Editorial Board Members’ Collection Series in “Water Oxidation Catalysts”

A special issue of Inorganics (ISSN 2304-6740). This special issue belongs to the section "Inorganic Solid-State Chemistry".

Deadline for manuscript submissions: closed (31 December 2023) | Viewed by 4330

Special Issue Editors


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Guest Editor
Department of Chemistry, Yale University, New Haven, CT 06520, USA
Interests: photosystem II; natural and artificial photosynthesis; Mn metalloproteins; water oxidation catalysis; EPR spectroscopy
Van 't Hoff Institute for Molecular Sciences—HIMS, University of Amsterdam, NL-1098 XH Amsterdam, The Netherlands
Interests: electrocatalysis; surface sciences; green synthesis; complex oxides; solid oxide fuel cells; water electrolysis
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Special Issue Information

Dear Colleagues,

Water oxidation is an essential reaction in providing reducing equivalents for solar fuel formation in both natural and artificial photosynthesis. Developing efficient and stable water oxidation catalysts (WOCs) is the key to constructing systems for storing solar energy in the form of chemical bonds, but it still faces enormous challenges from both fundamental and applied viewpoints. Numerous catalysts have been reported for both photo- and electro-catalytic water oxidation, some of which were inspired by nature’s oxygen-evolving complex in photosystem II. Other research directions concern the development of macromolecular and nano-materials, thin films, solid materials, and heterogenized molecular catalysts that can be tuned to optimize water oxidation chemistry, which unlocks the exciting interdisciplinary field of homogeneous and heterogeneous catalysis. This Special Issue aims to collect original research articles or comprehensive review papers focused on recent advances in the fundamentals and applications of water oxidation catalysts.

Prof. Dr. Gary Brudvig
Dr. Ning Yan
Guest Editors

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Keywords

  • water oxidation catalysts
  • water splitting
  • catalysts
  • artificial photosynthesis
  • molecular catalysts
  • heterogeneous catalysts
  • photo/electrochemistry
  • catalyst design
  • oxygen evolution

Published Papers (3 papers)

