86446 20200716101512.0 doi 10.1016/j.electacta.2018.12.085 sideral 110361 ART-2019-110361 eng Hernández-Ferrer, J. Photoactivity improvement of TiO2 electrodes by thin hole transport layers of reduced graphene oxide 2019 Access copy available to the general public Unrestricted Nanostructured TiO2 and graphene-based materials constitute components of actual interest in devices related to solar energy conversion and storage. In this work, we show that a thin layer of electrochemically reduced graphene oxide (ECrGO), covering nanostructured TiO2 photoelectrodes, can significantly improve the photoactivity. In order to understand the working principle, ECrGO/TiO2 photoelectrodes with different ECrGO thicknesses were prepared and studied by a set of photoelectrochemical measurements. Methanol in alkaline conditions was employed as effective hole acceptor probe to elucidate the electronic phenomena in the electrode layers and interfaces. These studies underline the hole accepting properties of ECrGO and reveal the formation of a p-n junction at the interface between ECrGO and TiO2. It is shown for the first time that the resulting space charge region of about 10 nm defines the operational functionality of the ECrGO layer. Films thinner than the space charge region act as hole transport layer (HTL), which efficiently transfers holes to the liquid interface thus leading to enhanced photoactivity. Thicker films however act as hole blocking layer (HBL), resulting in a systematic decrease of the photoactivity. The finding of a thickness dependent threshold value for the operation of ECrGO as HTL and HBL is of general interest for the fabrication of optoelectronic devices with improved performance. info:eu-repo/grantAgreement/ES/DGA/T03-17R info:eu-repo/grantAgreement/ES/MINECO/BES-2014-068727 info:eu-repo/grantAgreement/ES/MINECO-FEDER/ENE2016-79282-C5-1-R info:eu-repo/semantics/openAccess All rights reserved http://www.europeana.eu/rights/rr-f/ 6.215 2019 ELECTROCHEMISTRY 5 / 27 = 0.185 2019 Q1 T1 1.467 2019 Electrochemistry 2019 Q1 Chemical Engineering (miscellaneous) 2019 Q1 info:eu-repo/semantics/article info:eu-repo/semantics/acceptedVersion Ansón-Casaos, A. Víctor-Román, S. Sanahuja-Parejo, O. Martínez, M.T. (orcid)0000-0001-9814-0834 Villacampa, B. Universidad de Zaragoza Benito, A.M. Maser, W.K. 2003 395 Universidad de Zaragoza Dpto. Física Materia Condensa. Área Física Materia Condensada 298 (2019), 279-287 Electrochim. acta Electrochimica Acta 0013-4686 494526 http://zaguan.unizar.es/record/86446/files/texto_completo.pdf Postprint 194338 http://zaguan.unizar.es/record/86446/files/texto_completo.jpg?subformat=icon icon Postprint oai:zaguan.unizar.es:86446 articulos driver 2020-07-16-09:19:29 ARTICLE