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Publication highlights

Picks of our best science this year

June 11 2019:  Jing Huang, Bo Xu, Lei Tian, Palas Baran Pati, Ahmed S. Etman, Junliang Sun, Leif Hammarström and Haining Tian published an article in Chemical Communications: 

A heavy metal-free CuInS2 quantum dot sensitized NiO photocathode with a Re molecular catalyst for photoelectrochemical CO2 reduction.

Abstract: 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 μA cm−2 at −0.87 V vs. NHE was obtained, providing a faradaic efficiency of 32% for CO production.

May 2 2019:  Alexander Aster, Shihuai Wang, Mohammad Mirmohades, Charlène Esmieu, Gustav BerggrenLeif Hammarström and Reiner Lomoth published an article in Chemical Science: 

Metal vs. ligand protonation and the alleged proton-shuttling role of the azadithiolate ligand in catalytic H2 formation with FeFe hydrogenase model complexes.

Abstract: Electron and proton transfer reactions of diiron complexes [Fe2adt(CO)6] (1) and [Fe2adt(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 H2 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 Fe2(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.

April 11 2019:  Giovanny A. Parada, Zachary K. Goldsmith, Scott Kolmar, Belinda Pettersson Rimgard, Brandon Q. Mercado, Leif Hammarström, Sharon Hammes-Schiffer, and James M. Mayer published an article in Science: 

Concerted proton-electron transfer reactions in the Marcus inverted region.

Abstract: Electron transfer (ET) reactions slow down when they become thermodynamically very 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). Specifically, 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.

February 21 2019:  Sonja Pullen, Somnath Maji, Matthias Stein and Sascha Ott published an article in Dalton transactions: 

Restricted rotation of an Fe(CO)2(PL3)-subunit in [FeFe]-hydrogenase active site mimics by intramolecular ligation.

Abstract: A new series of homodinuclear iron complexes as models of the [FeFe]-hydrogenase active site was prepared and characterized. The complexes of the general formula [Fe2(mcbdt)(CO)5PPh2R] (mcbdt = benzene-1,2-dithiol-3-carboxylic acid) feature covalent tethers that link the mcbdt ligand with the phosphine ligands which are terminally coordinated to one of the Fe centres. The synthetic feasability of the concept is demonstrated with the preparation of three novel complexes. A detailed theoretical investigation showes that by introducing a rigid covalent link between the phosphine and the bridging dithiolate ligands, the rotation of the Fe(CO)2P unit is hindered and higher rotation barriers were calculated compared to nonlinked reference complexes. The concept of restricting Fe(L)3 rotation is an approach to kinetically stabilize terminal hydrides which are reactive intermediates in catalytic proton reduction cycles of the enzymes.

February 18 2019:  Sergii I. Shylin, Mariia V. Pavliuk, Luca D’Amario, Fikret Mamedov, Jacinto Sá, Gustav Berggren and Igor O. Fritsky published an article in Chemical communications: 

Efficient visible light-driven water oxidation catalysed by an iron(IV) clathrochelate complex.

Abstract: A water-stable Fe(IV) clathrochelate complex catalyses fast and homogeneous photochemical oxidation of water to dioxygen with a turnover frequency of 2.27 /s and a maximum turnover number of 365. An Fe(V) intermediate generated under catalytic conditions is trapped and characterised using EPR and Mössbauer spectroscopy.

January 4 2019:  Kamonchanock Eungrasamee, Rui Miao, Aran Incharoensakdi, Peter Lindblad and Saowarath Jantaro published an article in Biotechnology for biofuels: 

Improved lipid production via fatty acid biosynthesis and free fatty acid recycling in engineered Synechocystis sp. PCC 6803.

Abstract: Cyanobacteria are potential sources for third generation biofuels. Their capacity for biofuel production has been widely improved using metabolically engineered strains. In this study, we employed metabolic engineering design with target genes involved in selected processes including the fatty acid synthesis (a cassette of accD, accA, accC and accB encoding acetyl-CoA carboxylase, ACC), phospholipid hydrolysis (lipA encoding lipase A), alkane synthesis (aar encoding acyl-ACP reductase, AAR), and recycling of free fatty acid (FFA) (aas encoding acyl–acyl carrier protein synthetase, AAS) in the unicellular cyanobacterium Synechocystis sp. PCC 6803.

