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

Abstract 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.