3D Yolk@Shell TiO_2–x/LDH Architecture: Tailored Structure for Visible Light CO₂ Conversion

CO2 photoconversion into hydrocarbon solar fuels by engineered semiconductors is considered as a feasible plan to address global energy requirements in times of global warming. In this regard, three-dimensional yolk@shell hydrogenated TiO2/Co–Al layered double hydroxide (3D Y@S TiO2–x/LDH) architecture was successfully assembled by sequential solvothermal, hydrogen treatment, and hydrothermal preparation steps. This architecture revealed a high efficiency for the photoreduction of CO2 to solar fuels, without a noble metal cocatalyst. The time-dependent experiment indicated that the production of CH3OH was almost selective until 2 h (up to 251 μmol/gcat. h), whereas CH4 was produced gradually by increasing the time of reaction to 12 h (up to 63 μmol/gcat. h). This significant efficiency can be ascribed to the engineering of 3D Y@S TiO2–x/LDH architecture with considerable CO2 sorption ability in mesoporous yolk@shell structure and LDH interlayer spaces. Also, oxygen vacancies in TiO2–x could provide excess sites for sorption, activation, and conversion of CO2. Furthermore, the generated Ti3+ ions in the Y@S TiO2 structure as well as connecting of structure with LDH plates can facilitate the charge separation and decrease the band gap of nanoarchitecture to the visible region.