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-MnO 2 onto diatomite to achieve efficient room-temperature catalytic oxidation of HCHO. The size of δ-MnO 2 on the δ-MnO 2 /diatomite (50%MD) composite is significantly reduced, forming a microporous structure, with δ-MnO 2 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-MnO 2 , which optimizes the particle size and dispersion of δ-MnO 2 , increases the Mn 3+ content, and improves the surface oxygen activity of δ-MnO 2 . In-situ DRIFTS analysis demonstrates that 50%MD possesses the highest adsorption capacity of H 2 O, which is conducive to accelerating the conversion of intermediates and promoting the desorption of CO 2 . Moreover, SEM-FIB analysis intuitively reveals efficient H 2 O 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 MnO 2 activation. • In-situ growth of δ-MnO 2 on diatomite was successfully achieved. • Diatomite improves dispersion and reduces particle size of δ-MnO 2 . • Composite shows superior mass transfer of HCHO/H 2 O compared to bare δ-MnO 2 . • •Higher Mn 3+ content and active oxygen species promote HCHO oxidation. • •H 2 O adsorption boosts the conversion of intermediate products.