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Huang, J., Xu, B., Tian, L., Pati, P. B., Etman, A. S., Sun, J., . . . Tian, H. (2019). A heavy metal-free CuInS2 quantum dot sensitized NiO photocathode with a Re molecular catalyst for photoelectrochemical CO2 reduction. Chemical Communications, 55(55), 7918-7921
Open this publication in new window or tab >>A heavy metal-free CuInS2 quantum dot sensitized NiO photocathode with a Re molecular catalyst for photoelectrochemical CO2 reduction
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2019 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 55, no 55, p. 7918-7921Article in journal (Refereed) Published
Abstract [en]

Heavy metal-free CuInS2 quantum dots (QDs) were employed as a photosensitizer on a NiO photocathode to drive an immobilized molecular Re catalyst for photoelectrochemical CO2 reduction for the first time. A photocurrent of 25 mu A cm(-2) at -0.87 V vs. NHE was obtained, providing a faradaic efficiency of 32% for CO production.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2019
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-390783 (URN)10.1039/c9cc04222a (DOI)000474306200003 ()31215919 (PubMedID)
Funder
Swedish Energy Agency, 11674-8Göran Gustafsson Foundation for Research in Natural Sciences and MedicineStiftelsen Olle Engkvist Byggmästare
Available from: 2019-08-16 Created: 2019-08-16 Last updated: 2019-08-16Bibliographically approved
Parada, G. A., Goldsmith, Z. K., Kolmar, S., Pettersson-Rimgard, B., Mercado, B. Q., Hammarström, L., . . . Mayer, J. M. (2019). Concerted proton-electron transfer reactions in the Marcus inverted region. Science, 364(6439), 471-475
Open this publication in new window or tab >>Concerted proton-electron transfer reactions in the Marcus inverted region
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2019 (English)In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 364, no 6439, p. 471-475Article in journal (Refereed) Published
Abstract [en]

Electron transfer reactions slow down when they become very thermodynamically favorable, a counterintuitive interplay of kinetics and thermodynamics termed the inverted region in Marcus theory. Here we report inverted region behavior for proton-coupled electron transfer (PCET). Photochemical studies of anthracene-phenol-pyridine triads give rate constants for PCET charge recombination that are slower for the more thermodynamically favorable reactions. Photoexcitation forms an anthracene excited state that undergoes PCET to create a charge-separated state. The rate constants for return charge recombination show an inverted dependence on the driving force upon changing pyridine substituents and the solvent. Calculations using vibronically nonadiabatic PCET theory yield rate constants for simultaneous tunneling of the electron and proton that account for the results.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-383503 (URN)10.1126/science.aaw4675 (DOI)000466809600031 ()30975771 (PubMedID)
Funder
Swedish Research Council, 2016-04271
Available from: 2019-05-17 Created: 2019-05-17 Last updated: 2019-05-17Bibliographically approved
Aster, A., Wang, S., Mirmohades, M., Esmieu, C., Berggren, G., Hammarström, L. & Lomoth, R. (2019). Metal vs. ligand protonation and the alleged proton-shuttling role of the azadithiolate ligand in catalytic H-2 formation with FeFe hydrogenase model complexes. Chemical Science, 10(21), 5582-5588
Open this publication in new window or tab >>Metal vs. ligand protonation and the alleged proton-shuttling role of the azadithiolate ligand in catalytic H-2 formation with FeFe hydrogenase model complexes
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2019 (English)In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 10, no 21, p. 5582-5588Article in journal (Refereed) Published
Abstract [en]

