Diatomite interface-mediated MnO₂ growth for enhanced hydroxyl activity and mass transfer in efficient room-temperature formaldehyde degradation

Traditional indoor formaldehyde (HCHO) treatment technologies often rely on light or thermal fields to supply catalytic energy, limiting their practical application in indoor environments. This study presents an in-situ growth strategy for uniformly loading δ-MnO₂ onto diatomite to achieve efficient room-temperature catalytic oxidation of HCHO. The size of δ-MnO₂ on the δ-MnO₂/diatomite (50% MD) composite is significantly reduced, forming a microporous structure, with δ-MnO₂ nanoflowers uniformly dispersed on the diatomite surface. The optimal 50% MD composite exhibits a hierarchical pore structure, greatly enhancing catalytic site exposure, and achieving a HCHO removal rate of 98.0%. The enhanced performance is attributed to the interaction between diatomite and δ-MnO₂, which optimizes the particle size and dispersion of δ-MnO₂, increases the Mn³⁺ content, and improves the surface oxygen activity of δ-MnO₂. In-situ DRIFTS analysis demonstrates that 50% MD possesses the highest adsorption capacity of H₂O, which is conducive to accelerating the conversion of intermediates and promoting the desorption of CO₂. Moreover, SEM-FIB analysis intuitively reveals efficient H₂O mass transfer on 50% MD to aid hydroxyl groups (–OH) regeneration. This work establishes a cost-effective, energy-free, and scalable strategy for indoor HCHO purification via coupled mineral-enabled transport engineering and interface-driven MnO₂ activation.