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Liu, T., Zhan, S., Shen, N., Wang, L., Szabo, Z., Yang, H., . . . Sun, L. (2023). Bioinspired Active Site with a Coordination-Adaptive Organosulfonate Ligand for Catalytic Water Oxidation at Neutral pH. Journal of the American Chemical Society, 145(21), 11818-11828
Open this publication in new window or tab >>Bioinspired Active Site with a Coordination-Adaptive Organosulfonate Ligand for Catalytic Water Oxidation at Neutral pH
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2023 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 145, no 21, p. 11818-11828Article in journal (Refereed) Published
Abstract [en]

Many enzymes use adaptive frameworks to preorganize substrates, accommodate various structural and electronic demands of intermediates, and accelerate related catalysis. Inspired by biological systems, a Ru-based molecular water oxidation catalyst containing a configurationally labile ligand [2,2′:6′,2″-terpyridine]-6,6″-disulfonate was designed to mimic enzymatic framework, in which the sulfonate coordination is highly flexible and functions as both an electron donor to stabilize high-valent Ru and a proton acceptor to accelerate water dissociation, thus boosting the catalytic water oxidation performance thermodynamically and kinetically. The combination of single-crystal X-ray analysis, various temperature NMR, electrochemical techniques, and DFT calculations was utilized to investigate the fundamental role of the self-adaptive ligand, demonstrating that the on-demand configurational changes give rise to fast catalytic kinetics with a turnover frequency (TOF) over 2000 s–1, which is compared to oxygen-evolving complex (OEC) in natural photosynthesis. 

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2023
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-327110 (URN)10.1021/jacs.3c03415 (DOI)001011072400001 ()37196315 (PubMedID)2-s2.0-85160751257 (Scopus ID)
Funder
Swedish Research Council, 2017-00935
Note

QC 20230523

Available from: 2023-05-19 Created: 2023-05-19 Last updated: 2024-03-15Bibliographically approved
Yang, H., Liu, Y., Ding, Y., Li, F., Wang, L., Cai, B., . . . Sun, L. (2023). Monolithic FAPbBr3 photoanode for photoelectrochemical water oxidation with low onset-potential and enhanced stability. Nature Communications, 14(1), Article ID 5486.
Open this publication in new window or tab >>Monolithic FAPbBr3 photoanode for photoelectrochemical water oxidation with low onset-potential and enhanced stability
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2023 (English)In: Nature Communications, E-ISSN 2041-1723, Vol. 14, no 1, article id 5486Article in journal (Refereed) Published
Abstract [en]

Despite considerable research efforts on photoelectrochemical water splitting over the past decades, practical application faces challenges by the absence of efficient, stable, and scalable photoelectrodes. Herein, we report a metal-halide perovskite-based photoanode for photoelectrochemical water oxidation. With a planar structure using mesoporous carbon as a hole-conducting layer, the precious metal-free FAPbBr3 photovoltaic device achieves 9.2% solar-to-electrical power conversion efficiency and 1.4 V open-circuit voltage. The photovoltaic architecture successfully applies to build a monolithic photoanode with the FAPbBr3 absorber, carbon/graphite conductive protection layers, and NiFe catalyst layers for water oxidation. The photoanode delivers ultralow onset potential below 0 V versus the reversible hydrogen electrode and high applied bias photon-to-current efficiency of 8.5%. Stable operation exceeding 100 h under solar illumination by applying ultraviolet-filter protection. The photothermal investigation verifies the performance boost in perovskite photoanode by photothermal effect. This study is significant in guiding the development of photovoltaic material-based photoelectrodes for solar fuel applications.