January 3 2019:  Brigitta Németh, Charlène Esmieu,  Holly J. Redman and Gustav Berggren published an article in Dalton transactions: 

Monitoring H-cluster assembly using a semisynthetic HydF protein.

Abstract: The [FeFe] hydrogenase enzyme interconverts protons and molecular hydrogen with remarkable efficiency. The reaction is catalysed by a unique metallo-cofactor denoted as the H-cluster containing an organometallic dinuclear Fe component, the [2Fe] subsite. The HydF protein delivers a precursor of the [2Fe] subsite to the apo-[FeFe] hydrogenase, thus completing the H-cluster and activating the enzyme. Herein we generate a semi-synthetic form of HydF by loading it with a synthetic low valent dinuclear Fe complex. We show that this semi-synthetic protein is practically indistinguishable from the native protein, and utilize this form of HydF to explore the mechanism of H-cluster assembly. More specifically, we show that transfer of the precatalyst from HydF to the hydrogenase enzyme results in the release of CO, underscoring that the pre-catalyst is a four CO species when bound to HydF. Moreover, we propose that an electron transfer reaction occurs during H-cluster assembly, resulting in an oxidation of the [2Fe] subsite with concomitant reduction of the [4Fe4S] cluster present on the HydF protein. 

January 2019:  Bo Xu, Lei Tian, Ahmed S.Etman, Junliang Sun, and Haining Tian published an article in Nano energy:

Solution-processed nanoporous NiO-dye-ZnO photocathodes: Toward efficient and stable solid-state p-type dye-sensitized solar cells and dye-sensitized photoelectrosynthesis cells.

Abstract: A solution-processed NiO-dye-ZnO photocathode was developed for applications in both solid-state p-type dye-sensitized solar cells (p-ssDSCs) and p-type dye-sensitized photoelectrosynthesis cells (p-DSPECs). In p-ssDSCs, the solar cell using ZnO as electron transport material showed a short circuit current, up to 680 µA cm−2, which is 60-fold larger than that previously reported device using TiO2 as electron transport material with similar architecture. In the p-DSPECs, a remarkable photocurrent of 100 μA cm−2 was achieved in a pH = 5.0 acetate buffer solution under a bias potential at 0.05 V vs RHE with platinum as the proton reduction catalyst. A Faradaic efficiency approaching 100% for the H2 evolution reaction was obtained after photoelectrolysis for 9 h. Importantly, the solution-processed NiO-dye-ZnO photocathode exhibited excellent long-term stability in both p-ssDSCs and p-DSPECs. To the best of our knowledge, this is the first study where a solution-processable, nanoporous NiO-dye-ZnO photocathode is used for both p-ssDSCs and p-DSPECs having both excellent device performance and stability.

 Some of our best science published in 2018!

November 30, 2018: Kasper Skov Kjær, Nidhi Kaul, Om Prakash, Pavel Chábera, Nils W. Rosemann, Alireza Honarfar, Olga Gordivska, Lisa A. Fredin, Karl-Erik Bergquist, Lennart Häggström, Tore Ericsson, Linnea Lindh, Arkady Yartsev, Stenbjörn StyringPing Huang, Jens Uhlig, Jesper Bendix, Daniel Strand, Villy Sundström, Petter Persson, Reiner Lomoth, and Kenneth Wärnmark published an article in Science:

Luminescence and reactivity of a charge-transfer excited iron complex with nanosecond lifetime.

Abstract: Iron’s abundance and rich coordination chemistry are potentially appealing features for photochemical applications. However, the photoexcitable charge-transfer (CT) states of most Fe complexes are limited by picosecond or sub-picosecond deactivation through low-lying metal centered (MC) states, resulting in inefficient electron transfer reactivity and complete lack of photoluminescence. Here we show that octahedral coordination of Fe(III) by two mono-anionic facial tris-carbene ligands can suppress such deactivation dramatically. 

The resulting complex [Fe(phtmeimb)2]+, where phtmeimb is [phenyl(tris(3-methylimidazol-1-ylidene))borate]-, exhibits strong, visible, room temperature photoluminescence with a 2.0 ns lifetime and 2% quantum yield via spin-allowed transition from a ligand-to-metal charge-transfer (2LMCT) state to the ground state (2GS). Reductive and oxidative electron transfer reactions were observed for the 2LMCT state of [Fe(phtmeimb)2]+ in bimolecular quenching studies with methylviologen and diphenylamine.

Fig. 2Electrochemistry and spectroscopy of [Fe(phtmeimb)2]+ in dry acetonitrile at room temperature.

