Self-Assembled Molecular Rafts at Liquid|Liquid Interfaces for Four-Electron Oxygen Reduction

Olaya, Astrid J.; Schaming, Delphine; Brevet, Pierre-Francois; Nagatani, Hirohisa; Zimmermann, Tomáš; Vaníček, Jiří; Xu, Haijun; Gros, Claude P.; Barbe, Jean‐Michel; Girault, Hubert H.

doi:10.1021/ja2087322

Cited by 85 publications

(80 citation statements)

References 51 publications

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“…If we assume that back-reactions are negligible, the current i 1 for the reduction half-reaction (eq 6) is (8) where k 1 0 is the potential-independent rate constant, A 1 is the area available for reaction 6 being either that of a single NP or of an "island" of electronically interacting NPs, R 1 is the charge transfer coefficient (commonly close to 0.5), and c O 1 w,s is the surface concentration of O 1 in the aqueous phase. Note that the oxidative current is defined as positive, in accordance with IUPAC definitions, and the Fermi level of electrons in solutions is expressed as defined in eqs 2 and 3.…”

Section: Resultsmentioning

confidence: 99%

Interfacial Redox Catalysis on Gold Nanofilms at Soft Interfaces

et al. 2015

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Soft or “liquid–liquid” interfaces were functionalized by roughly half a monolayer of mirror-like nanofilms of gold nanoparticles using a precise interfacial microinjection method. The surface coverage of the nanofilm was characterized by ion transfer voltammetry. These gold nanoparticle films represent an ideal model system for studying both the thermodynamic and kinetic aspects of interfacial redox catalysis. The electric polarization of these soft interfaces is easily controllable, and thus the Fermi level of the electrons in the interfacial gold nanoparticle film can be easily manipulated. Here, we study interfacial redox catalysis between two redox couples located in adjacent immiscible phases and highlight the catalytic properties of a gold nanoparticle film toward heterogeneous electron transfer reactions.

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Section: Resultsmentioning

confidence: 99%

Interfacial Redox Catalysis on Gold Nanofilms at Soft Interfaces

et al. 2015

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“…The IT step can be catalysed by the presence of various aniline derivatives [9,30] and free-base-or metalloporphyrins [44,45], porphines [42] or phthalocyanines [31] in the organic phase and the desired reduction product (H 2 O versus H 2 O 2 ) can be favoured by interfacial assemblies of cobalt porphyrins [12,32,33] or choice of electron donor [10]. Recently, biphasic O 2 reduction has been achieved under neutral and alkaline conditions [17].…”

Section: Biphasic O 2 Reduction By the Ion Transfer -Electron Transfementioning

confidence: 99%

“…Whereas several reports have highlighted the catalysis of biphasic reactions by (i) facilitating the transfer of protons [12,30,31], or other ions [17], across the soft interface and (ii) the use of interfacial species, either molecular [12,32,33] or solid particulates [22,26], to coordinate reactants to enable electrocatalysis, far less common is (iii) the use of NPs as bipolar electrodes to facilitate catalysis via direct interfacial electron transfer (IET) between a lipophilic electron donor and a hydrophilic electron acceptor or vice versa [8]. Such a process is termed interfacial redox catalysis.…”

Section: Introductionmentioning

confidence: 99%

Gold Nanofilm Redox Catalysis for Oxygen Reduction at Soft Interfaces

Smirnov

Peljo

Scanlon

et al. 2016

Electrochimica Acta

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A B S T R A C TFunctionalization of a soft or liquid-liquid interface by a one gold nanoparticle thick "nanofilm" provides a conductive pathway to facilitate interfacial electron transfer from a lipophilic electron donor to a hydrophilic electron acceptor in a process known as interfacial redox catalysis. The gold nanoparticles in the nanofilm are charged by Fermi level equilibration with the lipophilic electron donor and act as an interfacial reservoir of electrons. Additional thermodynamic driving force can be provided by electrochemically polarising the interface. Using these principles, the biphasic reduction of oxygen by a lipophilic electron donor, decamethylferrocene, dissolved in a,a,a-trifluorotoluene was catalysed at a gold nanoparticle nanofilm modified water-oil interface. A recently developed microinjection technique was utilised to modify the interface reproducibly with the mirror-like gold nanoparticle nanofilm, while the oxidised electron donor species and the reduction product, hydrogen peroxide, were detected by ion transfer voltammetry and UV/vis spectroscopy, respectively. Metallization of the soft interface allowed the biphasic oxygen reduction reaction to proceed via an alternative mechanism with enhanced kinetics and at a significantly lower overpotential in comparison to a bare soft interface. Weaker lipophilic reductants, such as ferrocene, were capable of charging the interfacial gold nanoparticle nanofilm but did not have sufficient thermodynamic driving force to significantly elicit biphasic oxygen reduction.

