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dc.contributor.authorRos, Carleses_ES
dc.contributor.authorCarretero, Nina M.es_ES
dc.contributor.authorDavid, Jeremyes_ES
dc.contributor.authorArbiol, Jordies_ES
dc.contributor.authorAndreu, Teresaes_ES
dc.contributor.authorMorante, Joan Ramones_ES
dc.identifier.citationACS Applied Materials and Interfaces 11(33): 29725-29735 (2019)es_ES
dc.description.abstractAround 100 nm thick TiO2 layers deposited by atomic layer deposition (ALD) have been investigated as anticorrosion protective films for silicon-based photoanodes decorated with 5 nm NiFe catalyst in highly alkaline electrolyte. Completely amorphous layers presented high resistivity; meanwhile, the ones synthesized at 300 °C, having a fully anatase crystalline TiO2 structure, introduced insignificant resistance, showing direct correlation between crystallization degree and electrical conductivity. The conductivity through crystalline TiO2 layers has been found not to be homogeneous, presenting preferential conduction paths attributed to grain boundaries and defects within the crystalline structure. A correlation between the conductivity atomic force microscopy measurements and grain interstitials can be seen, supported by high-resolution transmission electron microscopy cross-sectional images presenting defective regions in crystalline TiO2 grains. It was found that the conduction mechanism goes through the injection of electrons coming from water oxidation from the electrocatalyst into the TiO2 conduction band. Then, electrons are transported to the Si/SiOx/TiO2 interface where electrons recombine with holes given by the p+n-Si junction. No evidences of intra-band-gap states in TiO2 responsible of conductivity have been detected. Stability measurements of fully crystalline samples over 480 h in anodic polarization show a continuous current decay. Electrochemical impedance spectroscopy allows to identify that the main cause of deactivation is associated with the loss of TiO2 electrical conductivity, corresponding to a self-passivation mechanism. This is proposed to reflect the effect of OH– ions diffusing in the TiO2 structure in anodic conditions by the electric field. This fact proves that a modification takes place in the defective zone of the layer, blocking the ability to transfer electrical charge through the layer. According to this mechanism, a regeneration of the degradation process is demonstrated possible based on ultraviolet illumination, which contributes to change the occupancy of TiO2 electronic states and to recover the defective zone’s conductivity. These findings confirm the connection between the structural properties of the ALD-deposited polycrystalline layer and the degradation mechanisms and thus highlight main concerns toward fabricating long-lasting metal-oxide protective layers for frontal illuminated photoelectrodes.es_ES
dc.description.sponsorshipThis work was partially supported by Repsol S.A. and Enagas S.A. Authors from IREC acknowledge Generalitat de Catalunya for financial support through the CERCA Programme, M2E (2017SGR1246), and XaRMAE network. IREC also acknowledges additional support by the European Regional Development Funds (ERDF, FEDER) and by MINECO coordinated projects MAT2014-59961-C2, ENE2017-85087-C3 (IREC/ICN2) and ENE2016-80788-C5-5-R. C.R. acknowledges MINECO for his FPI grant (BES-2015-071618). ICN2 acknowledge funding from Generalitat de Catalunya 2017 SGR 327. ICN2 was supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706) and was funded by the CERCA Programme/Generalitat de Catalunya. J.D. received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 665919 (P-SPHERE) co-funded by Severo Ochoa Programme.es_ES
dc.publisherAmerican Chemical Societyes_ES
dc.titleInsight into the degradation mechanisms of atomic layer deposited TiO2 as photoanode protective layeres_ES
dc.description.peerreviewedPeer reviewedes_ES
dc.contributor.funderAgencia Estatal de Investigación (España)-
dc.contributor.funderAgencia Estatal de Investigación (España)-
dc.contributor.funderGeneralitat de Catalunyaes_ES
dc.contributor.funderEuropean Commissiones_ES
dc.contributor.funderMinisterio de Economía y Competitividad (España)es_ES
dc.contributor.funderMinisterio de Ciencia, Innovación y Universidades (España)es_ES
oprm.item.hasRevisionno ko 0 false*
dc.contributor.orcidRos, Carles [0000-0002-9148-2767]es_ES
dc.contributor.orcidArbiol, Jordi [0000-0002-0695-1726]es_ES
dc.contributor.orcidAndreu, Teresa [0000-0002-2804-4545]es_ES
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