Mesoporous TiO₂ Comprising Small, Highly Crystalline Nanoparticles for Efficient CO₂ Reduction by H₂O

Abstract

The conversion of CO₂ into hydrocarbon fuels with H₂O using low-cost photocatalysts can offer a sustainable route to meet some of our energy needs, besides being able to contribute to the solutions of global warming. In this work, a series of highly crystalline mesoporous titanium dioxide (TiO₂) photocatalysts are synthesized via a simple template-free synthetic method. The synthesis involves preparation of titanium glycolate microspheres (TGMs), then hydrolysis of the TGMs in boiling water under ambient pressure, and finally calcination of the products in air. The hydrolysis step is found to play a crucial role in the formation of TiO₂ microspheres comprising a network of small anatase grains. The hydrolysis of the TGMs is also found to considerably inhibit the possible phase transformation of anatase to rutile during the subsequent high-temperature crystallization process. The resulting materials have good crystallinity and efficient charge carrier separation capabilities, as well as large specific surface areas, and thus large density of accessible catalytically active sites. These unique structural features enable these materials to exhibit high photocatalytic activities for the conversion of CO₂ with H₂O into hydrocarbon fuels (CH₄) and to show much better catalytic activities than that of the commercial photocatalyst Degussa P25 TiO₂