Silver phosphate (Ag3PO4) is one of the ideal candidate materials in the field of photocatalysis due to its low toxicity, wide photoresponse range, and good photocatalytic performance, and has attracted wide attention from people from all walks of life. So far, researchers have prepared Ag3PO4 through various methods, which will provide technical support for the development and utilization of Ag3PO4, and other Ag-based or PO4-based photocatalysts can also learn from its preparation methods.
Preparation Methods
1. Solid phase grinding method
The solid phase grinding method uses grinding technology to realize the preparation of photocatalytic materials through ion exchange between reactants at room temperature. Using solid AgNO3 and Na2HPO4 or Na3PO4 as raw materials, irregular Ag3PO4 particles are prepared by grinding at room temperature with a size of about 0.5~2.0 µm. Usually, the morphology of materials prepared by this method is uncontrollable.
2. Aqueous precipitation method
Aqueous phase precipitation is usually a method of precipitation from solution by the formation of insoluble metal salts or metal hydrated oxides in the aqueous phase by a metal salt solution and precipitant. However, the product prepared by the aqueous precipitation method depends on the system environment and nucleation rate; the reaction speed is fast, and the crystal growth process cannot be controlled, so the morphology of the precipitated product cannot be controlled.
By adding some auxiliaries to form different reaction precursors, the nucleation rate and growth rate of the crystal can be controlled, and some Ag3PO4 products with controllable morphology can be obtained. For example, adding NH3·H2O to AgNO3 solution to form silver ammonia solution ([Ag(NH3)2]NO3) solution, and then adding Na2HPO4 solution to the system to form hierarchical cubic Ag3PO4 microcrystals.
3. Organic phase precipitation method
Due to the different existing states of reactants in the organic phase and aqueous phase, materials with special morphology can be prepared by the organic phase precipitation method. Tetrahedral Ag3PO4 crystals exposed to highly active {111} faces were prepared by using AgNO3 ethanol solution and H3PO4 ethanol solution.
4. Organic/aqueous precipitation method
Taking advantage of the special existing state of the reactants in the organic/water mixed phase and controlling the reaction kinetics, some precipitated products exposing specific crystal planes and morphologies can also be prepared. Dendritic, tetragonal, nanorod, and triangular Ag3PO4 products were obtained after adding H3PO4 to the static and ultrasonic dimethylformamide/water mixed solution (DMF/H2O (1:1)) at different time. It was found that the reaction conditions, reaction time, and the ratio of mixed solvents had a great influence on the morphology and properties of the products.
5. Liquid-solid oxidation and ion exchange method
Using Ag, H2O2, and NaH2PO4 as raw materials, Ag3PO4 products can also be prepared by liquid-solid oxidation and ion exchange, which is a new idea for the preparation of Ag3PO4. Two-dimensional dendritic Ag3PO4 products were prepared by Ag nanowires, polyvinylpyrrolidone (PVP), NaH2PO4, and H2O2.
6. Hydrothermal method
The hydrothermal method refers to a chemical reaction carried out in a specially designed sealed pressure vessel, using an aqueous solution as the reaction system, under high temperature and pressure conditions, to dissolve and recrystallize commonly insoluble or insoluble substances. It is an effective method for preparing inorganic materials. The material prepared by this method has high purity, good grain development, and few structural defects. A highly active Ag3PO4 product with exposed {110} crystal planes was prepared by hydrothermal reaction using AgNO3 and H3PO4 as raw materials and urea hydrolysis to adjust the pH value of the system.
References
- Yi, Z.; et al. An orthophosphate semiconductor with photooxidation properties under visible-light irradiation. Nature materials 9.7 (2010): 559-564.
- Kumar, S.; et al. Template-free and eco-friendly synthesis of hierarchical Ag3PO4 microcrystals with sharp corners and edges for enhanced photocatalytic activity under visible light. Materials Letters 123 (2014): 172-175.
- Martin, D. J.; et al. Facet engineered Ag3PO4 for efficient water photooxidation. Energy & Environmental Science 6.11 (2013): 3380-3386.
- Dong, P.; et al. Shape-controllable synthesis and morphology-dependent photocatalytic properties of Ag3PO4 crystals. Journal of Materials Chemistry A 1.15 (2013): 4651-4656.
- Bi, Y.; et al. Two-dimensional dendritic Ag3PO4 nanostructures and their photocatalytic properties. Physical Chemistry Chemical Physics 14.42 (2012): 14486-14488.
- Wang, .; et al. Facile synthesis of novel Ag 3 PO 4 tetrapods and the {110} facets-dominated photocatalytic activity. CrystEngComm 15.1 (2013): 39-42.
