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McCarthy, B. D., Beiler, A. M., Johnson, B. A., Liseev, T., Castner, A. T. & Ott, S. (2020). Analysis of electrocatalytic metal-organic frameworks. Coordination chemistry reviews, 406, Article ID 213137.
Open this publication in new window or tab >>Analysis of electrocatalytic metal-organic frameworks
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2020 (English)In: Coordination chemistry reviews, ISSN 0010-8545, E-ISSN 1873-3840, Vol. 406, article id 213137Article, review/survey (Refereed) Published
Abstract [en]

The electrochemical analysis of molecular catalysts for the conversion of bulk feedstocks into energy-rich clean fuels has seen dramatic advances in the last decade. More recently, increased attention has focused on the characterization of metal-organic frameworks (MOFs) containing well-defined redox and catalytically active sites, with the overall goal to develop structurally stable materials that are industrially relevant for large-scale solar fuel syntheses. Successful electrochemical analysis of such materials draws heavily on well-established homogeneous techniques, yet the nature of solid materials presents additional challenges. In this tutorial-style review, we cover the basics of electrochemical analysis of electroactive MOFs, including considerations of bulk stability, methods of attaching MOFs to electrodes, interpreting fundamental electrochemical data, and finally electrocatalytic kinetic characterization. We conclude with a perspective of some of the prospects and challenges in the field of electrocatalytic MOFs. 

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2020
Keywords
Metal-organic frameworks, Electrochemistry, Electrocatalysis, Electroactive thin films
National Category
Inorganic Chemistry Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-407107 (URN)10.1016/j.ccr.2019.213137 (DOI)000510959500004 ()
Funder
EU, European Research Council, ERC-CoG2015-681895_MOFcatSwedish Energy AgencyStiftelsen Olle Engkvist Byggmästare
Available from: 2020-03-19 Created: 2020-03-19 Last updated: 2020-03-19Bibliographically approved
Johnson, B. A. (2020). Interrogating Diffusional Mass and Charge Transport in Catalytic Metal-Organic Frameworks. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Interrogating Diffusional Mass and Charge Transport in Catalytic Metal-Organic Frameworks
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Molecular catalysts are efficient and selective for the electrochemical conversion of small molecules for energy conversion. Application of molecular species in a large-scale industrial setting requires stabilization in a heterogeneous support material. Metal-organic frameworks (MOFs), having high surface areas for increased active site density, have shown promise as potential platforms in which to incorporate molecular catalysts. However, moving from a homogenous environment to catalysis in porous media, necessitates efficient mass and charge transport to the imbedded catalysts. Either diffusional charge transport or diffusion of substrate have the potential to limit the overall observed rate of product formation, if they are slower than the intrinsic rate of the catalytic reaction. This thesis seeks to examine the effect of diffusional mass and charge transport on molecular catalysis in MOFs.

First, chemically driven water oxidation is examined using a molecular ruthenium catalyst covalently grafted in MIL(Cr)-101 (MIL = Materials Institute Lavoisier) (Chapter 3). A formal kinetic analysis using a steady-state reaction-diffusion model revealed the limitations incurred by mass transport of the chemical oxidant through the pores of the framework. Importantly, it was shown that interference from mass transport obscures turn-over frequencies, and intrinsic reaction kinetics are only measured under certain conditions. The following chapter entails a modified electrode with a UiO MOF film (UiO = University of Oslo)  containing a molecular catalyst, which is used for electrochemically mediated water oxidation (Chapter 4). The diffusional electron-hopping process is examined and discussed in the context of optimizing overall catalytic current densities. In Chapter 5, a new UiO-type MOF thin film is developed containing exclusively molecularly discrete naphthalene diimide linkers, which are redox-active. This can potentially provide charge transport pathways to imbedded catalysts in a two-component system. In addition, the electron-hopping diffusion coefficient was characterized in both non-aqueous and aqueous electrolytes. Lastly, the capacity of the charge-hopping process occurring in these redox-active MOF films to drive a model catalytic reaction is quantified (Chapter 6). Analysis by cyclic voltammetry is utilized to gain insight into the contributions to the current from the catalytic reaction, electron-hopping, substrate diffusion in the film, as well as mass transport in solution. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2020. p. 115
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1895
Keywords
metal-organic frameworks, molecular catalysis, reaction-diffusion, electrochemistry, water oxidation, charge transport
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-402206 (URN)978-91-513-0849-4 (ISBN)
Public defence
2020-02-28, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2020-02-06 Created: 2020-01-13 Last updated: 2020-02-06
Wang, V.-C. C. & Johnson, B. A. (2019). Interpreting the Electrocatalytic Voltammetry of Homogeneous Catalysts by the Foot of the Wave Analysis and Its Wider Implications. ACS Catalysis, 9(8), 7109-7123
Open this publication in new window or tab >>Interpreting the Electrocatalytic Voltammetry of Homogeneous Catalysts by the Foot of the Wave Analysis and Its Wider Implications
2019 (English)In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 9, no 8, p. 7109-7123Article in journal (Refereed) Published
Abstract [en]

