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Understanding charge transfer dynamics through the ligand shell of colloidal nanoparticles has been an important pursuit in solar energy conversion. While charge transport through ligand shells of nanoparticle films has been studied intensely in static dry and electrochemical systems, its influence on charge transfer kinetics in dispersed colloidal systems has received relatively less attention. This work reports the oxidation of amine passivated tungsten oxide nanoparticles by an organically soluble tris-(1,10-phenanthroline) iron(III) derivative. By following the rate of this oxidation optically via the production of the ferroin derivative under various reaction conditions and particle derivatizations, we are able to show that the fluxional ligand shells on dispersed, colloidal nanoparticles provide a separate and more facile pathway for charge transfer, in which the rate-limiting step for charge transfer is the ligand dissociation. Since such ligand shells are frequently required for nanoparticle stability, this observation has significant implications for colloidal nanoparticle photocatalysis.

A cobalt-sulfide (Co-S) film prepared via electrochemical deposition on conductive substrates is shown to behave as an efficient and robust catalyst for electrochemical and photoelectrochemical hydrogen generation from neutral pH water. Electrochemical experiments demonstrate that the film exhibits a low catalytic onset overpotential (η) of 43 mV, a Tafel slope of 93 mV/dec, and near 100% Faradaic efficiency in pH 7 phosphate buffer. Catalytic current densities can approach 50 mA/cm(2) and activity is maintained for at least 40 h. The catalyst can also be electrochemically coated on silicon, rendering a water-compatible photoelectrochemical system for hydrogen production under simulated 1 sun illumination. The facile preparation of this Co-S film, along with its low overpotential, high activity, and long-term aqueous stability, offer promising features for potential use in solar energy applications.

Understanding chargetransfer dynamics through the ligand shellof colloidal nanoparticles has been an important pursuit in solarenergy conversion. While charge transport through ligand shells ofnanoparticle films has been studied intensely in static dry and electrochemicalsystems, its influence on charge transfer kinetics in dispersed colloidalsystems has received relatively less attention. This work reportsthe oxidation of amine passivated tungsten oxide nanoparticles byan organically soluble tris-(1,10-phenanthroline) ironIIIderivative. By following the rate of this oxidation optically viathe production of the ferroin derivative under various reaction conditionsand particle derivatizations, we are able to show that the fluxionalligand shells on dispersed, colloidal nanoparticles provide a separateand more facile pathway for charge transfer, in which the rate-limitingstep for charge transfer is the ligand dissociation. Since such ligandshells are frequently required for nanoparticle stability, this observationhas significant implications for colloidal nanoparticle photocatalysis. [ABSTRACT FROM AUTHOR]