Charge transfer processes involved in photocatalytic hydrogen production over CuO/ZrO2-TiO2 materials

摘要

Co-catalysts are widely employed to boost the photocatalytic hydrogen production; particularly, CuO has shown a remarkable improvement in the reaction rate. However, the impact of CuO on the charge transfer process during photocatalytic water reduction has been barely investigated. In this work, ZrO2-TiO2 (ZT) heterojunctions (5 mol% ZrO2) have been obtained by means of the sol-gel method. Subsequently, copper nitrate impregnations are prepared by an incipient wetness impregnation method to get 0.5, 1, 3 and 5 wt% CuO loadings. A maximum in the photocatalytic activity is observed for the material containing 1 wt% CuO, followed by a drastic drop in the hydrogen generation rate. Electrochemical characterization shows that the charge-transfer resistance controls the photocatalytic experiments together with the additional interfacial resistance. The maximum photocatalytic activity is then given by a compromise between these two parameters. A further increase of the additional resistance, directly proportional to the CuO loading, reduces drastically the photocatalytic behavior most likely due to the electron trapping at the ZT-CuO interface. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.