
Nickel Species ◽  
X Ray Absorption ◽  
Electron Paramagnetic

The development of general strategies for the electronic tuning of a catalyst’s active site is an ongoing challenge in heterogeneous catalysis. To this end we report the application of cathode and anode materials as redox non-innocent catalyst supports that can be continuously modulated as a function of lithium intercalation. A zero valent nickel complex was oxidatively grafted onto the surface of lithium manganese oxide (Li<sub>x</sub>Mn<sub>2</sub>O<sub>4</sub>) to yield single-sites of Ni<sup>2</sup><sub>­</sub><sup>+</sup> (Ni/Li<sub>x</sub>Mn<sub>2</sub>O<sub>4</sub>). Its activity for olefin hydrogenation was found to be a function of the redox state of the support material, with the most lithiated variant showing the most activity. X-ray absorption, X-ray photoelectron, solid-state nuclear magnetic resonance and electron paramagnetic resonance spectroscopies, and electron microscopy techniques established the nature of the nickel species on Li<sub>x</sub>Mn<sub>2</sub>O<sub>4</sub>. Catalyst control through support redox non-innocence was extended to an organotantalum complex on lithium titanium oxide (Li<sub>x</sub>TiO<sub>2</sub>), demonstrating the generality of this phenomenon.

scholarly journals Lithium Ion Battery Materials as Tunable, Redox Non-Innocent Catalyst Supports

2021 ◽  
Author(s):  
Alon Chapovetsky ◽  
Ryan J. Witzke ◽  
Robert Kennedy ◽  
Evan Wegener ◽  
Fulya Dogan ◽  
...  
Keyword(s):  
Lithium Ion ◽  
Catalyst Supports ◽  
Paramagnetic Resonance ◽  
Battery Materials ◽  
X Ray ◽  
Electronic Tuning ◽  
Microscopy Techniques ◽  
Nickel Species ◽  
X Ray Absorption ◽  
Electron Paramagnetic

The development of general strategies for the electronic tuning of a catalyst’s active site is an ongoing challenge in heterogeneous catalysis. To this end we report the application of cathode and anode materials as redox non-innocent catalyst supports that can be continuously modulated as a function of lithium intercalation. A zero valent nickel complex was oxidatively grafted onto the surface of lithium manganese oxide (Li<sub>x</sub>Mn<sub>2</sub>O<sub>4</sub>) to yield single-sites of Ni<sup>2</sup><sub>­</sub><sup>+</sup> (Ni/Li<sub>x</sub>Mn<sub>2</sub>O<sub>4</sub>). Its activity for olefin hydrogenation was found to be a function of the redox state of the support material, with the most lithiated variant showing the most activity. X-ray absorption, X-ray photoelectron, solid-state nuclear magnetic resonance and electron paramagnetic resonance spectroscopies, and electron microscopy techniques established the nature of the nickel species on Li<sub>x</sub>Mn<sub>2</sub>O<sub>4</sub>. Catalyst control through support redox non-innocence was extended to an organotantalum complex on lithium titanium oxide (Li<sub>x</sub>TiO<sub>2</sub>), demonstrating the generality of this phenomenon.

scholarly journals [FeFe]-Hydrogenase Maturation: H-Cluster Assembly Intermediates Tracked by Electron Paramagnetic Resonance, Infrared, and X-Ray Absorption Spectroscopy

2020 ◽  
Author(s):  
Brigitta Németh ◽  
Moritz Senger ◽  
Holly J. Redman ◽  
Pierre Ceccaldi ◽  
Joan Broderick ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Absorption Spectroscopy ◽  
Cluster Assembly ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Hydrogenase Maturation ◽  
Catalytically Active ◽  
X Ray Absorption ◽  
Electron Paramagnetic

[FeFe]-hydrogenase enzymes employ a unique organometallic cofactor for efficient and reversible hydrogen conversion. This so-called H-cluster consists of a [4Fe-4S] cubane cysteine-linked to a diiron complex coordinated by carbon monoxide and cyanide ligands and an azadithiolate ligand (adt = NH(CH2S)2). [FeFe]-hydrogenase apo-protein binding only the [4Fe-4S] sub-complex can be fully activated in vitro by the addition of a synthetic diiron site precursor complex ([2Fe]adt,). Elucidation of the mechanism of cofactor assembly will aid in the design of improved hydrogen processing synthetic catalysts. We combined in situ electron paramagnetic resonance, Fourier-transform infrared, and X-ray absorption spectroscopy to characterize intermediates of H-cluster assembly as initiated by mixing of the apo-protein (HydA1) from the green alga Chlamydomonas reinhardtii with [2Fe]adt. The three methods consistently show rapid formation of a complete H-cluster in the oxidized, CO-inhibited state (Hox-CO) already within seconds after the mixing. Moreover, FTIR spectroscopy support a model in which Hox-CO formation is preceded by a short-lived Hred´-CO like intermediate. Accumulation of Hox-CO was followed by CO release resulting in the slower conversion to the catalytically active state (Hox) as well as formation of reduced states of the H-cluster.

Lithium superoxide encapsulated in a benzoquinone anion matrix

2021 ◽  
Vol 118 (51) ◽  
pp. e2019392118
Author(s):  
Matthew Nava ◽  
Shiyu Zhang ◽  
Katharine S. Pastore ◽  
Xiaowen Feng ◽  
Kyle M. Lancaster ◽  
...  
Keyword(s):  
Solid State ◽  
Lithium Ion ◽  
Spectroscopic Characterization ◽  
Blue Color ◽  
Paramagnetic Resonance ◽  
Deep Blue ◽  
Lithium Peroxide ◽  
X Ray Absorption ◽  
Electron Paramagnetic ◽  
Lithium Air Batteries

Lithium peroxide is the crucial storage material in lithium–air batteries. Understanding the redox properties of this salt is paramount toward improving the performance of this class of batteries. Lithium peroxide, upon exposure to p–benzoquinone (p–C6H4O2) vapor, develops a deep blue color. This blue powder can be formally described as [Li2O2]0.3 · [LiO2]0.7 · {Li[p–C6H4O2]}0.7, though spectroscopic characterization indicates a more nuanced structural speciation. Infrared, Raman, electron paramagnetic resonance, diffuse-reflectance ultraviolet-visible and X-ray absorption spectroscopy reveal that the lithium salt of the benzoquinone radical anion forms on the surface of the lithium peroxide, indicating the occurrence of electron and lithium ion transfer in the solid state. As a result, obligate lithium superoxide is formed and encapsulated in a shell of Li[p–C6H4O2] with a core of Li2O2. Lithium superoxide has been proposed as a critical intermediate in the charge/discharge cycle of Li–air batteries, but has yet to be isolated, owing to instability. The results reported herein provide a snapshot of lithium peroxide/superoxide chemistry in the solid state with redox mediation.

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