Nanostructure rod-like TiO₂-reduced graphene oxide composite aerogels for highly-efficient visible-light photocatalytic CO₂ reduction

In response to the worldwide over-standard carbon dioxide emission problem, this work synthesized a series of titanium dioxide/reduced graphene oxide composite aerogels (TiO₂-rGO) for photoconversion of CO₂ by a one-step hydrothermal and freeze-drying method. The prepared composite aerogel presents a high specific surface area of 287.3 m²/g and pore volume of 0.72 cm³/g, contributing to remarkable absorption capability of reactants and fast intraparticle molecular transfer. In the three-dimensional structure of rGO aerogel, TiO₂ with nano-rod shape (10–20 nm × 100–150 nm) is uniformly interspersed. Through applying the composite catalytic aerogel for the photocatalysis reaction, CO₂ was efficiently converted to MeOH, CH₄, and EtOH, etc. The total yield of carbon generated by G-25Ti (TiO₂-rGO with 25 mmol Ti⁴⁺) was found 15.7 times higher than that of the pure P25. The corresponding characteristic analysis demonstrated that the photocatalytic performance of TiO₂-rGO composite aerogel has been highly improved, originated from two folds: (1) the introduction of 3-D rGO to nano-rod shape TiO₂ promoted its light absorption efficiency, and more significantly (2) the specific chemical bonding sites and strong O˭C‒O‒Ti group between rGO and TiO₂ effectively mitigate the recombination of photogenerated electron–hole pairs. In this work, rod-like TiO₂-rGO composite aerogels prepared by using TiCl₄ as precursor for the first time have been found a new application in CO₂ reduction using visible sunlight.