Artificial photosynthesis at soft interfaces.

The concept of artificial photosynthesis at a polarised liquid membrane is presented. It includes two photosystems, one at each interface for the hydrogen and oxygen evolution respectively. Both reactions involve proton coupled electron transfer reactions, and some ultrafast steps at the photosensitization stage.

Hydrogen evolution catalyzed by electrodeposited nanoparticles at the liquid/liquid interface.

Aqueous protons reduction by decamethylferrocene in 1,2-dichloroethane can be catalyzed efficiently by platinum and palladium nanoparticles electrogenerated in situ at the liquid-liquid interface.

Molecular electrocatalysis at soft interfaces.

The fundamental aspects of electrochemistry at liquid-liquid interfaces are introduced to present the concept of molecular electrocatalysis. Here, a molecular catalyst is adsorbed at the interface to promote a proton coupled electron transfer reaction such as hydrogen evolution or oxygen reduction using lipophilic electron donors.

Oxygen reduction catalyzed by a fluorinated tetraphenylporphyrin free base at liquid/liquid interfaces.

The diprotonated form of a fluorinated free base porphyrin, namely 5-(p-aminophenyl)-10,15,20-tris(pentafluorophenyl)porphyrin (H(2)FAP), can catalyze the reduction of oxygen by a weak electron donor, namely ferrocene (Fc). At a water/1,2-dichloroethane interface, the interfacial formation of H(4)FAP(2+) is observed by UV-vis spectroscopy and ion-transfer voltammetry, due to the double protonation of H(2)FAP at the imino nitrogen atoms in the tetrapyrrole ring. H(4)FAP(2+) is shown to bind oxygen, and the complex in the organic phase can easily be reduced by Fc to produce hydrogen peroxide as studied by two-phase reactions with the Galvani potential difference between the two phases being controlled by the partition of a common ion. Spectrophotometric measurements performed in 1,2-dichloroethane solutions clearly evidence that reduction of oxygen by Fc catalyzed by H(4)FAP(2+) only occurs in the presence of the tetrakis(pentafluorophenyl)borate (TB(-)) counteranion in the organic phase. Finally, ab initio computations support the catalytic activation of H(4)FAP(2+) on oxygen.

Oxygen and proton reduction by decamethylferrocene in non-aqueous acidic media.

Experimental studies and density functional theory (DFT) computations suggest that oxygen and proton reduction by decamethylferrocene (DMFc) in 1,2-dichloroethane involves protonated DMFc, DMFcH(+), as an active intermediate species, producing hydrogen peroxide and hydrogen in aerobic and anaerobic conditions, respectively.

Molecular electrocatalysis for oxygen reduction by cobalt porphyrins adsorbed at liquid/liquid interfaces.

Molecular electrocatalysis for oxygen reduction at a polarized water/1,2-dichloroethane (DCE) interface was studied, involving aqueous protons, ferrocene (Fc) in DCE and amphiphilic cobalt porphyrin catalysts adsorbed at the interface. The catalyst, (2,8,13,17-tetraethyl-3,7,12,18-tetramethyl-5-p-amino-phenylporphyrin) cobalt(II) (CoAP), functions like conventional cobalt porphyrins, activating O(2) via coordination by the formation of a superoxide structure. Furthermore, due to the hydrophilic nature of the aminophenyl group, CoAP has a strong affinity for the water/DCE interface as evidenced by lipophilicity mapping calculations and surface tension measurements, facilitating the protonation of the CoAP-O(2) complex and its reduction by ferrocene. The reaction is electrocatalytic as its rate depends on the applied Galvani potential difference between the two phases.

Immobilization of oxime derivative on silica gel for the preparation of new adsorbent.

A new silica gel compound modified 4,4'-oxy-bis(chlorophenylglyoxime) (CPGO) was synthesized and characterized by infrared spectroscopy, elemental analysis and thermogravimetric analysis. The sorption capacity of such a matrix towards Co(II), Ni(II) and Cu(II) from aqueous solutions was studied. The optimum pH values for the separation of these divalent cations on the sorbent were 5.0, 6.0 and 6.0 for Cu, Co and Ni, respectively. The process of metal separation was followed by batch method, and fitted to a Langmuir and Freundlich sorption isotherms. The maximum sorption capacities (0.055, 0.042, and 0.034 mmol g(-1)) were found from the Langmuir equation and the enthalpies of binding were 44.96, 71.63, and 68.14 kJ mol(-1) for Cu, Co and Ni, respectively. The other thermodynamic parameters calculated from the adsorption results were used to explain the mechanism of the adsorption. For example, the Gibbs free energies of binding agree with the spontaneity of the proposed reaction between cations and basic centers.

Proton-coupled oxygen reduction at liquid-liquid interfaces catalyzed by cobalt porphine.

Cobalt porphine (CoP) dissolved in the organic phase of a biphasic system is used to catalyze O(2) reduction by an electron donor, ferrocene (Fc). Using voltammetry at the interface between two immiscible electrolyte solutions (ITIES), it is possible to drive this catalytic reduction at the interface as a function of the applied potential difference, where aqueous protons and organic electron donors combine to reduce O(2). The current signal observed corresponds to a proton-coupled electron transfer (PCET) reaction, as no current and no reaction can be observed in the absence of either the aqueous acid, CoP, Fc, or O(2).

Hydrogen evolution at liquid-liquid interfaces.

Blowing bubbles: Hydrogen evolution by proton reduction with [(C(5)Me(5))(2)Fe] occurs at a soft interface between water and 1,2-dichloroethane (DCE). The reaction proceeds by proton transfer assisted by [(C(5)Me(5))(2)Fe] across the water-DCE interface with subsequent proton reduction in DCE. The interface essentially acts as a proton pump, allowing hydrogen evolution by directly using the aqueous proton.