CO2 photoreduction with water vapor by Ti-embedded MgAl layered double hydroxides

Abstract Photocatalytic reduction of CO 2 into value-added fuels (e.g., CO and CH 4 ) is a promising approach of storing solar energy and mitigating greenhouse gas emissions simultaneously. In this work, a novel material of crystallized titanium-embedded magnesium-aluminum layered double hydroxides (MgAlTi-LDHs) is developed and tested for CO 2 photoreduction with water. Three different materials synthesis methods were explored: (1) coprecipitation, (2) coprecipitation + hydrothermal, and (3) coprecipitation + calcination + reconstruction. The coprecipitation method alone only produced amorphous TiO x species in the LDHs, while the latter two methods resulted in the formation of crystalline anatase TiO 2 when appropriate treatment temperatures were applied but the specific surface area was decreased due to the thermal treatment. Compared with commercial TiO 2 -P25 nanoparticles, all MgAlTi-LDHs prepared in this work demonstrated two to four times higher catalytic activities in CO 2 photoreduction to CO. Among the MgAlTi-LDHs, the CO 2 photoreduction activity was affected by both the crystallinity of TiO 2 and the specific surface area. Consequently, the material hydrothermally treated at 150–200 °C demonstrated the highest CO production due to a well-balanced TiO 2 crystallinity and specific surface area. Findings in this work contribute to the development of efficient photocatalysts for CO 2 reduction and advance the understanding of the catalyst property-activity relationships.