(A) Cyclic and differential pulse voltammetry. (B) Optical absorption (left black curve), normalized photoluminescence (right black) and normalized excitation spectra (red circles). (C) Visible orange photoluminescence of 50 μM [Fe(phtmeimb)2]+ in acetonitrile upon 532 nm excitation.

November 18, 2018:  Ulrike Fluch, Brian D. McCarthy, and Sascha Ott published an article in Dalton transactions:

Post synthetic exchange enables orthogonal click chemistry in a metal organic framework.


Biphenyl-4,4′-dicarboxylic acid derivatives containing either azide or acetylene functional groups were inserted into UiO-67 metal organic frameworks (MOFs) via post synthetic linker exchange. Sequential and orthogonal click reactions could be performed on these modified MOFs by incubating the crystals with small molecule substrates bearing azide or acetylene groups in the presence of a copper catalyst. 1H NMR of digested MOF samples showed that up to 50% of the incorporated linkers could be converted to their “clicked” triazole products. Powder X-ray diffraction confirmed that the UiO-67 structure was maintained throughout all transformations. The click reaction efficiency is discussed in context of MOF crystallite size and pore size. As the incorporation of clicked linkers could be controlled by post synthetic exchange, this work introduces a powerful method of quickly introducing orthogonal modifications into known MOF architectures.

November 15, 2018:  Johannes Messinger, Casper de Lichtenberg, Mun Hon Cheah, Dmitry Shevela, and others published an article in Nature:

Structures of the intermediates of Kok’s photosynthetic water oxidation clock.

Authors: Jan Kern, Ruchira Chatterjee, Iris D. Young, Franklin D. Fuller, Louise Lassalle, Mohamed Ibrahim, Sheraz Gul, Thomas Fransson, Aaron S. Brewster, Roberto Alonso-Mori, Rana Hussein, Miao Zhang, Lacey Douthit, Casper de Lichtenberg, Mun Hon Cheah, Dmitry Shevela, Julia Wersig, Ina Seuffert, Dimosthenis Sokaras, Ernest Pastor, Clemens Weninger, Thomas Kroll, Raymond G. Sierra, Pierre Aller, Agata Butryn, Allen M. Orville, Mengning Liang, Alexander Batyuk, Jason E. Koglin, Sergio Carbajo, Sébastien Boutet, Nigel W. Moriarty, James M. Holton, Holger Dobbek, Paul D. Adams, Uwe Bergmann, Nicholas K. Sauter, Athina Zouni, Johannes Messinger, Junko Yano & Vittal K. Yachandra


Inspired by the period-four oscillation in flash-induced oxygen evolution of photosystem II discovered by Joliot in 1969, Kok performed additional experiments and proposed a five-state kinetic model for photosynthetic oxygen evolution, known as Kok’s S-state clock or cycle. The model comprises four (meta)stable intermediates (S0, S1, S2 and S3) and one transient S4 state, which precedes dioxygen formation occurring in a concerted reaction from two water-derived oxygens bound at an oxo-bridged tetra manganese calcium (Mn4CaO5) cluster in the oxygen-evolving complex. This reaction is coupled to the two-step reduction and protonation of the mobile plastoquinone QB at the acceptor side of PSII. Here, using serial femtosecond X-ray crystallography and simultaneous X-ray emission spectroscopy with multi-flash visible laser excitation at room temperature, we visualize all (meta)stable states of Kok’s cycle as high-resolution structures (2.04–2.08 Å). In addition, we report structures of two transient states at 150 and 400 µs, revealing notable structural changes including the binding of one additional ‘water’, Ox, during the S2→S3 state transition. 

Our results suggest that one water ligand to calcium (W3) is directly involved in substrate delivery. The binding of the additional oxygen Ox in the S3 state between Ca and Mn1 supports O–O bond formation mechanisms involving O5 as one substrate, where Ox is either the other substrate oxygen or is perfectly positioned to refill the O5 position during O2 release. Thus, our results exclude peroxo-bond formation in the S3 state, and the nucleophilic attack of W3 onto W2 is unlikely.

September 27: Rui Miao, Hao Xie and Peter Lindblad published an article in Biotechnology for biofuels:

"Enhancement of photosynthetic isobutanol production in engineered cells of Synechocystis PCC 6803."


Growth, isobutanol/3M1B in-flask and cumulative titer observed in a long-term cultivation experiment. The OD750 was measured every day and product titer was measured every second day. S1, S2, and S3 represent different periods in the steady-state phase.

