Synthesis and Optimization of Ti/Li/Al Ternary Layered Double Hydroxides for Efficient Photocatalytic Reduction of CO to CH.

A series of Ti/Li/Al ternary layered double hydroxides (TiLiAl-LDHs) with different Ti:Li:Al molar ratios were prepared by a coprecipitation method for photocatalytic CO reduction. It was demonstrated that the contents of anions between the layers of Ti/Li/Al-LDHs greatly determined the photocatalytic activity for CO reduction. With Ti:Li:Al molar ratios optimized to be 1:3:2, the largest contents of [Formula: see text] anion and hydroxyl group were obtained for the TiLiAl-LDHs sample, which exhibited the highest photocatalytic activity for CO reduction, with CH production rate achieving 1.33 mmol h g. Moreover, the theoretical calculations show that TiLiAl-LDHs is a p-type semiconductor with the narrowest band gap among all the obtained TiLiAl-LDHs. After calcined at high temperatures such as 700 °C, and the obtained TiLiAl-700 sample showed much increased photocatalytic activity for CO reduction, with CH production rate reaching about 1.59 mmol h g. This calcination induced photocatalytic enhancement should be related to the cystal structure transformation from hydrotalcite to mixed oxides containing high reactive oxygen species for more efficient CO reduction.