Preparation, Properties And Application Of Porous Metal Oxide By Thermal Decomposition

Porous metal oxides have been extensively investigated owing to their great potential applications in catalysis, adsorption as well as energy conversion and storage, due to their extraordinary characteristics, such as high surface area, high pore volume, well-defined morphology and structural flexibility. There are many methods to obtain porous structures, in which thermal decomposition process with oxalate as precursor has attracted more and more concerns, owing to its advantages such as convenience, widely flexibility, and feasibility to controllable porous structures. Herein, high crystallinity precursor magnesium oxalate dihydrate and copper oxalate hydrate with specific morphologies were synthesized first via a simple room-temperature co-precipitation or facile hydrothermal route. Then, hierarchical porous MgO and porous CuO structures with well faceted profile and high crystallinity were successfully obtained by the subsequent thermal conversion of the corresponding oxalate precursor. Besides, hierarchical porous MgO and CuO were employed as adsorbents or photocatalyst for model waste water treatment to investigate the potential applications in the related fields.In the synthesis of hierarchical porous MgO, precursor MgC2O4·2H2O polyhedrons and microrods were obtained via a room-temperature co-precipitation and facile hydrothermal route thereafter, respectively, by using Na2C2O4and MgCl2·6H2O as the raw materials. The results showed that, the hydrothermal treatment of the polyhedrons brought about the elongated or1D preferential growth, leading to longer and even higher aspect ratio microrods. During the thermal conversion process, hierarchical porous MgO structures with high crystallinity, well-defined polyhedron-like and rod-like morphologies have been synthesized via a flux NaCl and surfactant NP-9assisted calcination of the corresponding oxalate precursor. The possible formation mechanisms were proposed, which indicated that the successive and synergistic effect of NaCl and NP-9gave rise to the final porous MgO structures whereas with well faceted profile of the precursor preserved. The as-obtained hierarchical porous MgO superstructures were very efficient and effective as the adsorbents for methylene blue and catalyst support for single-walled carbon nanotubes growth, while hierarchical porous MgO microrods exhibited excellent adsorption efficiency for removal of heavy metal ions including Pb (Ⅱ) and Cr (VI) from aqueous solutions, and the removal efficiency of Pb (Ⅱ)(50.0mg L-1) and Cr (VI)(1.0mg L-1) was up to99.5%and55.6%, respectively.Porous CuO microspheres were synthesized via a similar room-temperature coprecipitation followed by calcination process using CuCl2and Na2C2O4as raw materials. The as-obtained porous CuO microspheres showed well degradation abilities for Rhodamine B under UV light radiation, and the degradation rate was38.6%. All of the above work indicates that such porous structures could be employed as great potential candidates in dye containing water treatment as well as heterogeneous catalysis.