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Research

10 pages, 2047 KiB  
Article
Applicability of Transition State Theory to the (Proton-Coupled) Electron Transfer in Photosynthetic Water Oxidation with Emphasis on the Entropy of Activation
by Holger Dau and Paul Greife
Inorganics 2023, 11(10), 389; https://doi.org/10.3390/inorganics11100389 - 30 Sep 2023
Viewed by 1127
Abstract
Recent advancements in the study of the protein complex photosystem II have clarified the sequence of events leading to the formation of oxygen during the S3 → S4 → S0 transition, wherein the inorganic Mn4Ca(µ-O)6(OHx [...] Read more.
Recent advancements in the study of the protein complex photosystem II have clarified the sequence of events leading to the formation of oxygen during the S3 → S4 → S0 transition, wherein the inorganic Mn4Ca(µ-O)6(OHx)4 cluster finishes photo-catalyzing the water splitting reaction (Greife et al., Nature 2023, 617, 623–628; Bhowmick et al., Nature 2023, 617, 629–636). During this final step, a tyrosine radical (TyrZ), stable for a couple of milliseconds, oxidizes a cluster-bound oxygen while the hydrogen bonding patterns of nearby waters shift a proton away. A treatment of this redox reaction within the context of accepted transition state theories predicts rate constants that are significantly higher than experimentally recovered values (1012 s−1 versus 103 s−1). In an effort to understand this disparity, temperature-dependent experiments have revealed large entropic contributions to the rates with only a moderate enthalpy of activation. We suggest that the entropic source may be related to the observed proton rearrangements, and further possible near isoenergetic variations in the nearby extended H-bonding network delaying the realization of an ‘ideal’ transition state. In the following, we explore this relation in the context of Eyring’s transition state theory and Marcus’ electron transfer theory and evaluate their compatibility with the experimental evidence. Full article
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16 pages, 3048 KiB  
Article
Structure–Function Relationship within Cu-Peptoid Electrocatalysts for Water Oxidation
by Guilin Ruan, Natalia Fridman and Galia Maayan
Inorganics 2023, 11(7), 312; https://doi.org/10.3390/inorganics11070312 - 24 Jul 2023
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Abstract
Water oxidation (WO) is the first step in the water-splitting process aiming at the production of hydrogen as a green renewable fuel. To successfully perform WO, potent strategies for overcoming the high energetic barrier and slow kinetics of this reaction are urgently required. [...] Read more.
Water oxidation (WO) is the first step in the water-splitting process aiming at the production of hydrogen as a green renewable fuel. To successfully perform WO, potent strategies for overcoming the high energetic barrier and slow kinetics of this reaction are urgently required. One such strategy is the use of molecular catalysis. Specifically, Cu-based catalysts have been highlighted over the last decade due to their stability and fast kinetics. Among them, Cu-peptoids, where peptoids are peptidomimetics akin to peptides and are N-substituted glycine oligomers, can act as stable and active catalysts for oxidation transformations including electrocatalytic WO. Previously, we suggested that a benzyl group incorporated as a side chain near the catalytic site within a Cu-peptoid electrocatalyst for WO has a structural role in the activity of the electrocatalyst in phosphate buffer (PBS). Herein, we aimed to test this hypothesis and understand how an incorporated structural element side chain affects WO. To this aim, we prepared a set of peptoid trimers each with a different structural element replacing the benzyl group by either naphthyl, cyclohexyl, benzyl, propyl chloride, or propyl side chains as well as a peptoid lacking a structural element. We studied the structure of their Cu complexes and tested these complexes as electrocatalysts for WO. We discovered that while all the peptoids self-assemble to form dinuclear Cu-peptoid complexes, the duplex that has no structural side chain, Cu2(BE)2, is structurally different from the others in the solid state. Moreover, Cu2(BE)2 remains dinuclear in a PBS at pH 11, while all the other duplexes are mononuclear in the PBS. Finally, though most of the complexes showed low electrocatalytic activity for WO, the dinuclear complex Cu2(BE)2 performed with the highest turnover frequency of 484 s−1. Nevertheless, this dinuclear complex slowly decomposes to the corresponding mononuclear complex as a more stable species during WO, while the other mononuclear complexes retain their structure in solution but display much slower kinetics (ca. 5 to 8 s−1) under the same conditions. Overall, our results demonstrate that bulkier side chains hamper the stability of dinuclear Cu-peptoids in a PBS, and hence, their efficiency as WO electrocatalysts is also hampered. Full article
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11 pages, 2260 KiB  
Article
Ligand Tuning in Cu(pyalk)2 Water Oxidation Electrocatalysis
by Claire C. Cody, Zofia N. Caes, Matt D. Capobianco, Brandon Q. Mercado, Robert H. Crabtree and Gary W. Brudvig
Inorganics 2023, 11(6), 229; https://doi.org/10.3390/inorganics11060229 - 26 May 2023
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Abstract
Molecular copper water oxidation electrocatalysts have been extensively studied in recent years for their potential use in artificial photosynthetic systems for solar energy conversion. Although ligand modification and its ability to influence catalytic properties is a key advantage of molecular systems, there are, [...] Read more.
Molecular copper water oxidation electrocatalysts have been extensively studied in recent years for their potential use in artificial photosynthetic systems for solar energy conversion. Although ligand modification and its ability to influence catalytic properties is a key advantage of molecular systems, there are, as yet, few examples of systematic studies of these effects. Our oxidatively resistant pyalk (2-pyridyl-2-propanoate) ligand forms a complex with copper(II) that catalyzes water oxidation and provides an attractive scaffold for systematic ligand tuning. Here, we report a series of analogous copper complexes with electron-donating (methoxy-) and -withdrawing (methoxycarbonyl-) groups at the para-position of the pyalk ligand. Trends in the pKa and redox potential align with first-principles predictions for the electron-withdrawing and electron-donating groups. While the modified complexes show good activity for water oxidation, lowered faradaic efficiency in comparison to the parent complex highlights the importance of stability considerations for catalyst tuning. Full article
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