Layered Double Hydroxide Catalysts for Ozone Decomposition: The Synergic Role of M2+and M3+

In previous work, we successfully prepared a NiFe-layered double hydroxide (LDH) with superior activity and stability for catalytic ozone decomposition, which fundamentally avoids deactivation under high-humidity conditions. However, the role of the metal elements (M2+ and M3+) in LDH catalysts is not clear. Here, LDH materials containing different metals (NiFe, NiAl, NiMn, CoFe, and MgFe) were prepared by a simple co-precipitation method. It was found that the LDHs containing Ni2+ exhibited catalytic performance far superior to that of Co2+ and Mg2+ for ozone elimination, and NiFe-LDH had the best activity and stability among LDH materials prepared in this study. The NiFe-LDH can maintain 78% catalytic activity within 144 h at room temperature, even under a relative humidity of 65% and a space velocity of 840 L·g-1·h-1. Physicochemical characterizations demonstrated that chemical stability in an oxidizing atmosphere and the synergic role of M2+ and M3+ ions are crucial. The result of density functional theory calculation showed that the synergic role of Ni2+ and Fe3+ weakens the interaction between O and H in the O-H bond, which effectively lowers the reaction barrier of ozone decomposition compared with MgFe-LDH.