A Facile Method To Prepare Novel Ag2O/Ag2CO3 Three-Dimensional Hollow Hierarchical Structures and Their Water Purification Function

A facile, green, and low-cost method to prepare novel Ag2O/Ag2CO3 three-dimensional hollow flowerlike hierarchical microspheres has been demonstrated. The microspheres were obtained by simple injection of Na2CO3 aqueous solution into AgNO3 ethanol solution. The surface morphology of the microspheres was relatively smooth, trumpet flowerlike hole, and flowerlike shallow hole when the reaction temperature was 8, 25, and 70 °C, respectively. They were assembled by nanoparticles. The microsphere prepared at 25 °C was composed of 86.3% Ag2CO3 and 13.7% Ag2O. The HTEM image indicates that the Ag2CO3 microsphere is wrapped by a thin Ag2O layer, and there is a heterojunction between Ag2CO3 and Ag2O. The study of the formation mechanism demonstrates the first example of using water-soluble Na2CO3 as templates to prepare 3D hierarchical microstructures. The Ag2O/Ag2CO3 microspheres prepared at 25 °C have excellent adsorption and photocatalysis activity for Congo red (CR). The adsorption behavior of the Ag2O/Ag2CO3 microsphere follows the Langmuir isothermal adsorption model. The maximal adsorption capacity of the Ag2O/Ag2CO3 microsphere was about 100.84 mg g–1 for CR in water. Here, 87.5% of CR was removed within 20 min under visible light irradiation at an initial concentration of CR of 80 mg L–1 with a photodegradation rate constant, k, of 0.06814. The radicals (O2·–,·OH) and hole (h+) were proved to be the active species for photocatalyzing CR. The microspheres were reused five times without distinct loss of photocatalysis activity, which indicated that they have stable photocatalysis activity.