Preparation and immobilisation of Brookite-type Ti3+-TiO2 for photocatalytic ammonia synthesis from N2 and H2O

Abstract

In this work, a Ti3+-doped brookite-type TiO2 crystal (Ti3+–TiO2) was prepared using a NaBH4 thermal reduction method. A composite photocatalyst Ti3+–TiO2/C was obtained on a glass plate by heat treatment to remove organic substances. The structure of the as-prepared photocatalyst was characterised, and the immobilisation conditions were optimised. Furthermore, photocatalytic ammonia synthesis from N2/H2O was investigated. The results show that the introduction of the carbon carrier not only can enhance the ability of Ti3+–TiO2/C to transport photogenerated electrons but also can prevent the recombination of photogenerated electrons and holes through the transfer of electrons by the carbon substrate. Meanwhile, the oxygen-containing groups linked to the carbon carrier can improve the N2 adsorption and activation ability of the photocatalyst, which improved the photocatalytic ammonia synthesis activity of Ti3+–TiO2/C. The ammonia yield on the Ti3+–TiO2/C composite photocatalyst reached 0.313 µmol/(L·cm2) after 4 h of photocatalytic ammonia synthesis reaction from N2/H2O, which is 2.51 times higher than that on pure Ti3+–TiO2 under the same conditions. In addition, in this work, we used immobilised Ti3+–TiO2/C as a photocatalyst, which simplifies the method of recycling the catalyst and provides an idea for the industrialisation of the photocatalytic reaction.