Probing biological redox chemistry with large amplitude Fourier transformed ac voltammetry

Adamson, Hope; Bond, Alan M.; Parkin, Alison

doi:10.1039/c7cc03870d

Cited by 51 publications

(51 citation statements)

References 91 publications

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“…The high‐order harmonic components (≥4) in FTACV avoid the non‐Faradaic process and signify currents related to electron transfer and catalytic reactions (Figure S21, Supporting Information). [ 23 ] Thus, the 6th harmonic FTACV components of CoFeWO x and reference catalysts at 10 Hz and 100 mV are compared in Figure 4b. Three distinctive sets of peaks can be assigned to different electron transfer steps along the OER pathway.…”

Section: Resultsmentioning

confidence: 99%

Octahedral Coordinated Trivalent Cobalt Enriched Multimetal Oxygen‐Evolution Catalysts

Chen

et al. 2020

Advanced Energy Materials

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overpotential (η) to enable efficient water electrolyzers. [3] Even the most efficient precious-metal-based catalysts require a substantial overpotential. Researchers have explored cobalt oxide (Co 3 O 4), hydroxides (Co(OH) 2), and oxyhydroxides (CoOOH) as catalysts for OER. [4] It has been found that their catalytic performance correlates with the energetics of OER intermediates on active catalytic Co sites. [5] The catalytic activity of Co catalysts can be significantly improved by alloying with other metals, such as Fe, Ni, and Mn, which optimizes the Co d-orbital electronic structure, enabling more efficient adsorption/desorption of OER intermediates. [4c,d,6] Recently, several high-valence metal cations, including W 6+ , Mo 6+ , and V 5+ , have been identified as OER performance boosters for Co catalysts because their empty d-orbitals can efficiently modulate the electronic structure of Co. [6d,5c,7] In particular, a Co-FeW trimetallic metal oxyhydroxide catalyst exhibits one of the lowest overpotential (η 10) of 191 mV (supported on Au plated Ni foams (NiFs) or 223 mV supported on glassy carbon electrodes) at 10 mA cm −2 in alkaline electrolyte, demonstrating a very promising OER catalyst. [5c] In another study, Fe was found to play a critical role in regulating the catalytic activity of Co-FeW oxyhydroxides, and the optimized W 0.5 Co 0.4 Fe 0.1 exhibited an overpotential of 310 mV at 100 mA cm −2. [7b] Furthermore, recent in situ mechanistic studies suggest that Co catalysts would undergo structure transformations during OER to form CoOOH, in which high valence Co ions in the octahedral coordination (Co Oh 3+) serve as active catalytic sites for OER. [8] However, the abundance of Co Oh 3+ in the previously reported Co-FeW oxyhydroxides was not controlled. Thus, we envision that creating Co-FeW oxyhydroxides enriched with Co Oh 3+ may deliver a high-performance catalyst for OER. A key challenge is how to synthesize Co-FeW oxyhydroxides with a high abundance of Co Oh 3+ , which have homogenously dispersed metal components without phase segregation so that different metal atoms can actively interact with each other. The previously used sol-gel method by hydrolyzing the mixture of CoCl 2 , FeCl 3 , and WCl 6 , mainly resulted in Co 2+ species in the resulting Co-FeW oxyhydroxides. [5c] Hydrothermal synthesis involving WCl 6 often leads to the formation of a segregated WO x phase due to the spontaneous hydrolysis. [7b] In comparison, electrodeposition is a versatile technique to synthesize Octahedral coordinated trivalent cobalt cations (Co Oh 3+) in metal oxyhydroxides are highly active catalytic sites for the oxygen evolution reaction (OER), a critical bottleneck for efficient water splitting; however, previous synthetic methods have limited control over these sites. Herein, a scalable electrodeposition method coupled with in situ oxidation to produce amorphous Co-FeW trimetallic oxyhydroxides enriched with Co Oh 3+ is developed. X-ray absorption, in operando spectroscopic analysis, and computational studie...

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Section: Resultsmentioning

confidence: 99%

Octahedral Coordinated Trivalent Cobalt Enriched Multimetal Oxygen‐Evolution Catalysts

Chen

et al. 2020

Advanced Energy Materials

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“…With the FTacV method, the redox response can be isolated from all the factors that affect the signal, so it can be used even with low enzyme concentrations [ 28 ]. Moreover, FTacV allows for tracking the e − transfer stages of an electrochemical reaction at various conditions of temperature and pH, which renders this method suitable for studying the activity of enzymes [ 29 , 30 ]. This method has been used for the first time by Zouraris et al to evaluate the redox potential of LPMOs by monitoring the direct e − transfer between the enzyme and a glassy carbon electrode after LPMO immobilization in Nafion polyelectrolyte [ 31 ].…”

