NiFe ₂ O ₄ -Triggered Hydrogen Spillover Pathway over NiFe-Layered Double Hydroxide (LDH) for Robust Room-Temperature Ozone Decomposition under Humid Conditions

Active hydrogen (*H)-mediated catalytic decomposition over layered double hydroxides (LDHs) offers an attractive approach to ozone (O 3 ) elimination in humid environments. However, their catalytic performance still seriously suffers from the insufficient ability for direct H 2 O activation, which restricts the replenishment of consumed surface *H and causes a potential competitive effect. Herein, a NiFe 2 O 4 -engineered NiFe-LDH catalyst with separated reactive sites was developed for room-temperature O 3 removal, where NiFe 2 O 4 acts as a hydrogen pump for H generation, and NiFe-LDH for O 3 conversion. Results reveal that the NiFe 2 O 4 /NiFe-LDH composite catalyst exhibits significantly enhanced catalytic activity and durability, achieving 99% of O 3 decomposition under 70% relative humidity at 25 °C with a reaction rate of 1319 μmol·g –1 ·h –1, which is 4.6 times that of pure NiFe-LDH. Experimental and density functional theory calculations demonstrate that H is efficiently generated from adsorbed H 2 O on Fe sites of NiFe 2 O 4 and subsequently transfer to the surface of NiFe-LDH for replenishing the consumed *H sites. This configuration weakens competitive adsorption and preferentially triggers a cross-interface hydrogen spillover pathway, which enables highly efficient and robust O 3 decomposition under harsh conditions. This work provides a novel and promising hydrogen spillover strategy through spatially separated active sites for boosting the level of O 3 purification.