Synthesis of novel MgAl layered double oxide grafted TiO2 cuboids and their photocatalytic activity on CO2 reduction with water vapor

Abstract

A series of magnesium/aluminum (MgAl) layered double oxide (LDO) grafted TiO₂ cuboids (MgAl-LDO/TiO₂) with various molar ratios of (Mg + Al) to Ti were synthesized by a combination of hydrothermal and coprecipitation methods, in which the growth of MgAl-LDO platelets was controlled. The MgAl-LDO/TiO₂ composite materials were used for photocatalytic CO₂ reduction with water vapor under UV light irradiation in a continuous-flow reactor. CO was found to be the main product from CO₂. At near room temperature (e.g., 50 °C), MgAl-LDO/TiO₂ did not significantly enhance CO₂ reduction compared with pure TiO₂ cuboids. At a moderately elevated reaction temperature (e.g., 150 °C), the MgAl-LDO/TiO₂ sample with an optimum 10 wt.% MgAl-LDO loading demonstrated CO₂ reduction activity five times higher than that of bare TiO₂ cuboids. The photo-induced electrons on TiO₂ may migrate to the MgAl-LDO/TiO₂ interfacial sites to promote CO₂ reduction. Findings in this work may lead to a new area of hybrid adsorbent/photocatalyst materials that are capable of sequential CO₂ capture and photocatalytic conversion.