Construction of oxygen-rich vacancies and heterojunctions coupled with different morphologies of CeO2/mesoporous TiO2 framework structures for efficient photocatalytic CO2 reduction performance

Abstract

The coupling of efficient adsorption and effective charge separation with photocatalysts enables the use of sunlight for photocatalytic reduction of carbon dioxide (CO₂) into high-value-added products. In this work, we used a straightforward solid-phase hydrothermal technique to build an oxygen-vacancy-rich, heterogeneous interface-coupled CeO₂/mesoporous TiO₂ framework structural system. The heterogeneous structure was constructed by introducing oxygen-vacancy-rich CeO₂ into mesoporous TiO₂, which may encourage the transfer of charges and increase the number of active sites and CO₂ adsorption by utilizing the coupled synergistic effect of oxygen vacancies and heterogeneous interfaces, and it can also regulate the pathway of the photocatalytic reaction and the selectivity of the products. The composite of CeO₂ with different morphologies and oxygen-rich vacancies regulated the system's active sites and degree of exposure and enhanced photocatalytic CO₂ reduction. The highest CO yield of 6.25 mmol g_cat⁻¹ was obtained by use of the rod CeO₂/mesoporous TiO₂ composite photocatalyst (R-CeO₂/TiO₂), and this yield was 1.6 times higher than that of pure mesoporous TiO₂ and 1.84 times higher than that of pure R-CeO₂. Also, the product selectivity increased by 4.3% compared to a single sample. Combining the Mott–Schottky plot results and the energy-barrier perspective to further explore the photocatalytic reduction of the CO₂ reaction mechanism as well as the product selectivity, it appears that the construction of the composite system of oxygen-rich vacancies and heterogeneous boundary-coupled photocatalysis provides a practical pathway for the photocatalytic reaction, which may contribute to the photocatalytic reaction's high efficiency and yield selectivity.