Section: Introductionmentioning

confidence: 99%

Effect of lignin fractions isolated from different biomass sources on cellulose oxidation by fungal lytic polysaccharide monooxygenases

Muraleedharan

Zouraris

Karantonis

et al. 2018

Biotechnol Biofuels

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BackgroundLytic polysaccharide monooxygenases (LPMOs) are copper-dependent enzymes that oxidatively cleave recalcitrant lignocellulose in the presence of oxygen or hydrogen peroxide as co-substrate and a reducing agent as electron donor. One of the possible systems that provide electrons to the LPMOs active site and promote the polysaccharide degradation involves the mediation of phenolic agents, such as lignin, low-molecular-weight lignin-derived compounds and other plant phenols. In the present work, the interaction of the bulk insoluble lignin fraction extracted from pretreated biomass with LPMOs and the ability to provide electrons to the active site of the enzymes is studied.ResultsThe catalytic efficiency of three LPMOs, namely MtLPMO9 with C1/C4 regioselectivity, PcLPMO9D which is a C1 active LPMO and NcLPMO9C which is a C4 LPMO, was evaluated in the presence of different lignins. It was correlated with the physicochemical and structural properties of lignins, such as the molecular weight and the composition of aromatic and aliphatic hydroxyl groups. Moreover, the redox potential of lignins was determined with the use of large amplitude Fourier Transform alternating current cyclic voltammetry method and compared to the formal potential of the Cu (II) center in the active site of the LPMOs, providing more information about the lignin-LPMO interaction. The results demonstrated the existence of low-molecular weight lignin-derived compounds that are diffused in the reaction medium, which are able to reduce the enzyme active site and subsequently utilize additional electrons from the insoluble lignin fraction to promote the LPMO oxidative activity. Regarding the bulk lignin fractions, those isolated from the organosolv pretreated materials served as the best candidates in supplying electrons to the soluble compounds and, finally, to the enzymes. This difference, based on biomass pretreatment, was also demonstrated by the activity of LPMOs on natural substrates in the presence and absence of ascorbic acid as additional reducing agent.ConclusionsLignins can support the action of LPMOs and serve indirectly as electron donors through low-molecular-weight soluble compounds. This ability depends on their physicochemical and structural properties and is related to the biomass source and pretreatment method.Electronic supplementary materialThe online version of this article (10.1186/s13068-018-1294-6) contains supplementary material, which is available to authorized users.

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“…Electrochemistry, EPR and ideally X‐ray crystallography data is then required to underpin more extensive calculations. Ideally, we would like to use the more sophisticated technique of Fourier transform large amplitude alternating current voltammetry to interrogate such variants, since this may enable measurement of the iron sulfur cluster redox transitions ,…”

Section: Figurementioning

confidence: 99%

Conserved Histidine Adjacent to the Proximal Cluster Tunes the Anaerobic Reductive Activation of Escherichia coli Membrane‐Bound [NiFe] Hydrogenase‐1

et al. 2018

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Abstract[NiFe] hydrogenases are electrocatalysts that oxidize H2 at a rapid rate without the need for precious metals. All membrane‐bound [NiFe] hydrogenases (MBH) possess a histidine residue that points to the electron‐transfer iron sulfur cluster closest (“proximal”) to the [NiFe] H2‐binding active site. Replacement of this amino acid with alanine induces O2 sensitivity, and this has been attributed to the role of the histidine in enabling the reversible O2‐induced over‐oxidation of the [Fe4S3Cys2] proximal cluster possessed by all O2‐tolerant MBH. We have created an Escherichia coli Hyd‐1 His‐to‐Ala variant and report O2‐free electrochemical measurements at high potential that indicate the histidine‐mediated [Fe4S3Cys2] cluster‐opening/closing mechanism also underpins anaerobic reactivation. We validate these experiments by comparing them to the impact of an analogous His‐to‐Ala replacement in Escherichia coli Hyd‐2, a [NiFe]‐MBH that contains a [Fe4S4] center.

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Probing biological redox chemistry with large amplitude Fourier transformed ac voltammetry

Abstract: A review of the insight into biological redox chemistry which has been enabled by the development of large amplitude Fourier transform ac voltammetry.

Cited by 51 publications

References 91 publications

Octahedral Coordinated Trivalent Cobalt Enriched Multimetal Oxygen‐Evolution Catalysts

Octahedral Coordinated Trivalent Cobalt Enriched Multimetal Oxygen‐Evolution Catalysts

Effect of lignin fractions isolated from different biomass sources on cellulose oxidation by fungal lytic polysaccharide monooxygenases

Conserved Histidine Adjacent to the Proximal Cluster Tunes the Anaerobic Reductive Activation of Escherichia coli Membrane‐Bound [NiFe] Hydrogenase‐1

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