Cyanobacteria, oxygenic photoautotrophic prokaryotes, can be engineered to produce various valuable chemicals from solar energy and CO2 in direct processes. The concept of photosynthetic production of isobutanol, a promising chemical and drop-in biofuel, has so far been demonstrated for Synechocystis PCC 6803 and Synechococcus elongatus PCC 7942. In Synechocystis PCC 6803, a heterologous expression of α-ketoisovalerate decarboxylase (Kivd) from Lactococcus lactis resulted in an isobutanol and 3-methyl-1-butanol producing strain. Kivd was identified as a bottleneck in the metabolic pathway and its activity was further improved by reducing the size of its substratebinding pocket with a single replacement of serine-286 to threonine. However, isobutanol production still remained low.In the present study, we report on how cultivation conditions significantly affect the isobutanol productionin Synechocystis PCC 6803. A HCl-titrated culture grown under medium light showed the highest isobutanol production with an in-flask titer of 194 mg/L after 10 days, and 435 mg/L at day 40. This corresponds to a cumulative isobutanol production of 911 mg/L, with a maximal production rate of 43.6 mg/L day. The present study demonstrates the importance of a suitable cultivation condition to enhance isobutanol production in Synechocystis PCC 6803. Chemostat should be used to further increase both the total titer as well as the rate of production. Furthermore, identified bottleneck, Kivd, should be expressed at the highest level to further enhance isobutanol production.

September 25: Adam Wegelius,  Namita Khanna,  Charlène Esmieu,  Giovanni Davide Barone,  Filipe Pinto,  Paula Tamagnini,  Gustav Berggren and Peter Lindblad published an article in Energy & Environmental Science:

Generation of a functional, semisynthetic [Fe-Fe]-hydrogenase in a photosynthetic microorganism.


[FeFe]-Hydrogenases are hydrogen producing metalloenzymes with excellent catalytic capacities, highly relevant in the context of a future hydrogen economy. Here we demonstrate the synthetic activation of a heterologously expressed [FeFe]-hydrogenase in living cells of Synechocystis PCC 6803, a photoautotrophic microbial chassis with high potential for biotechnological energy applications. H2-Evolution assays clearly show that the non-native, semi-synthetic enzyme links to the native metabolism in living cells.

August 13: Belinda Pettersson Rimgard, Jens Föhlinger, Jonas Petersson, Marcus Lundberg, Burkhard Zietz, Ann Marie Woys, Stephen A. Miller, Michael R. Wasielewski and Leif Hammarström  published an article in Chemical Science:

Ultrafast interligand electron transfer in cis-[Ru(4,4′-dicarboxylate-2,2′-bipyridine)2(NCS)2]4− and implications for electron injection limitations in dye sensitized solar cells.

Abstract: Interligand electron transfer (ILET) of the lowest metal-to-ligand charge transfer (MLCT) state of N712 (cis-[Ru(dcb)2(NCS)2]4−, where dcb = 4,4′-dicarboxylate-2,2′-bipyridine) in a deuterated acetonitrile solution has been studied by means of femtosecond transient absorption anisotropy in the mid-IR. Time-independent B3LYP density functional calculations were performed to assign vibrational bands and determine their respective transition dipole moments. 

The transient absorption spectral band at 1327 cm−1, assigned to a symmetric carboxylate stretch, showed significant anisotropy. A rapid anisotropy increase (τ1 ≈ 2 ps) was tentatively assigned to vibrational and solvent relaxation, considering the excess energy available after the excited singlet–triplet conversion. Thereafter, the anisotropy decayed to zero with a time constant τ2 ≈ 240 ps, which was assigned to the rotational correlation time of the complex in deuterated acetonitrile. No other distinctive changes to the anisotropy were observed and the amplitude of the slow component at time zero agrees well with that predicted for a random mixture of MLCT localization on either of the two dcb ligands. The results therefore suggest that MLCT randomization over the two dcb ligands occurs on the sub-ps time scale. This is much faster than proposed by previous reports on the related N3 complex [Benkö et al., J. Phys. Chem. B, 2004, 108, 2862, and Waterland et al., J. Phys. Chem. A, 2001, 105, 4019], but in agreement with that found by Wallin and co-workers [J. Phys. Chem. A, 2005, 109, 4697] for the [Ru(bpy)3]2+ (bpy = 2,2′-bipyridine) complex. This suggests that electron injection from the excited dye into TiO2 in dye-sensitized solar cells is not limited by ILET.

