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.