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

Abstract

Photocatalytic reduction of CO2 into value-added fuels (e.g., CO and CH4) 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 CO2 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 TiOx species in the LDHs, while the latter two methods resulted in the formation of crystalline anatase TiO2 when appropriate treatment temperatures were applied but the specific surface area was decreased due to the thermal treatment. Compared with commercial TiO2-P25 nanoparticles, all MgAlTi-LDHs prepared in this work demonstrated two to four times higher catalytic activities in CO2 photoreduction to CO. Among the MgAlTi-LDHs, the CO2 photoreduction activity was affected by both the crystallinity of TiO2 and the specific surface area. Consequently, the material hydrothermally treated at 150–200°C demonstrated the highest CO production due to a well-balanced TiO2 crystallinity and specific surface area. Findings in this work contribute to the development of efficient photocatalysts for CO2 reduction and advance the understanding of the catalyst property-activity relationships.