title: Adsorption Behavior of I3-and I-Ions at a Nanoporous NiO/Acetonitrile Interface Studied by X-ray Photoelectron Spectroscopy.
abstract: The adsorption of I-and I3-anions, i.e., the two species constituting the most common redox couple of dye-sensitized solar cells (DSCs), onto the surface of screen-printed nanoporous NiO was studied by means of X-ray photoelectron spectroscopy (XPS). Nanoporous NiO films were deposited on transparent metallic fluorine-doped tin oxide (FTO) and polarized as working electrodes in a three-electrode cell with differently concentrated I-/I3-electrolytes to simulate the different conditions experienced by the NiO cathodes during the lifecycle of a p-type DSC (p-DSC) at those atomic sites not passivated by the dye. Bare NiO films were tested also as photocathodes of nonsensitized p-DSCs. The ex situ XPS analysis of I 4d ionization region of both reference and electrochemically treated NiO films showed that the presence of native and electrochemically generated Ni3+and Ni4+centers induces fast adsorption/desorption of I-ions and catalyzes their oxidation to I3-ions. The adsorption phenomena generated by I-and I3-species on nanoporous NiO electrodes can also induce an effect of electrochemical passivation toward a fraction of charged Ni sites. Such an effect would render these sites inactive for the further realization of those photoelectrochemical processes at the basis of the operation of a p-DSC.
authors: Department of Chemistry, University of Rome "La Sapienza" , P.zza A. Moro 5, 00185 Rome, Italy.
authors: Matteo
authors: M
authors: Bonomo
authors: Department of Chemistry, University of Rome "La Sapienza" , P.zza A. Moro 5, 00185 Rome, Italy.
authors: Danilo
authors: D
authors: Dini
authors: Department of Chemistry, University of Rome "La Sapienza" , P.zza A. Moro 5, 00185 Rome, Italy.
authors: Andrea G
authors: AG
authors: Marrani