Controllable Synthesis of Hierarchical Nanoporous Ɛ-MnO2 Crystals for the Highly Effective Oxidation Removal of Formaldehyde

Hierarchical nanoporous Ɛ-MnO2 crystals were prepared through thermal decomposition of the hydrothermally-synthesized MnCO3 precursors without any outside templates or surfactants. Through the reactant altering, cubes, nano-blocks aggregated microspheres and nanoparticle aggregated microspheres of Ɛ-MnO2 could be selectively generated. After preparation of Ɛ-MnO2, the filtrate containing triethylene glycol (TEG) and ethylene diamine (EDA) could be reused to synthesize precursor MnCO3. Since the thermal decomposition of precursor MnCO3 not only led to formation of hierarchical Ɛ-MnO2 structure but also increased the specific surface area, the catalytic performance of the formed Ɛ-MnO2 in the oxidation of formaldehyde (HCHO) was enhanced. The specific surface area of nanoparticles aggregated microspheres was 168.3 m2·g-1 in which HCHO conversion could remain at above 96 % during 72 h with 160 ppm of HCHO and 84,000 mL·g-1·h-1 of gas hourly space velocity.