Place, publisher, year, edition, pages
Springer Nature, 2023
National Category
Materials Chemistry Physical Chemistry Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-337792 (URN)10.1038/s41467-023-41187-9 (DOI)001065300300024 ()37679329 (PubMedID)2-s2.0-85170192499 (Scopus ID)
Note

QC 20231009

Available from: 2023-10-09 Created: 2023-10-09 Last updated: 2024-03-15Bibliographically approved
Liu, T. & Sun, L. (2023). Proton transfer regulating in catalytic water oxidation by Ru-complexes: second coordination sphere and beyond. Science Bulletin, 68(9), 854-856
Open this publication in new window or tab >>Proton transfer regulating in catalytic water oxidation by Ru-complexes: second coordination sphere and beyond
2023 (English)In: Science Bulletin, ISSN 2095-9273, Vol. 68, no 9, p. 854-856Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Elsevier BV, 2023
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-326690 (URN)10.1016/j.scib.2023.04.012 (DOI)001001241900001 ()37059664 (PubMedID)2-s2.0-85152291624 (Scopus ID)
Note

QC 20230626

Available from: 2023-05-08 Created: 2023-05-08 Last updated: 2023-06-26Bibliographically approved
Yang, H., Li, F., Zhan, S., Liu, Y., Li, W., Meng, Q., . . . Sun, L. (2022). Intramolecular hydroxyl nucleophilic attack pathway by a polymeric water oxidation catalyst with single cobalt sites. Nature Catalysis, 5(5), 414-429
Open this publication in new window or tab >>Intramolecular hydroxyl nucleophilic attack pathway by a polymeric water oxidation catalyst with single cobalt sites
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2022 (English)In: Nature Catalysis, ISSN 2520-1158, Vol. 5, no 5, p. 414-429Article in journal (Refereed) Published
Abstract [en]

Exploration of efficient water oxidation catalysts (WOCs) is the primary challenge in conversion of renewable energy into fuels. Here we report a molecularly well-defined heterogeneous WOC with Aza-fused, pi-conjugated, microporous polymer (Aza-CMP) coordinated single cobalt sites (Aza-CMP-Co). The single cobalt sites in Aza-CMP-Co exhibited superior activity under alkaline and near-neutral conditions. Moreover, the molecular nature of the isolated catalytic sites makes Aza-CMP-Co a reliable model for studying the heterogeneous water oxidation mechanism. By a combination of experimental and theoretical results, a pH-dependent nucleophilic attack pathway for O-O bond formation was proposed. Under alkaline conditions, the intramolecular hydroxyl nucleophilic attack (IHNA) process with which the adjacent -OH group nucleophilically attacks Co4+=O was identified as the rate-determining step. This process leads to lower activation energy and accelerated kinetics than those of the intermolecular water nucleophilic attack (WNA) pathway. This study provides significant insights into the crucial function of electrolyte pH in water oxidation catalysis and enhancement of water oxidation activity by regulation of the IHNA pathway.

Place, publisher, year, edition, pages
Springer Nature, 2022
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-313755 (URN)10.1038/s41929-022-00783-6 (DOI)000801852700013 ()2-s2.0-85130755520 (Scopus ID)
Note

QC 20220613

Available from: 2022-06-13 Created: 2022-06-13 Last updated: 2024-03-15Bibliographically approved
Liu, T., Li, G., Shen, N., Wang, L., Timmer, B., Zhou, S., . . . Sun, L. (2022). Isolation and Identification of Pseudo Seven-Coordinate Ru(III) Intermediate Completing the Catalytic Cycle of Ru-bda Type of Water Oxidation Catalysts. CCS Chemistry, 4(7), 2481-2490
Open this publication in new window or tab >>Isolation and Identification of Pseudo Seven-Coordinate Ru(III) Intermediate Completing the Catalytic Cycle of Ru-bda Type of Water Oxidation Catalysts
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2022 (English)In: CCS Chemistry, ISSN 2096-5745, Vol. 4, no 7, p. 2481-2490Article in journal (Refereed) Published
Abstract [en]

