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- Cheng, Fangwen, et al.
(författare)
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Embedding biocatalysts in a redox polymer enhances the performance of dye-sensitized photocathodes in bias-free photoelectrochemical water splitting
- 2024
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- Dye-sensitized photoelectrodes consisting of photosensitizers and molecular catalysts with tunable structures and adjustable energy levels are attractive for low-cost and eco-friendly solar-assisted synthesis of energy rich products. Despite these advantages, dye-sensitized NiO photocathodes suffer from severe electron-hole recombination and facile molecule detachment, limiting photocurrent and stability in photoelectrochemical water-splitting devices. In this work, we develop an efficient and robust biohybrid dye-sensitized NiO photocathode, in which the intermolecular charge transfer is enhanced by a redox polymer. Owing to efficient assisted electron transfer from the dye to the catalyst, the biohybrid NiO photocathode showed a satisfactory photocurrent of 141±17 μA·cm−2 at neutral pH at 0 V versus reversible hydrogen electrode and a stable continuous output within 5 h. This photocathode is capable of driving overall water splitting in combination with a bismuth vanadate photoanode, showing distinguished solar-to-hydrogen efficiency among all reported water-splitting devices based on dye-sensitized photocathodes. These findings demonstrate the opportunity of building green biohybrid systems for artificial synthesis of solar fuels.
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- Gamache, Mira T., et al.
(författare)
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E. coli-based semi-artificial photosynthesis : biocompatibility of redox mediators and electron donors in [FeFe] hydrogenase driven hydrogen evolution
- 2023
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Ingår i: ENERGY ADVANCES. - : Royal Society of Chemistry. - 2753-1457. ; 2:12, s. 2085-2092
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Tidskriftsartikel (refereegranskat)abstract
- Semi-artificial photosynthesis aims to harness the power of biocatalysis while breaking away from the limitations of Nature's photosynthetic machinery, by merging artificial light harvesters with enzyme catalysts. However, the artificial photocatalytic components are generally toxic towards the biological components. In this study, we investigate a system wherein Escherichia coli cells, heterologously expressing an [FeFe] hydrogenase, act as hydrogen evolution catalyst in combination with an artificial photosensitizer, sacrificial electron donor, and redox mediator. Previously, the use of artificial components or their reaction products was found to be toxic to E. coli cells. To overcome this challenge, we examined alternative electron donors and redox mediators, achieving turnover numbers (TON, 39.6 mu mol H-2 per 1 mL sample with OD600 = 5) and turnover frequencies (TOF, 812 nmol H-2 h(-1) per 1 mL sample with OD600 = 5) on par with previously reported high performing E. coli-based systems while greatly reducing cytotoxic effects. Transient absorption spectroscopy revealed how the choice of photosensitizer, electron donor, and redox mediator affects the observed photocatalytic TOFs. Following optimization of the redox mediator and electron donor the biocatalyst demonstrated remarkable stability throughout the experiments. We identified the availability of electrons from the electron donor as the primary limiting factor, with approximately 85% of electrons being effectively utilized for hydrogen production. Furthermore, the observed activity with different [FeFe] hydrogenases verified the broad applicability of the identified photocatalytic components to promote light-driven catalysis in bio-hybrid systems.
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- Gamache, Mira T., et al.
(författare)
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Elucidating Electron Transfer Kinetics and Optimizing System Performance for Escherichia coli-Based Semi-Artificial H-2 Production
- 2023
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Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435 .- 2155-5435. ; 13:14, s. 9476-9486
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Tidskriftsartikel (refereegranskat)abstract
- Both photo- and biocatalysis are well-established andintensivelystudied. The combination of these two approaches is also an emergingresearch field, commonly referred to as semi-artificial photosynthesis.Semi-artificial photosynthesis aims at combining highly efficientsynthetic light harvesters with the self-healing and potent catalyticproperties of biocatalysis. In this study, a semi-artificial photocatalyticsystem featuring Escherichia coli bacteria,which heterologously express the [FeFe] hydrogenase enzyme HydA1 fromgreen algae, is employed as a hydrogen gas production catalyst. Toprobe the influence of photochemistry on overall system performance,the E. coli whole-cell catalyst iscombined with two different photosensitizers and redox mediators.The addition of a redox mediator greatly improves the rates and longevityof the photocatalytic system, as reflected in increases of both theturn-over number (0.777 vs 10.9 & mu;mol H-2 mL(-1) OD600 (-1)) and the turn-over frequency(175 vs 334 & mu;mol H-2 mL(-1) h(-1) OD600 (-1)). The redoxmediator is found to both protect from photobleaching and enable electrontransport to the hydrogenase from an extracellular photosensitizer.However, E. coli cells are stronglyaffected by the photocatalytic system, leading to a decrease in cellintegrity and cell viability, possibly due to toxic decompositionproducts formed during the photocatalytic process. We furthermoreemployed steady-state and transient absorption spectroscopy to investigatesolution potentials and the kinetics of electron transfer processesbetween the sacrificial electron donor, photosensitizer, redox mediator,and the [FeFe] hydrogenase as the final electron acceptor. These resultsallowed us to rationalize the different activities observed in photocatalyticassays and offer a better understanding of the factors that influencethe photocatalytic performance of E. coli-based whole-cell systems.
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- Johnson, Ben A.
(författare)
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Interrogating Diffusional Mass and Charge Transport in Catalytic Metal-Organic Frameworks
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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