## 2 Morphology Design of Graphene-Based Composites
### Titania-Graphene Composites (Not Faceted Titania)  
In addition to faceted titania particles, other titania samples with different morphologies have been widely studied for modification with G/rGO/CO, such as nanotubes, nanowires, nanofilms, etc. For example, [PERSON] et al. have prepared photoelectrode composed of titania nanotube arrays (NTAs) modified with ultra-thin G nanosheet (rGO/TiO\({}_{2}\)), as shown in Figure 8. It has been found that the hybridization of ultra-thin rGO nanosheets has resulted in negative shift of the flat band potential of titania, improving efficiency of charge separation and causing the superior photoelectrocatalytic (PEC) performance [25]. Additionally, it has been shown that much higher degradation efficiency of phenol is achieved on rGO/TiO\({}_{2}\) photoelectrode than that by photocatalytic (PC) and electrocatalytic (EC) processes, suggesting that photoelectric synergy effect is obtained over rGO/TiO\({}_{2}\) photoelectrode [43].  
Figure 8: Scheme for the fabrication of rGO/TiO\({}_{2}\) photoelectrode. Reprinted with permission from [43]. Copyright 2020 Elsevier.  
Figure 7: SEM images of as-synthesized samples: (**a**) BiVO\({}_{4}\) with smooth surface; (**b**) rGO/BiVO\({}_{4}\) with rGO layer uniformly attached on BiVO\({}_{4}\) forming a wrinkled surface, and (**c,d**) TEM images of rGO/BiVO\({}_{4}\) exhibiting a tight contact between BiVO\({}_{4}\) and the rGO layer (about 2 nm). Reprinted with permission from [42]. Copyright (2014) ACS.  
[PERSON] et al. have employed the hydrothermal method to synthesize titania nanowires (NW), and then fabricate G/TiO\({}_{2}\) nanowire nanocomposite (GNW) [44]. The reference samples, i.e., graphene-titania nanoparticles (NP) and nanocomposite (GNP), have also been prepared for comparative study on the resultant properties and photocatalytic performance of obtained photocatalysts. It has been found that by graphene incorporation, GNP and GNW have better performance than their counterparts. Additionally, uniform dispersion of titania on graphene is critical for the photocatalytic effect of the composite (Figure 9). More importantly, it has been shown that NWs, in comparison with NPs, have more uniform dispersion on graphene with less agglomeration, resulting in better direct contact between titania and graphene, and hence further improvement in charge carriers' separation and transportation. The adsorption ability of GNW is also higher than that of GNP. It has been found that the relative photocatalytic activity of GNW is much higher than that of GNP, and pure NWs and NPs photocatalysts.  
Another morphological form of titania has been used by [PERSON] et al., i.e., mesoporous titania (m-TiO\({}_{2}\)) as a shell of sandwich-structured r-GO/AuNP/m-TiO\({}_{2}\) hollow hybrids [45]. The photocatalyst, prepared by the combination of sol-gel and self-assembly methods (Figure 10), exhibits large surface area and superior adsorption ability. It has been proposed that high photocatalytic performance is attributed to the porous nature of the hybrid shells, enhanced charge separation and visible-light absorption by r-GO and AuNPs, and thus indicating that the introduction of r-GO and AuNPs improves the photocatalytic activity of titania.