Isolation of RuIII-bda (17-electron specie) complex with an aqua ligand (2-electron donor) is challenging due to violation of the 18-electron rule. Although considerable efforts have been dedicated to mechanistic studies of water oxidation by the Ru-bda family, the structure and initial formation of the RuIII-bda aqua complex are still controversial. Herein, we challenge this often overlooked step by designing a pocket-shape Ru-based complex 1. The computational studies showed that 1 possesses the crucial hydrophobicity at the RuV(O) state as well as similar probability of access of terminal O to solvent water molecules when compared with classic Ru-bda catalysts. Through characterization of single-crystal structures at the RuII and RuIII states, a pseudo seven-coordinate “ready-to-go” aqua ligand with RuIII...O distance of 3.62 Å was observed. This aqua ligand was also found to be part of a formed hydrogen-bonding network, providing a good indication of how the RuIII-OH2 complex is formed.

Place, publisher, year, edition, pages
Chinese Chemical Society, 2022
Keywords
pseudo seven-coordinate, Ru-bda, RuIII-OH2 intermediate, water oxidation, water preorganization
National Category
Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-302712 (URN)10.31635/ccschem.021.202101159 (DOI)000826468400028 ()2-s2.0-85135170722 (Scopus ID)
Note

QC 20220811

Available from: 2021-09-29 Created: 2021-09-29 Last updated: 2024-03-18Bibliographically approved
Liu, T. (2022). Outer Coordination Spheres Engineering of Ru-based Molecular Water Oxidation Catalysts. (Doctoral dissertation). Stockholm: KTH Royal Institute of Technology
Open this publication in new window or tab >>Outer Coordination Spheres Engineering of Ru-based Molecular Water Oxidation Catalysts
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The outer coordination sphere plays a vital role in metalloenzyme catalysis, while this principle is relatively less considered in the design of man-made molecular catalysts. This thesis investigates the role of outer coordination spheres in water oxidation by a series of ruthenium-based complexes.

The first chapter presents an overview of the development of molecular water oxidation catalysts, mainly focusing on ruthenium-based complexes. Moreover, the strategies used to modulate the inner and outer coordination spheres are also summarized.

The second chapter clarifies the role of electronic effects and hydrophobic interactions in Ru-bda-type catalysts. Electronic effects are found to be the less-dominating parameter for the catalytic activity and mechanism, while hydrophobic interactions play an important role in catalysis. The third chapter focuses on the switch in mechanism with Ru-pda-type catalysts through strengthening of the π-π interactions between the axial ligands.

The fourth chapter discusses a crystal structure of the long-proposed pseudo-seven-coordinate RuIII-aqua complex where the aqua ligand is stabilized by the distal ligand. The obtained complex enables us to visualize how the catalyst grasps the incoming aqua ligands at the initial catalytic step. Based on this catalytic model, four catalysts with well-defined outer coordination spheres are synthesized, and the influence of hydrophilic/hydrophobic outer spheres on water oxidation is discussed in chapter five.

In general, this thesis follows the transition of the outer coordination sphere engineering from coordinated ligand modifications to remote substituent modulations.

Abstract [sv]

Den yttre koordinationssfären spelar en viktig roll i metalloenzymkatalys, medan principen är relativt mindre beaktad vid utformningen av konstgjorda molekylära katalysatorer. Denna avhandling undersöker rollen av yttre koordinationssfärer i vattenoxidation för en serie ruteniumbaserade komplex.

Det första kapitlet presenterar en översikt över utvecklingen av molekylära vattenoxidationskatalysatorer, främst med fokus på ruteniumbaserade komplex. Dessutom sammanfattas de strategier som används för att modulera de inre och yttre koordinationssfärerna.

Det andra kapitlet klargör rollen av elektroniska effekter och hydrofoba interaktioner i katalysatorer av Ru-bda-typ. Elektroniska effekter har visat sig vara den mindre dominerande parametern för den katalytiska aktiviteten och mekanismen, medan hydrofoba interaktioner spelar en viktig roll i katalys. Det tredje kapitlet fokuserar på ändringen i mekanismen för Ru-pda-typ katalysatorer genom förstärkning av π-π-interaktionerna mellan de axiella liganderna.