July 16: Tianfei Liu, Meiyuan Guo, Andreas Orthaber, Reiner Lomoth, Marcus Lundberg, Sascha Ott  and  Leif Hammarström  published an article in Nature Chemistry:

Accelerating proton-coupled electron transfer of metal hydrides in catalyst model reactions.

Abstract: 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.


June 28: Wai Ling Kwong, Cheng Choo Lee, Andrey Shchukarev, Erik Björn and Johannes Messinger published an article in Journal of Catalysis:

High-performance iron (III) oxide electrocatalyst for water oxidation in strongly acidic media. 


Stable and efficient oxygen evolution reaction (OER) catalysts for the oxidation of water to dioxygen in highly acidic media are currently limited to expensive noble metal (Ir and Ru) oxides since presently known OER catalysts made of inexpensive earth-abundant materials generally suffer anodic corrosion at low pH. In this study, we report that a mixed-polymorph film comprising maghemite and hematite, prepared using spray pyrolysis deposition followed by low-temperature annealing, showed a sustained OER rate (>24 h) corresponding to a current density of 10 mA cm−2 at an initial overpotential of 650 mV, with a Tafel slope of only 56 mV dec−1 and near-100% Faradaic efficiency in 0.5 M H2SO4 (pH 0.3). This performance is remarkable, since iron (III) oxide films comprising only maghemite were found to exhibit a comparable intrinsic activity, but considerably lower stability for OER, while films of pure hematite were OER-inactive. These results are explained by the differences in the polymorph crystal structures, which cause different electrical conductivity and surface interactions with water molecules and protons. Our findings not only reveal the potential of iron (III) oxide as acid-stable OER catalyst, but also highlight the important yet hitherto largely unexplored effect of crystal polymorphism on electrocatalytic OER performance.

June 14: Melina Gilbert Gatty,  Sonja Pullen,  Esmaeil Sheibani,  Haining Tian,  Sascha Ott and  Leif Hammarström  published an article in Chemical Science:

Direct evidence of catalyst reduction on dye and catalyst co-sensitized NiO photocathodes by mid-infrared transient absorption spectroscopy. 

Abstract: 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.

April 17: Alagappan Annamalai, Robin Sandström, Eduardo Gracia-Espino, Nicolas Boulanger, Jean-François Boily, Inge Mühlbacher, Andrey Shchukarev and Thomas Wågberg published an article in ACS Applied Materials and Interfaces:

Influence of Sb5+ as a Double Donor on Hematite (Fe3+) Photoanodes for Surface-Enhanced Photoelectrochemical Water Oxidation. 

Abstract: To exploit the full potential of hematite (α-Fe2O3) as an efficient photoanode for water oxidation, the redox processes occurring at the Fe2O3/electrolyte interface need to be studied in greater detail. Ex situ doping is an excellent technique to introduce dopants onto the photoanode surface and to modify the photoanode/electrolyte interface. In this context, we selected antimony (Sb5+) as the ex situ dopant because it is an effective electron donor and reduces recombination effects and concurrently utilize the possibility to tuning the surface charge and wettability. In the presence of Sb5+ states in Sb-doped Fe2O3 photoanodes, as confirmed by X-ray photoelectron spectroscopy, we observed a 10-fold increase in carrier concentration (1.1 × 1020 vs 1.3 × 1019 cm–3) and decreased photoanode/electrolyte charge transfer resistance (∼990 vs ∼3700 Ω). Furthermore, a broad range of surface characterization techniques such as Fourier-transform infrared spectroscopy, ζ-potential, and contact angle measurements reveal that changes in the surface hydroxyl groups following the ex situ doping also have an effect on the water splitting capability. Theoretical calculations suggest that Sb5+ can activate multiple Fe3+ ions simultaneously, in addition to increasing the surface charge and enhancing the electron/hole transport properties. To a greater extent, the Sb5+- surface-doped determines the interfacial properties of electrochemical charge transfer, leading to an efficient water oxidation mechanism.

April 7: Roghayeh Imani, Zhen Qiu, Reza Younesi, Meysam Pazoki, Daniel L.A.Fernandes, Pavlin D.Mitev, Tomas Edvinsson, and Haining Tian published an article in Nano Energy:

"Unravelling in-situ formation of highly active mixed metal oxide CuInO2 nanoparticles during CO2 electroreduction."


