Nature-Inspired Tree-Like TiO2 Architecture: A 3D Platform for the Assembly of CdS and Reduced Graphene Oxide for Photoelectrochemical Processes

A nature-inspired "tree"-like 3D hierarchical titania/TiO2 architecture was prepared as a façade to strategically assemble reduced graphene oxide/RGO (a facile charge transporter) and cadmium sulfide/CdS (a visible light harvester) is presented for the first time. The core 3D TiO2 heterostructure was prepared using a TiCl3 mediated surface treatment of titania nanorods on fluorine-doped tin oxide (FTO) coated glass-slides. The performance of the 3D TiO2, which varies as a function of the treatment time, was first examined to achieve optimal photoelectrochemical response. Subsequently, the architecture was tested for its (i) theoretical water-splitting potential and (ii) ability to immobilize chalcogenide nonocrystals (CdS) with and without RGO. The best "applied bias to photoconversion efficiency" (% ABPE) was noted to be 0.36% (−0.15 V vs Ag/AgCl) for the TiO2 architecture. A 140% increase with CdS deposition on the branched TiO2 indicated the structures' ability to effectively immobilize the chalcogenide. The effect of RGO on the photoelectrochemical response was explored and an optimum loading (1 mg.mL–1) of RGO was noted to boost the photoresponse by an additional 150% compared to "CdS-only" photoanodes. Further, stability analysis performed over 3 h showed that the presence of RGO significantly delays CdS corrosion-driven deactivation. Finally, the fundamental insights on the impact of RGO in the 3D TiO2/RGO/CdS photoanode and its effect on the charge transportation mechanism were examined using electrochemical impedance spectroscopy.