Electron and proton transfer reactions of diiron complexes [Fe(2)adt(CO)(6)] (1) and [Fe(2)adt(CO)(4)(PMe3)(2)] (4), with the biomimetic azadithiolate (adt) bridging ligand, have been investigated by real-time IR- and UV-vis-spectroscopic observation to elucidate the role of the adt-N as a potential proton shuttle in catalytic H-2 formation. Protonation of the one-electron reduced complex, 1(-), occurs on the adt-N yielding 1H and the same species is obtained by one-electron reduction of 1H(+). The preference for ligand vs. metal protonation in the Fe-2(i,0) state is presumably kinetic but no evidence for tautomerization of 1H to the hydride 1Hy was observed. This shows that the adt ligand does not work as a proton relay in the formation of hydride intermediates in the reduced catalyst. A hydride intermediate 1HHy(+) is formed only by protonation of 1H with stronger acid. Adt protonation results in reduction of the catalyst at much less negative potential, but subsequent protonation of the metal centers is not slowed down, as would be expected according to the decrease in basicity. Thus, the adtH(+) complex retains a high turnover frequency at the lowered overpotential. Instead of proton shuttling, we propose that this gain in catalytic performance compared to the propyldithiolate analogue might be rationalized in terms of lower reorganization energy for hydride formation with bulk acid upon adt protonation.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2019
National Category
Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-390686 (URN)10.1039/c9sc00876d (DOI)000474412700015 ()31293742 (PubMedID)
Funder
Swedish Research Council, 621-2014-5670Swedish Research Council, 2016-04271Swedish Research Council Formas, 213-2014-880
Available from: 2019-08-16 Created: 2019-08-16 Last updated: 2019-08-16Bibliographically approved
Liu, T., Guo, M., Orthaber, A., Lomoth, R., Lundberg, M., Ott, S. & Hammarström, L. (2018). Accelerating proton-coupled electron transfer of metal hydrides in catalyst model reactions. Nature Chemistry, 10(8), 881-887
Open this publication in new window or tab >>Accelerating proton-coupled electron transfer of metal hydrides in catalyst model reactions
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2018 (English)In: Nature Chemistry, ISSN 1755-4330, E-ISSN 1755-4349, Vol. 10, no 8, p. 881-887Article in journal (Refereed) Published
Abstract [en]

Metal hydrides are key intermediates in catalytic proton reduction and dihydrogen oxidation. There is currently much interest in appending proton relays near the metal centre to accelerate catalysis by proton-coupled electron transfer (PCET). However, the elementary PCET steps and the role of the proton relays are still poorly understood, and direct kinetic studies of these processes are scarce. Here, we report a series of tungsten hydride complexes as proxy catalysts, with covalently attached pyridyl groups as proton acceptors. The rate of their PCET reaction with external oxidants is increased by several orders of magnitude compared to that of the analogous systems with external pyridine on account of facilitated proton transfer. Moreover, the mechanism of the PCET reaction is altered by the appended bases. A unique feature is that the reaction can be tuned to follow three distinct PCET mechanisms-electron-first, proton-first or a concerted reaction-with very different sensitivities to oxidant and base strength. Such knowledge is crucial for rational improvements of solar fuel catalysts.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-357209 (URN)10.1038/s41557-018-0076-x (DOI)000439420400015 ()30013192 (PubMedID)
Funder
Swedish Research Council, 2016-04271Knut and Alice Wallenberg Foundation, 2011.0067
Available from: 2018-08-13 Created: 2018-08-13 Last updated: 2019-01-04Bibliographically approved
Hammarström, L., Abdellah, M. & Gilbert Gatty, M. (2018). Capturing intermediates of molecular catalyst/semiconductor systems by transient mid-IR spectroscopy.. Paper presented at 255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water, MAR 18-22, 2018, New Orleans, USA.. Abstract of Papers of the American Chemical Society, 255
Open this publication in new window or tab >>Capturing intermediates of molecular catalyst/semiconductor systems by transient mid-IR spectroscopy.
2018 (English)In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 255Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
Washington, D.C.: American Chemical Society (ACS), 2018
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-368926 (URN)000435539902256 ()
Conference
255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water, MAR 18-22, 2018, New Orleans, USA.
Note

Meeting Abstract: 109

Available from: 2018-12-11 Created: 2018-12-11 Last updated: 2018-12-11Bibliographically approved
Huang, J., Gilbert Gatty, M., Xu, B., Pati, P. B., Etman, A. S., Tian, L., . . . Tian, H. (2018). Covalently linking CuInS2 quantum dots with a Re catalyst by click reaction for photocatalytic CO2 reduction. Dalton Transactions, 47(31), 10775-10783
Open this publication in new window or tab >>Covalently linking CuInS2 quantum dots with a Re catalyst by click reaction for photocatalytic CO2 reduction
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2018 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 47, no 31, p. 10775-10783Article in journal (Refereed) Published
Abstract [en]

