Medium-Entropy LDH-Driven Electronic Coupling of MnOx for Preferential Oxidation of Formaldehyde

Preferential oxidation of formaldehyde (HCHO) in natural gas engine exhaust is pivotal to prevent NH3-SCR catalyst deactivation and inhibit highly toxic hydrogen cyanide (HCN) formation. Although manganese-based catalysts exhibit prominent activity for HCHO oxidation, complete mineralization is still hindered by poor electron-transfer efficiency and insufficient reactive oxygen species (ROS) generation. Herein, we fabricate hierarchical medium-entropy LDH nanoflower-anchored MnOx catalysts (MnO2@NiMgAl-MELH) via a facile in situ growth strategy, enabling 100% mineralization of HCHO at room temperature. Structural characterizations and DFT calculations verify that Ni-Mn electronic coupling optimizes the electronic structure, facilitates charge transfer, reduces oxygen vacancy formation energy, and boosts O2 and H2O activation to generate abundant ROS (O2-, O22-, and surface -OH). Furthermore, in situ DRIFTS confirms that ROS synergistically accelerate HCHO and formate intermediate oxidation, achieving complete mineralization of HCHO. This work develops a low-cost and high-performance catalyst for HCHO preferential oxidation and offers a broadly applicable strategy for air pollutant purification.