Mechanistic studies of electrocatalytic reactions play a crucial role in developing efficient electrocatalysts and solar-fuel devices. The foot of the wave analysis (FOWA) for cyclic voltammetry, recently developed by Saveant and Costentin, provides a powerful means to evaluate the performance of molecular electrocatalysts. However, there is a considerable amount of confusion in the community on how to interpret FOWA in multielectron electrochemical reactions. Herein, we further expand their earlier models from the Nernstian region to all scenarios (i.e., including non-Nernstian behavior) and systematically examine individual parameters, such as formal potentials and reaction rate constants, to explore deeper insights and limitations. Detailed analysis from in silico voltammograms based on different mechanistic models reveals characteristic features of FOWA traces for different kinetic phenomena, which is useful to diagnose kinetic profiles and elucidate the limits of FOWA. The lessons learned from these analyses are further used to reconcile the discrepancy of rate constants determined by FOWA versus other methods, such as time-resolved spectroscopy, for molecular electrocatalysts that catalyze proton reduction or the reduction of CO2 to CO. Such reconciliation demonstrates that electrochemical methods along with FOWA can serve as an alternative tool to determine kinetic information and probe mechanistic insights, which otherwise may be challenging and complicated to achieve by conventional methods. In addition, general guidelines and warnings are also presented to avoid potential errors or mishandling when using FOWA.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
Keywords
electrocatalysis, FOWA, mechanistic studies, hydrogen evolution reaction, CO2 reduction, homogeneous electrocatalysts
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-393746 (URN)10.1021/acscatal.9b00850 (DOI)000480503700052 ()
Available from: 2019-11-11 Created: 2019-11-11 Last updated: 2019-11-11Bibliographically approved
Queyriaux, N., Swords, W. B., Agarwata, H., Johnson, B. A., Ott, S. & Hammarström, L. (2019). Mechanistic insights on the non-innocent role of electron donors: reversible photocapture of CO2 by Ru-II-polypyridyl complexes. Dalton Transactions, 48(45), 16894-16898
Open this publication in new window or tab >>Mechanistic insights on the non-innocent role of electron donors: reversible photocapture of CO2 by Ru-II-polypyridyl complexes
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2019 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 48, no 45, p. 16894-16898Article in journal (Refereed) Published
Abstract [en]

The ability of [Ru-II((t)Butpy)(dmbpy)(MeCN)](2+) (1-MeCN) to capture CO2, with the assistance of triethanolamine (TEOA), has been assessed under photocatalytically-relevant conditions. The photolability of 1-MeCN has proven essential to generate a series of intermediates which only differ by the nature of their monodentate ligand. In DMF, ligand photoexchange of 1-MeCN to give [Ru-II((t)Butpy)(dmbpy)(DMF)](2+) (1-DMF) proceeds smoothly with a quantum yield of 0.011. However, in the presence of TEOA, this process was disrupted, leading to the formation of a mixture of 1-DMF and [Ru-II((t)Butpy)(dmbpy)(TEOA)](+) (1-TEOA). An equilibrium constant of 3 was determined. Interestingly, 1-TEOA demonstrated an ability to reversibly catch and release CO2 making it a potentially crucial intermediate towards CO2 reduction.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2019
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-400006 (URN)10.1039/c9dt03461g (DOI)000498690100006 ()31642825 (PubMedID)
Funder
Swedish Energy Agency, 11674-8Stiftelsen Olle Engkvist Byggmästare, 2016/3NordForsk
Available from: 2019-12-19 Created: 2019-12-19 Last updated: 2019-12-19Bibliographically approved
Johnson, B. A., Bhunia, A., Fei, H., Cohen, S. M. & Ott, S. (2018). Development of a UiO-Type Thin Film Electrocatalysis Platform with Redox-Active Linkers. Journal of the American Chemical Society, 140(8), 2985-2994
Open this publication in new window or tab >>Development of a UiO-Type Thin Film Electrocatalysis Platform with Redox-Active Linkers
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2018 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 140, no 8, p. 2985-2994Article in journal (Refereed) Published
Abstract [en]