Det fjärde kapitlet diskuterar en kristallstruktur av det länge föreslagna pseudo-sju-koordinerade RuIII-vatten-komplexet där vattenliganden stabiliseras av den distala liganden. Det erhållna komplexet gör det möjligt att visualisera hur katalysatorn tar tag i de inkommande vattenliganderna vid det initiala katalytiska steget. Baserat på denna katalytiska modell syntetiseras fyra katalysatorer med väldefinierade yttre koordinationssfärer, och hydrofila/hydrofoba yttre sfärers påverkan på vattenoxidation diskuteras i kapitel fem.

I allmänhet följer denna avhandling övergången av den yttre koordinationssfärens konstruktion från koordinerade ligandmodifikationer till avlägsna substituentmoduleringar.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2022. p. 63
Series
TRITA-CBH-FOU ; 2022:23
Keywords
solar fuels, water oxidation, catalysis, ruthenium complex, Ru-bda, Ru-pda, outer coordination sphere, hydrophobic interactions
National Category
Organic Chemistry
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-309607 (URN)978-91-8040-174-6 (ISBN)
Public defence
2022-04-08, F3, Lindstedsvägen 26, Zoom: https://kth-se.zoom.us/j/65578340573, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 2022-03-08

Available from: 2022-03-08 Created: 2022-03-07 Last updated: 2022-06-25Bibliographically approved
Liu, T., Li, G., Shen, N., Wang, L., Timmer, B., Kravchenko, A., . . . Sun, L. (2022). Promoting Proton Transfer and Stabilizing Intermediates in Catalytic Water Oxidation via Hydrophobic Outer Sphere Interactions. Chemistry - A European Journal
Open this publication in new window or tab >>Promoting Proton Transfer and Stabilizing Intermediates in Catalytic Water Oxidation via Hydrophobic Outer Sphere Interactions
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2022 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765Article in journal (Other academic) Published
Abstract [en]

The outer coordination sphere of metalloenzyme often plays an important role in its high catalytic activity, however, this principle is rarely considered in the design of man-made molecular catalysts. Herein, four Ru-bda based molecular water oxidation catalysts with well-defined outer spheres are designed and synthesized. Experimental and theoretical studies showed that the hydrophobic environment around the Ru center could lead to thermodynamic stabilization of the high-valent intermediates and kinetic acceleration of the proton transfer process during catalytic water oxidation. By this outer sphere stabilization, a 6-fold rate increase for water oxidation catalysis has been achieved. 

Keywords
water oxidation; outer sphere; third coordination sphere; proton transfer; hydrophobicity; intermediates
National Category
Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-308969 (URN)10.1002/chem.202104562 (DOI)000772517600001 ()35289447 (PubMedID)2-s2.0-85126980836 (Scopus ID)
Note

QC 20220223

Available from: 2022-02-17 Created: 2022-02-17 Last updated: 2024-03-15Bibliographically approved
Liu, T. & Sun, L. (2022). The future challenges in molecular water oxidation catalysts. Journal of Energy Chemistry, 73, 643-645
Open this publication in new window or tab >>The future challenges in molecular water oxidation catalysts
2022 (English)In: Journal of Energy Chemistry, ISSN 2095-4956, E-ISSN 2096-885X, Vol. 73, p. 643-645Article in journal, Editorial material (Refereed) Published
Place, publisher, year, edition, pages
Elsevier BV, 2022
National Category
Chemical Process Engineering Other Materials Engineering Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-319844 (URN)10.1016/j.jechem.2022.07.001 (DOI)000855247600011 ()2-s2.0-85134934348 (Scopus ID)
Note

