The sol was subjected to solvothermal treatment at 150 ◦C for 24 h, with a heating rate of
1 ◦C min−1. The resulting dark hydrogel was slowly dehydrated at
45 ◦C for 24 h, 60 ◦C for 12 h, and 80 ◦C for 12 h until a complete gel
particulate was formed. After thermal treatment at 100 ◦C for 24 h,
the obtained powder was extracted using boiling EtOH for 24 h to
remove the P123. The product was denoted as graphene/TiO2-x%,
where x represents the graphene loading in the composite. Pure
TiO2 and graphene/TiO2-0.91% (no P123) samples were also prepared
using the same method, but without graphene and P123,
respectively.