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“…In biphasic systems, the organic phase is saturated with water and in such conditions another type of dimer (water-sandwich dimer B in Fig. 3) can be considered in which a water molecule is incorporated in the cavity between two osmocenium ions according to reactions [7] or [13],…”

Section: Dft Computationsmentioning

confidence: 99%

“…More generally, we have shown that voltammetry at the interface between two immiscible electrolyte solutions (ITIES) is a very useful tool to study proton coupled electron transfer reactions involving aqueous protons and organic electron donors (8)(9)(10). This methodology has been also applied to molecular electrocatalysis where an amphiphilic catalyst is used to complex oxygen to facilitate its reduction as recently reviewed (10)(11)(12)(13).…”

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confidence: 99%

Biphasic water splitting by osmocene

Todorova

Patır

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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The photochemical reactivity of osmocene in a biphasic waterorganic solvent system has been investigated to probe its water splitting properties. The photoreduction of aqueous protons to hydrogen under anaerobic conditions induced by osmocene dissolved in 1,2-dichloroethane and the subsequent water splitting by the osmocenium metal-metal dimer formed during H 2 production were studied by electrochemical methods, UV-visible spectrometry, gas chromatography, and nuclear magnetic resonance spectroscopy. Density functional theory computations were used to validate the reaction pathways.S olar water splitting is undoubtedly a key challenge (1-3), and in the quest for solar fuels, hydrogen is definitely a major target with many industrial applications ranging from transportation to carbon dioxide mitigation (4).Interestingly, some transition metal complexes like metallocenes have been reported to reduce protons to hydrogen. In 1988, cobaltocene was found to produce hydrogen in strong acidic solutions. The mechanism was investigated by pulse radiolysis, and it was found that the reaction kinetics was first order with respect to cobaltocene and the protons pointing to a protonation of the metal as the primary step (5). In 2009, Kunkely and Vogler reported that osmocene dissolved in strong acidic solutions could photogenerate hydrogen and that ½Cp 2 Os IV ðOH − Þ þ could photogenerate oxygen (6). Proton reduction was shown to proceed also by the formation of a hydride followed under UV light by the formation of H 2 and the dimer ½Cp 2 Os III -Os III Cp 2 2þ .One of the major difficulties in studying water splitting by metallocenes is their very poor solubility in aqueous or even acidic solutions. When investigating the reduction of protons in organic phases where metallocenes are soluble, the other major drawback is the low solubility and dissociation of acids in organic solvents. One way to circumvent these issues is to carry out these reactions in biphasic systems.In 2008, we studied the reduction of aqueous protons by decamethylferrocene (DMFc) in 1,2-dichloroethane (1,2-DCE), and, here again the data suggested that the first step is the protonation of the metal (7). In particular, we have shown that hydrogen bubbles can form at the interface and that hydrogen production is associated to the oxidation of the electron donor DMFc. More generally, we have shown that voltammetry at the interface between two immiscible electrolyte solutions (ITIES) is a very useful tool to study proton coupled electron transfer reactions involving aqueous protons and organic electron donors (8-10). This methodology has been also applied to molecular electrocatalysis where an amphiphilic catalyst is used to complex oxygen to facilitate its reduction as recently reviewed (10-13).In this study, the photochemical reactivity of osmocene with water in biphasic systems has been investigated by electrochemical methods on solid electrodes and soft liquid-liquid interfaces to unravel the multistep reaction mechanisms. Density functional theory (DFT)...

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Self-Assembled Molecular Rafts at Liquid|Liquid Interfaces for Four-Electron Oxygen Reduction

Cited by 85 publications

References 51 publications

Interfacial Redox Catalysis on Gold Nanofilms at Soft Interfaces

Interfacial Redox Catalysis on Gold Nanofilms at Soft Interfaces

Gold Nanofilm Redox Catalysis for Oxygen Reduction at Soft Interfaces

Biphasic water splitting by osmocene

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