Enhanced photoelectrochemical water splitting characteristics of TiO2 hollow porous spheres by embedding graphene as an electron transfer channel

The generation of renewable solar fuel through photoelectrochemical water splitting is hindered by the inability to identify the right material with the optimum optical, electrical and chemical characteristics. Herein, we demonstrate the ability to fabricate TiO2 hollow porous spheres (HPS)/graphene (Gr) hybrid composite photoanodes for use in solar fuel generation cells. The fabricated materials were characterized by X-ray diffraction, Raman spectroscopy, UV-Vis diffuse reflectance spectroscopy, photoluminescence (PL), scanning electron microscopy and electrochemical techniques. Upon the use of the TiO2 HPS/Gr photoanodes to split water photoelectrochemically under AM 1.5 illumination in 1.0 M KOH aqueous electrolyte, the performance increased with increasing the Gr content, showing a ten-fold increase in the photocurrent for the photoanode containing 5% Gr (1.449 mA cm(-2)) as compared to bare TiO2 HPS (0.143 mA cm(-2)). This enhancement is attributed to the effect of Gr in suppressing the recombination of charge carriers, as supported by the PL measurements and the decrease in the dark current upon the addition of Gr, which acts as an electron acceptor and transports electrons more efficiently. Moreover, the transient photocurrent (J-t) tests confirm the stability of the hybrid photoanodes. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.