Self-assembled TiO2 agglomerates hybridized with reduced-graphene oxide: A high-performance hybrid photocatalyst for solar energy conversion

Spherical TiO2 agglomerates incorporated with reduced-graphene oxide (rGO) sheets were fabricated using aerosol assisted self-assembly. Compared to that of conventional graphene-TiO2 composites, the new hybrid geometry of the self-assembled agglomeration of TiO2 and rGO enabled a porous structure, a more efficient charge separation through interconnected TiO2 nanoparticles and rGO, and improved the contact between TiO2 and rGO to maximize the role of rGO as an electron reservoir. The as-prepared rGO-TiO2 composites were characterized with a diverse range of analytical techniques, and their photocatalytic activity was tested in terms of H-2 production and gaseous CH3CHO degradation. The incorporation of the rGO sheets into the TiO2 agglomerates promoted the photocatalytic H-2 production and CH3CHO oxidation; our results showed that the performance of our systems is directly proportional to the content of rGO (when added up to 10 wt%). This finding confirmed that rGO, acting as an electron collector and mediator, can facilitate charge-pair separation; only a small light-shielding effect by rGO was observed. Furthermore, open-circuit potential decay measurements revealed that the presence of rGO in the agglomerated TiO2 can significantly suppress charge recombination; this further confirmed the role of rGO as an effective electron conduit. The new geometry of the rGO-TiO2 composite proposed in this work shows several advantages compared to various types of graphene-TiO2 composites previously reported, such as the stronger electronic coupling between rGO sheets and TiO2, minimized light-shielding effect by rGO (even when a relatively large amount of rGO is used), and facile scale-up for mass production. Therefore, our rGO-TiO2 composite can be considered as a promising hybrid photocatalyst for solar energy conversion. (C) 2014 Elsevier B.V. All rights reserved.