Metal–organic frameworks (MOFs) as electrocatalysis scaffolds are appealing due to the large concentration of catalytic units that can be assembled in three dimensions. To harness the full potential of these materials, charge transport to the redox catalysts within the MOF has to be ensured. Herein, we report the first electroactive MOF with the UiO/PIZOF topology (Zr(dcphOH-NDI)), i.e., one of the most widely used MOFs for catalyst incorporation, by using redox-active naphthalene diimide-based linkers (dcphOH-NDI). Hydroxyl groups were included on the dcphOH-NDI linker to facilitate proton transport through the material. Potentiometric titrations of Zr(dcphOH-NDI) show the proton-responsive behavior via the −OH groups on the linkers and the bridging Zr-μ3-OH of the secondary building units with pKa values of 6.10 and 3.45, respectively. When grown directly onto transparent conductive fluorine-doped tin oxide (FTO), 1 μm thin films of Zr(dcphOH-NDI)@FTO could be achieved. Zr(dcphOH-NDI)@FTO displays reversible electrochromic behavior as a result of the sequential one-electron reductions of the redox-active NDI linkers. Importantly, 97% of the NDI sites are electrochemically active at applied potentials. Charge propagation through the thin film proceeds through a linker-to-linker hopping mechanism that is charge-balanced by electrolyte transport, giving rise to cyclic voltammograms of the thin films that show characteristics of a diffusion-controlled process. The equivalent diffusion coefficient, De, that contains contributions from both phenomena was measured directly by UV/vis spectroelectrochemistry. Using KPF6 as electrolyte, De was determined to be De(KPF6) = (5.4 ± 1.1) × 10–11 cm2 s–1, while an increase in countercation size to n-Bu4N+ led to a significant decrease of De by about 1 order of magnitude (De(n-Bu4NPF6) = (4.0 ± 2.5) × 10–12 cm2 s–1).

National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-351270 (URN)10.1021/jacs.7b13077 (DOI)000426617700044 ()29421875 (PubMedID)
Funder
Swedish Research Council
Available from: 2018-06-04 Created: 2018-06-04 Last updated: 2020-01-13Bibliographically approved
Bhunia, A., Johnson, B. A., Czapla-Masztafiak, J., Sá, J. & Ott, S. (2018). Formal water oxidation turnover frequencies from MIL-101(Cr) anchored Ru(bda) depend on oxidant concentration. Chemical Communications, 54, 7770-7773
Open this publication in new window or tab >>Formal water oxidation turnover frequencies from MIL-101(Cr) anchored Ru(bda) depend on oxidant concentration
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2018 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 54, p. 7770-7773Article in journal (Refereed) Published
Abstract [en]

The molecular water oxidation catalyst [Ru(bda)(L)(2)] has been incorporated into pyridine-decorated MIL-101(Cr) metal-organic frameworks. The resulting MIL-101@Ru materials exhibit turnover frequencies (TOFs) up to ten times higher compared to the homogenous reference. An unusual dependence of the formal TOFs on oxidant concentration is observed that ultimately arises from differing amounts of catalysts in the MOF crystals being active.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2018
National Category
Inorganic Chemistry Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-361265 (URN)10.1039/c8cc02300j (DOI)000438237700009 ()29926035 (PubMedID)
Funder
Swedish Research CouncilSwedish Energy AgencyKnut and Alice Wallenberg FoundationEU, European Research Council, ERC-CoG2015-681895_MOFcat
Note

De två första författarna delar förstaförfattarskapet.