Technologies and catalysts for converting carbon dioxide (CO2) to immobile products are of high interest to minimize greenhouse effects. Copper(I) is a promising catalytic active state of copper but hampered by the inherent instability in comparison to copper(II) or copper(0). Here, we report a stabilization of the catalytic active state of copper(I) by the formation of a mixed metal oxide CuInO2 nanoparticle during the CO2 electroreduction. Our result shows the incorporation of nanoporous Sn:In2O3 interlayer to Cu2O pre-catalyst system lead to the formation of CuInO2 nanoparticles with remarkably higher activity for CO2 electroreduction at lower overpotential in comparison to the conventional Cu nanoparticles derived from sole Cu2O. Operando Raman spectroelectrochemistry is employed to in-situ monitor the process of nanoparticles formation during the electrocatalytic process. The experimental data are collaborated with DFT calculations to provide insight into the electro-formation of the type of Cu-based mixed metal oxide catalyst during the CO2 electroreduction, where a formation mechanism via copper ion diffusion across the substrate is suggested.

Operando Raman spectroelectrochemistry: Raman spectra were recorded from the surface of Cu2O/ITO/FTO during one-hour CO2 electroreduction; here the normalization of Raman bands at 109 cm−1 and 136 cm−1, as a function of CO2 electroreduction time presented. The background represents the surface structure of delafossite CuInO2 segregated during one-hour CO2 ER on the surface of Cu2O/ITO/FTO.

March 28: Quentin Daniel, Lele Duan, Brian J. J. Timmer, Hong Chen , Xiaodan Luo, Ram Ambre, Ying Wang, Biaobiao Zhang, Peili Zhang, Lei Wang, Fusheng Li, Junliang Sun, Mårten Ahlquist , and Licheng Sun published an article in ACS Catalysis:

"Water Oxidation Initiated by In Situ Dimerization of the Molecular Ru(pdc) Catalyst."

Abstract: The mononuclear ruthenium complex [Ru(pdc)L3] (H2pdc = 2,6-pyridinedicarboxylic acid, L = N-heterocycles such as 4-picoline) has previously shown promising catalytic efficiency toward water oxidation, both in homogeneous solutions and anchored on electrode surfaces. However, the detailed water oxidation mechanism catalyzed by this type of complex has remained unclear. In order to deepen understanding of this type of catalyst, in the present study, [Ru(pdc)(py)3] (py = pyridine) has been synthesized, and the detailed catalytic mechanism has been studied by electrochemistry, UV–vis, NMR, MS, and X-ray crystallography. Interestingly, it was found that once having reached the RuIV state, this complex promptly formed a stable ruthenium dimer [RuIII(pdc)(py)2-O-RuIV(pdc)(py)2]+. Further investigations suggested that the present dimer, after one pyridine ligand exchange with water to form [RuIII(pdc)(py)2-O-RuIV(pdc)(py)(H2O)]+, was the true active species to catalyze water oxidation in homogeneous solutions.

March 1: Rui Miao, Hao Xie, Felix Ho and Peter Lindblad published an article in Metabolic engineering:

Protein engineering of α-ketoisovalerate decarboxylase for improved isobutanol production in Synechocystis PCC 6803.

AbstractProtein engineering is a powerful tool to modify e.g. protein stability, activity and substrate selectivity. Heterologous expression of the enzyme α-ketoisovalerate decarboxylase (Kivd) in the unicellular cyanobacterium Synechocystis PCC 6803 results in cells producing isobutanol and 3-methyl-1-butanol, with Kivd identified as a potential bottleneck. In the present study, we used protein engineering of Kivd to improve isobutanol production in Synechocystis PCC 6803. Isobutanol is a flammable compound that can be used as a biofuel due to its high energy density and suitable physical and chemical properties. Single replacement, either Val461 to isoleucine or Ser286 to threonine, increased the Kivd activity significantly, both in vivo and in vitro resulting in increased overall production while isobutanol production was increased more than 3-methyl-1-butanol production. Moreover, among all the engineered strains examined, the strain with the combined modification V461I/S286T showed the highest (2.4 times) improvement of isobutanol-to-3M1B molar ratio, which was due to a decrease of the activity towards 3M1B production. Protein engineering of Kivd resulted in both enhanced total catalytic activity and preferential shift towards isobutanol production in Synechocystis PCC 6803.

