Synthesis and Optimization of Ti/Li/Al Ternary Layered Double Hydroxides for Efficient Photocatalytic Reduction of CO(2) to CH(4)

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(2) reduction. It was demonstrated that the contents of anions between the layers of Ti/Li/Al-LDHs greatly determined the photocatalytic activity for CO(2) 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 Ti(1)Li(3)Al(2)-LDHs sample, which exhibited the highest photocatalytic activity for CO(2) reduction, with CH(4) production rate achieving 1.33 mmol h(−1) g(−1). Moreover, the theoretical calculations show that Ti(1)Li(3)Al(2)-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(2) reduction, with CH(4) production rate reaching about 1.59 mmol h(−1) g(−1). 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(2) reduction.