Covalently linking photosensitizers and catalysts in an inorganic-organic hybrid photocatalytic system is beneficial for efficient electron transfer between these components. However, general and straightforward methods to covalently attach molecular catalysts on the surface of inorganic semiconductors are rare. In this work, a classic rhenium bipyridine complex (Re catalyst) has been successfully covalently linked to the low toxicity CuInS2 quantum dots (QDs) by click reaction for photocatalytic CO2 reduction. Covalent bonding between the CuInS2 QDs and the Re catalyst in the QD-Re hybrid system is confirmed by UV-visible absorption spectroscopy, Fourier-transform infrared spectroscopy and energy-dispersive X-ray measurements. Time-correlated single photon counting and ultrafast time-resolved infrared spectroscopy provide evidence for rapid photo-induced electron transfer from the QDs to the Re catalyst. Upon photo-excitation of the QDs, the singly reduced Re catalyst is formed within 300 fs. Notably, the amount of reduced Re in the linked hybrid system is more than that in a sample where the QDs and the Re catalyst are simply mixed, suggesting that the covalent linkage between the CuInS2 QDs and the Re catalyst indeed facilitates electron transfer from the QDs to the Re catalyst. Such an ultrafast electron transfer in the covalently linked CuInS2 QD-Re hybrid system leads to enhanced photocatalytic activity for CO2 reduction, as compared to the conventional mixture of the QDs and the Re catalyst.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-363108 (URN)10.1039/c8dt01631c (DOI)000441151700051 ()30019727 (PubMedID)
Funder
Swedish Research CouncilSwedish Energy AgencyGöran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of TechnologyStiftelsen Olle Engkvist Byggmästare
Available from: 2018-10-15 Created: 2018-10-15 Last updated: 2018-10-15Bibliographically approved
Gilbert Gatty, M., Pullen, S., Sheibani, E., Tian, H., Ott, S. & Hammarström, L. (2018). Direct evidence of catalyst reduction on dye and catalyst co-sensitized NiO photocathodes by mid-infrared transient absorption spectroscopy. Chemical Science, 9(22), 4983-4991
Open this publication in new window or tab >>Direct evidence of catalyst reduction on dye and catalyst co-sensitized NiO photocathodes by mid-infrared transient absorption spectroscopy
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2018 (English)In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 9, no 22, p. 4983-4991Article in journal (Refereed) Published
Abstract [en]

Co-sensitization of molecular dyes and catalysts on semiconductor surfaces is a promising strategy to build photoelectrodes for solar fuel production. In such a photoelectrode, understanding the charge transfer reactions between the molecular dye, catalyst and semiconductor material is key to guide further improvement of their photocatalytic performance. Herein, femtosecond mid-infrared transient absorption spectroscopy is used, for the first time, to probe charge transfer reactions leading to catalyst reduction on co-sensitized nickel oxide (NiO) photocathodes. The NiO films were co-sensitized with a molecular dye and a proton reducing catalyst from the family of [FeFe](bdt)(CO)(6) (bdt = benzene-1,2-dithiolate) complexes. Two dyes were used: an organic push-pull dye denoted E2 with a triarylamine-oligothiophene-dicyanovinyl structure and a coumarin 343 dye. Upon photo-excitation of the dye, a clear spectroscopic signature of the reduced catalyst is observed a few picoseconds after excitation in all co-sensitized NiO films. However, kinetic analysis of the transient absorption signals of the dye and reduced catalyst reveal important mechanistic differences in the first reduction of the catalyst depending on the co-sensitized molecular dye (E2 or C343). While catalyst reduction is preceded by hole injection in NiO in C343-sensitized NiO films, the singly reduced catalyst is formed by direct electron transfer from the excited dye E2* to the catalyst in E2-sensitized NiO films. This change in mechanism also impacts the lifetime of the reduced catalyst, which is only ca. 50 ps in E2-sensitized NiO films but is >5 ns in C343-sensitized NiO films. Finally, the implication of this mechanistic study for the development of better co-sensitized photocathodes is discussed.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-358380 (URN)10.1039/c8sc00990b (DOI)000434693300008 ()
Funder
Swedish Energy Agency, 11645-5
Available from: 2018-08-29 Created: 2018-08-29 Last updated: 2018-08-29Bibliographically approved
Tang, Y., Cao, X., Honarfar, A., Abdellah, M., Chen, C., Avila, J., . . . Chi, Q. (2018). Inorganic Ions Assisted the Anisotropic Growth of CsPbCl3 Nanowires with Surface Passivation Effect. ACS Applied Materials and Interfaces, 10(35), 29574-29582
Open this publication in new window or tab >>Inorganic Ions Assisted the Anisotropic Growth of CsPbCl3 Nanowires with Surface Passivation Effect
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2018 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 35, p. 29574-29582Article in journal (Refereed) Published
Abstract [en]