Available from: 2018-10-11 Created: 2018-10-11 Last updated: 2020-01-13Bibliographically approved
Johnson, B. A., Bhunia, A. & Ott, S. (2017). Electrocatalytic water oxidation by a molecular catalyst incorporated into a metal-organic framework thin film. Dalton Transactions, 46(5), 1382-1388
Open this publication in new window or tab >>Electrocatalytic water oxidation by a molecular catalyst incorporated into a metal-organic framework thin film
2017 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 46, no 5, p. 1382-1388Article in journal (Refereed) Published
Abstract [en]

A molecular water oxidation catalyst, [Ru(tpy)(dcbpy)(OH2)](ClO4)(2) (tpy = 2,2': 6',2''-terpyridine, dcbpy = 2,2'-bipyridine- 5,5'-dicarboxylic acid) [1], has been incorporated into FTO-grown thin films of UiO-67 (UiO = University of Oslo), by post-synthetic ligand exchange. Cyclic voltammograms (0.1 M borate buffer at pH = 8.4) of the resulting UiO67-[RuOH2]@ FTO show a reversible wave associated with the Ru-III/II couple in the anodic scan, followed by a large current response that arises from electrocatalytic water oxidation beyond 1.1 V vs. Ag/AgCl. Water oxidation can be observed at an applied potential of 1.5 V over the timescale of hours with a current density of 11.5 mu A cm(-2). Oxygen evolution was quantified in situ over the course of the experiment, and the Faradaic efficiency was calculated as 82%. Importantly, the molecular integrity of [1] during electrocatalytic water oxidation is maintained even on the timescale of hours under turnover conditions and applied voltage, as evidenced by the persistence of the wave associated with the Ru-III/II couple in the CV. This experiment highlights the capability of metal organic frameworks like UiO-67 to stabilize the molecular structure of catalysts that are prone to form higher clusters in homogenous phase.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2017
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-319681 (URN)10.1039/c6dt03718frsc.li/dalton (DOI)000395442700005 ()27845800 (PubMedID)
Funder
Swedish Research CouncilSwedish Energy AgencyKnut and Alice Wallenberg Foundation
Available from: 2017-04-07 Created: 2017-04-07 Last updated: 2020-01-13Bibliographically approved
Johnson, B. A., Maji, S., Agarwala, H., White, T. A., Mijangos, E. & Ott, S. (2016). Activating a Low Overpotential CO2 Reduction Mechanism by a Strategic Ligand Modification on a Ruthenium Polypyridyl Catalyst. Angewandte Chemie International Edition, 55(5)
Open this publication in new window or tab >>Activating a Low Overpotential CO2 Reduction Mechanism by a Strategic Ligand Modification on a Ruthenium Polypyridyl Catalyst
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2016 (English)In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 55, no 5Article in journal (Refereed) Published
Abstract [en]

The introduction of a simple methyl substituent on the bipyridine ligand of [Ru(tBu(3)tpy)(bpy)(NCCH3)](2+) (tBu(3)tpy = 4,4',4''-tri-tert-butyl-2,2':6',2''-terpyridine; bpy = 2,2'-bipyridine) gives rise to a highly active electrocatalyst for the reduction of CO2 to CO. The methyl group enables CO2 binding already at the one-electron reduced state of the complex to enter a previously not accessible catalytic cycle that operates at the potential of the first reduction. The complex turns over with a Faradaic efficiency close to unity and at an overpotential that is amongst the lowest ever reported for homogenous CO2 reduction catalysts.

Keywords
carbon dioxide reduction, electrocatalysis, overpotential, reaction mechanisms, ruthenium
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-280898 (URN)10.1002/anie.201508490 (DOI)000369854000042 ()26671836 (PubMedID)
Funder
Swedish Research CouncilSwedish Energy AgencyKnut and Alice Wallenberg FoundationWenner-Gren Foundations
Available from: 2016-03-16 Created: 2016-03-16 Last updated: 2017-11-30Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6570-6392

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