scholarly journals An Iron(III) Complex with Pincer Ligand—Catalytic Water Oxidation through Controllable Ligand Exchange

Reactions ◽  
2020 ◽  
Vol 1 (1) ◽  
pp. 16-36
Author(s):  
Sahir M. Al-Zuraiji ◽  
Dávid Lukács ◽  
Miklós Németh ◽  
Krisztina Frey ◽  
Tímea Benkó ◽  
...  
Keyword(s):  
Indium Tin Oxide ◽  
Photoelectron Spectroscopy ◽  
Water Oxidation ◽  
Active Form ◽  
Oxidation Catalysis ◽  
Molecular Water ◽  
Pincer Ligands ◽  
Pincer Ligand ◽  
X Ray ◽  
Water Oxidation Catalysis

Pincer ligands occupy three coplanar sites at metal centers and often support both stability and reactivity. The five-coordinate [FeIIICl2(tia-BAI)] complex (tia-BAI− = 1,3-bis(2’-thiazolylimino)isoindolinate(−)) was considered as a potential pre-catalyst for water oxidation providing the active form via the exchange of chloride ligands to water molecules. The tia-BAI− pincer ligand renders water-insolubility to the Fe–(tia-BAI) assembly, but it tolerates the presence of water in acetone and produces electrocatalytic current in cyclic voltammetry associated with molecular water oxidation catalysis. Upon addition of water to [FeIIICl2(tia-BAI)] in acetone the changes in the Fe3+/2+ redox transition and the UV-visible spectra could be associated with solvent-dependent equilibria between the aqua and chloride complex forms. Immobilization of the complex from methanol on indium-tin-oxide (ITO) electrode by means of drop-casting resulted in water oxidation catalysis in borate buffer. The O2 detected by gas chromatography upon electrolysis at pH 8.3 indicates >80% Faraday efficiency by a TON > 193. The investigation of the complex/ITO assembly by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) before and after electrolysis, and re-dissolution tests suggest that an immobilized molecular catalyst is responsible for catalysis and de-activation occurs by depletion of the metal.

scholarly journals Effects of pH and Ca exchange on the structure and redox state of synthetic Na-birnessite

2021 ◽  
Vol 106 (1) ◽  
pp. 15-27
Author(s):  
Chiara Elmi ◽  
Jeffrey E. Post ◽  
Peter J. Heaney ◽  
Eugene S. Ilton
Keyword(s):  
Photoelectron Spectroscopy ◽  
Water Oxidation ◽  
Structure Refinement ◽  
Oxidation Catalysis ◽  
X Ray ◽  
Cell Parameters ◽  
Ph Values ◽  
Water Oxidation Catalysis ◽  
Effects Of Ph ◽  
End Members

Abstract Birnessite-like minerals are among the most common Mn oxides in surficial soils and sediments, and they mediate important environmental processes (e.g., biogeochemical cycles, heavy metal confinement) and have novel technological applications (e.g., water oxidation catalysis). Ca is the dominant interlayer cation in both biotic and abiotic birnessites, especially when they form in association with carbonates. The current study investigated the structures of a series of synthetic Ca-birnessite analogs prepared by cation-exchange with synthetic Na-birnessite at pH values from 2 to 7.5. The resulting Ca-exchanged birnessite phases were characterized using powder X-ray diffraction and Rietveld refinement, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning and transmission electron microscopy. All samples synthesized at pH values greater than 3 exhibited a similar triclinic structure with nearly identical unit-cell parameters. The samples exchanged at pH 2 and 3 yielded hexagonal structures, or mixtures of hexagonal and triclinic phases. Rietveld structure refinement and X-ray photoelectron spectroscopy showed that exchange of Na by Ca triggered reduction of some Mn3+, generating interlayer Mn2+ and vacancies in the octahedral layers. The triclinic and hexagonal Ca-birnessite structures described in this study were distinct from Na- and H-birnessite, respectively. Therefore, modeling X-ray absorption spectra of natural Ca-rich birnessites through mixing of Na- and H-birnessite end-members will not yield an accurate representation of the true structure.

scholarly journals Molecular water oxidation catalysis by zwitterionic carboxylate bridge-functionalized bis-NHC iridium complexes

2019 ◽  
Vol 9 (6) ◽  
pp. 1437-1450 ◽  
Author(s):  
Raquel Puerta-Oteo ◽  
M. Victoria Jiménez ◽  
Jesús J. Pérez-Torrente
Keyword(s):  
Water Oxidation ◽  
Oxidation Catalysis ◽  
Molecular Water ◽  
Iridium Complexes ◽  
Intermediate Species ◽  
Carboxylate Bridge ◽  
Water Oxidation Catalysis ◽  
High Valent

Carboxylate functionalized bis-NHC ligands allow for the stabilization of high-valent iridium intermediate species involved in homogeneous water oxidation catalysis.

Engineering Disorder at a Nanoscale: A Combined TEM and XAS Investigation of Amorphous versus Nanocrystalline Sodium Birnessite

2015 ◽  
Vol 68 (11) ◽  
pp. 1715 ◽  
Author(s):  
Rosalie K. Hocking ◽  
Hannah J. King ◽  
Aimee Hesson ◽  
Shannon A. Bonke ◽  
Bernt Johannessen ◽  
...  
Keyword(s):  
Water Oxidation ◽  
Nanocrystalline Material ◽  
Oxidation Catalysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Water Oxidation Catalysis ◽  
Catalytically Active ◽  
Amorphous Metal Oxide ◽  
X Ray Absorption

The term amorphous metal oxide is becoming widely used in the catalysis community. The term is generally used when there are no apparent peaks in an X-ray diffraction pattern. However, the absence of such features in X-ray diffraction can mean that the material is either truly amorphous or that it is better described as nanocrystalline. By coprecipitating a sodium birnessite-like phase with and without phosphate (1.5 %), we are able to engineer two very similar but distinct materials – one that is nanocrystalline and the other that is amorphous. The two closely related phases were characterized with both Mn K-edge X-ray absorption spectroscopy and high-resolution transmission electron microscopy. These structural results were then correlated with catalytic and electrocatalytic activities for water oxidation catalysis. In this case, the amorphous phosphate-doped material was less catalytically active than the nanocrystalline material.

scholarly journals High-Throughput Screening and Rational Design to Drive Discovery in Molecular Water Oxidation Catalysis

2021 ◽  
Author(s):  
Michael Craig ◽  
Max Garcia-Melchor
Keyword(s):  
Density Functional Theory ◽  
Water Oxidation ◽  
High Throughput Screening ◽  
Density Functional ◽  
Rational Design ◽  
Oxidation Catalysis ◽  
Molecular Water ◽  
Future Research ◽  
Functional Theory ◽  
Water Oxidation Catalysis

In this work we study a library of 444 hypothetical complexes for the OER composed of distinct metals (Cr, Mn, Fe, Ru, Co & Ni) and ligand skeletons. These were analysed using density functional theory via different functionals to drive interesting insights and suggestions for future research of this reaction.

scholarly journals Foot of the Wave Analysis for Mechanistic Elucidation and Benchmarking Applications in Molecular Water Oxidation Catalysis

ChemSusChem ◽  
2016 ◽  
Vol 9 (23) ◽  
pp. 3361-3369 ◽  
Author(s):  
Roc Matheu ◽  
Sven Neudeck ◽  
Franc Meyer ◽  
Xavier Sala ◽  
Antoni Llobet
Keyword(s):  
Water Oxidation ◽  
Oxidation Catalysis ◽  
Molecular Water ◽  
Wave Analysis ◽  
Water Oxidation Catalysis
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