February 9Ben Johnson, Asamanjoy Bhunia, Honghan Fei, Seth M. Cohen, and Sascha Ott published an article in Journal of the American Chemical Society:

Development of a UiO-Type Thin Film Electrocatalysis Platform with Redox-Active Linkers.


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).

Feb 12. 2018: Andrea Pavlou, Julien Jacques, Nigar Ahmadova, Fikret Mamedov and Stenbjörn Styring published an article in Scientific reports

The wavelength of the incident light determines the primary charge separation pathway in Photosystem II


Charge separation is a key component of the reactions cascade of photosynthesis, by which solar energy is converted to chemical energy. From this photochemical reaction, two radicals of opposite charge are formed, a highly reducing anion and a highly oxidising cation. We have previously proposed that the cation after far-red light excitation is located on a component different from PD1, which is the location of the primary electron hole after visible light excitation. Here, we attempt to provide further insight into the location of the primary charge separation upon far-red light excitation of PS II, using the EPR signal of the spin polarized 3P680 as a probe. We demonstrate that, under far-red light illumination, the spin polarized 3P680 is not formed, despite the primary charge separation still occurring at these conditions. We propose that this is because under far-red light excitation, the primary electron hole is localized on ChlD1, rather than on PD1. The fact that identical samples have demonstrated charge separation upon both far-red and visible light excitation supports our hypothesis that two pathways for primary charge separation exist in parallel in PS II reaction centres. These pathways are excited and activated dependent of the wavelength applied.

Jan. 26: Peili Zhang, Lin Li, Dennis Nordlund, Hong Chen, Lizhou Fan, Biaobiao Zhang, Xia Sheng, Quentin Daniel, and Licheng Sun published an article in Nature communications:

"Dendritic core-shell nickel-iron-copper metal/metal oxide electrode for efficient electrocatalytic water oxidation."


Electrochemical water splitting requires efficient water oxidation catalysts to accelerate the sluggish kinetics of the water oxidation reaction. Here, we report a promisingly dendritic coreshell nickel-iron-copper metal/metal oxide electrode, prepared via dealloying with an electrodeposited nickel-iron-copper alloy as a precursor, as the catalyst for water oxidation. 

Microscopy measurements of the NiFeCu parent alloy. a, b SEM images of NiFeCu alloy on nickel foam. Scale bar in a is 10 µm, in b is 2 µm. c TEM image of NiFeCu tip. Scale bar in c is 500 nm. d–g TEM images of a branch tip and corresponding elemental mappings. Scale bar in d is 100 nm

The as-prepared core-shell nickel-iron-copper electrode is characterized with porous oxide shells
and metallic cores. This tri-metal-based core-shell nickel-iron-copper electrode exhibits a
remarkable activity toward water oxidation in alkaline medium with an overpotential of only
180 mV at a current density of 10 mA cm−2. The core-shell NiFeCu electrode exhibits
pH-dependent oxygen evolution reaction activity on the reversible hydrogen electrode scale,
suggesting that non-concerted proton-electron transfers participate in catalyzing the oxygen
evolution reaction. To the best of our knowledge, the as-fabricated core-shell nickel-ironcopper
is one of the most promising oxygen evolution catalysts.

Jan. 15: Lívia S. Mészáros,  Brigitta Németh, Charlène Esmieu, Pierre Ceccaldi  and Gustav Berggren published an article in Angewandte Chemie International Edition.

In Vivo EPR Characterization of Semi‐Synthetic [FeFe] Hydrogenases.


EPR spectroscopy reveals the formation of two different semi‐synthetic hydrogenases in vivo. [FeFe] hydrogenases are metalloenzymes that catalyze the interconversion of molecular hydrogen and protons. The reaction is catalyzed by the H‐cluster, consisting of a canonical iron–sulfur cluster and an organometallic [2Fe] subsite. It was recently shown that the enzyme can be reconstituted with synthetic cofactors mimicking the composition of the [2Fe] subsite, resulting in semi‐synthetic hydrogenases. Herein, we employ EPR spectroscopy to monitor the formation of two such semi‐synthetic enzymes in whole cells. The study provides the first spectroscopic characterization of semi‐synthetic hydrogenases in vivo, and the observation of two different oxidized states of the H‐cluster under intracellular conditions. Moreover, these findings underscore how synthetic chemistry can be a powerful tool for manipulation and examination of the hydrogenase enzyme under in vivo conditions.

Last updated October 18, 2019