All-inorganic halide perovskite nanowires (NWs) exhibit improved thermal and hydrolysis stability and could thus play a vital role in nanoscale optoelectronics. Among them, blue-light-based devices are extremely limited because of the lack of a facile method to obtain high-purity CsPbCl3 NWs. Herein, we report a direct and facile method for the synthesis of CsPbCl3 NWs assisted by inorganic ions that served both as a morphology controlling agent for the anisotropic growth of nanomaterials and a surface passivation species modulating the surface of nanomaterials. This new approach allows us to obtain high-purity and size-uniform NWs as long as 500 nm in length and 20 nm in diameter with high reproducibility. X-ray photoelectron spectroscopy and ultrafast spectroscopic measurements confirmed that a reduced band gap caused by the surface species of NWs relative to nanocubes (NCs) was achieved at the photon energy of 160 eV because of the hybrid surface passivation contributed by adsorbed inorganic ions. The resulting NWs demonstrate significantly enhanced photoelectrochemical performances, 3.5-fold increase in the photocurrent generation, and notably improved stability compared to their NC counterparts. Our results suggest that the newly designed NWs could be a promising material for the development of nanoscale optoelectronic devices.

Keywords
inorganic halide perovskite, CsPbCl3 nanowires, surface passivation, photoelectrochemical cell, electron and hole injection, ultrafast spectroscopy
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-365656 (URN)10.1021/acsami.8b09113 (DOI)000444355700038 ()30088920 (PubMedID)
Funder
Swedish Research Council, 2017-05337
Available from: 2018-11-16 Created: 2018-11-16 Last updated: 2018-11-16Bibliographically approved
Tyburski, R., Föhlinger, J. & Hammarström, L. (2018). Light Driven Electron Transfer in Methylbipyridine/Phenol Complexes Is Not Proton Coupled. Paper presented at 18th Meeting on Time-Resolved Vibrational Spectroscopy (TRVS), 2017, Cambridge, ENGLAND. Journal of Physical Chemistry A, 122(18), 4425-4429
Open this publication in new window or tab >>Light Driven Electron Transfer in Methylbipyridine/Phenol Complexes Is Not Proton Coupled
2018 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 122, no 18, p. 4425-4429Article in journal (Refereed) Published
Abstract [en]

The pursuit of systems that undergo optical electron proton transfer (photo-EPT) is very attractive, due to the wealth of information contained in the absorption spectra of such complexes. However, separating photo-EPT transitions from conventional charge transfer states remains a major challenge. In this study, we show that optical charge transfer in a complex between 4-methoxyphenol and N-methyl-4,4'-bipyridyl, previously assigned to occur through photo-EPT involving a hydrogen bond between the reactants (GagliardiC. J.; WangL.; DongareP.; BrennamanM. K.; PapanikolasJ. M.; MeyerT. J.; ThompsonD. W. Proc. Natl. Acad. Sci. U.S.A. 2016, 113, 11106-11109), does not lead to protonation of the acceptor molecule. Additionally, we propose that association of the complex is likely due to donor-acceptor interactions rather than hydrogen bonding.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-356453 (URN)10.1021/acs.jpca.8b02221 (DOI)000432204200005 ()29641888 (PubMedID)
Conference
18th Meeting on Time-Resolved Vibrational Spectroscopy (TRVS), 2017, Cambridge, ENGLAND
Funder
Swedish Research Council, 2016-04271
Available from: 2018-08-02 Created: 2018-08-02 Last updated: 2018-08-13Bibliographically approved
Parada, G., Kolmar, S., Pettersson-Rimgard, B., Hammarström, L. & Mayer, J. (2018). Marcus inverted region in photo-induced proton coupled electron transfer. Paper presented at 255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water, MAR 18-22, 2018, New Orleans, LA. Abstract of Papers of the American Chemical Society, 255
Open this publication in new window or tab >>Marcus inverted region in photo-induced proton coupled electron transfer
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2018 (English)In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 255Article in journal, Meeting abstract (Other academic) Published
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-367234 (URN)000435539902425 ()
Conference
255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water, MAR 18-22, 2018, New Orleans, LA
Available from: 2018-12-06 Created: 2018-12-06 Last updated: 2018-12-06Bibliographically approved
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