QC 20230515

Available from: 2022-10-10 Created: 2022-10-10 Last updated: 2023-05-25Bibliographically approved
Wang, L., Zhang, F., Liu, T., Zhang, W., Li, Y., Cai, B., . . . Sun, L. (2021). A crosslinked polymer as dopant-free hole-transport material for efficient n-i-p type perovskite solar cells. Journal of Energy Chemistry, 55, 211-218
Open this publication in new window or tab >>A crosslinked polymer as dopant-free hole-transport material for efficient n-i-p type perovskite solar cells
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2021 (English)In: Journal of Energy Chemistry, ISSN 2095-4956, E-ISSN 2096-885X, Vol. 55, p. 211-218Article in journal (Refereed) Published
Abstract [en]

A new crosslinked polymer, called P65, with appropriate photo-electrochemical, opto-electronic, and thermal properties, has been designed and synthesized as an efficient, dopant-free, hole-transport material (HTM) for n-i-p type planar perovskite solar cells (PSCs). P65 is obtained from a low-cost and easily synthesized spiro[fluorene-9,9′-xanthene]-3′,6′-diol (SFX-OH)-based monomer X65 through a free-radical polymerization reaction. The combination of a three-dimensional (3D) SFX core unit, hole-transport methoxydiphenylamine group, and crosslinked polyvinyl network provides P65 with good solubility and excellent film-forming properties. By employing P65 as a dopant-free hole-transport layer in conventional n-i-p type PSCs, a power conversion efficiency (PCE) of up to 17.7% is achieved. To the best of our knowledge, this is the first time a 3D, crosslinked, polymeric dopant-free HTM has been reported for use in conventional n-i-p type PSCs. This study provides a new strategy for the future development of a 3D crosslinked polymeric dopant-free HTM with a simple synthetic route and low-cost for commercial, large-scale applications in future PSCs.

Place, publisher, year, edition, pages
Elsevier BV, 2021
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-279565 (URN)10.1016/j.jechem.2020.06.062 (DOI)000605332900007 ()2-s2.0-85088262081 (Scopus ID)
Note

QC 20201028

Available from: 2020-08-25 Created: 2020-08-25 Last updated: 2023-05-25Bibliographically approved
Timmer, B., Kravchenko, O., Zhang, B., Liu, T. & Sun, L. (2021). Electronic Influence of the 2,2 '-Bipyridine-6,6 '-dicarboxylate Ligand in Ru-Based Molecular Water Oxidation Catalysts. Inorganic Chemistry, 60(2), 1203-1208
Open this publication in new window or tab >>Electronic Influence of the 2,2 '-Bipyridine-6,6 '-dicarboxylate Ligand in Ru-Based Molecular Water Oxidation Catalysts
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2021 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 60, no 2, p. 1203-1208Article in journal (Refereed) Published
Abstract [en]

Water provides an ideal source for the production of protons and electrons required for generation of renewable fuels. Among the most-prominent electrocatalysts capable of water oxidation at low overpotentials are Ru(bda)L-2-type catalysts. Although many studies were dedicated to the investigation of the influence of structural variations, the true implication of the bda backbone on catalysis remains mostly unclarified. In this work, we further investigated if electronic effects are contributing to catalysis by Ru(bda)(pic)(2) or if the intrinsic catalytic activity mainly originates from the structural features of the ligand. Through introduction of pyrazines in the bda backbone, forming Ru(N-1-bda)(pic)(2) and Ru(N-2-bda)(pic)(2), electronic differences were maximized while minimizing changes in the geometry and other intermolecular interactions. Through a combination of electrochemical analysis, chemical oxygen evolution, and density functional theory calculations, we reveal that the catalytic activity is unaffected by the electronic features of the backbone and that the unique bimolecular reactivity of the Ru(bda)L-2 family of catalysts thus purely depends on the spatial geometry of the ligand.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2021
National Category
Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-296123 (URN)10.1021/acs.inorgchem.0c03339 (DOI)000643574200073 ()33382240 (PubMedID)2-s2.0-85100064913 (Scopus ID)
Note

QC 20210531

Available from: 2021-05-31 Created: 2021-05-31 Last updated: 2022-06-25Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-0672-9965

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