[Background andOverview][1]
In order to maximize the utilization of sunlight, people expect to develop more efficient visible light-responsive photocatalysts. In response to this problem, Professor Ye Jinhua from the Photocatalyst Materials Center of the Japan Physical Cosmetic Raw Materials and Materials Research Institute focused on the unexplored silver phosphate (Ag3PO4). According to the investigation Experimental results such as its water decomposition performance and paint decomposition performance under visible light irradiation revealed that the photooxidation performance of silver phosphate under visible light is dozens of times that of currently known photocatalysts. The relevant results were published in the materials edition of Nature magazine in an article titled “Phosphate semiconductors with photooxidation properties under visible light excitation”, which reported this new type of photocatalyst for the first time. The research center found that Ag3PO4 can absorb sunlight with a wavelength less than 520 nm, with a quantum yield of up to 90% under visible light, and exhibits excellent performance under visible light irradiation. Has strong oxidizing ability.
Silver PhosphateThe application of photocatalysts is far from limited to the degradation and removal of harmful substances. Its application in a wider range of fields is also possible, including applications in photovoltaics Systematic thin film electrode materials. Although silver phosphate cannot reduce water into hydrogen, it may be possible to split water to produce hydrogen by combining it with appropriate reducing materials.
[Physical and chemical properties][2]
English name: SILVER PHOSPHATE; CAS number: 7784-09-0; Molecular formula: Ag3 Mitsubishi Chemical ResinO4P; Molecular weight: 418.57600 Accurate mass: 415.66900 ; PSA: 96.06000; LogP: 0.38600; Density: relative density 6.37 (25℃) Melting point: 849℃; Properties: yellow cubic crystal. Chemical properties: Soluble in acid, potassium cyanide solution and ammonia water, slightly soluble in water and dilute acetic acid. Dissolution: Soluble in acid, potassium cyanide solution and ammonia water, slightly soluble in water.
[Purpose]
Used as photographic emulsion, catalyst, pharmaceutical and glass industries. Used to make silver bromide and silver iodide emulsions instead of silver nitrate emulsions. Used in place of silver nitrate emulsions. Preparation or Source: It can be prepared by the action of silver nitrate and sodium phosphate. Note: Turns brown when heated or exposed to sunlight.
Category: Inorganic salt; Production method: Add disodium hydrogen phosphate dodecahydrate aqueous solution dropwise to the silver nitrate solution to obtain silver phosphate precipitate, filter it, dissolve it in concentrated ammonia water, and slowly evaporate on a 60°C hot bath Silver phosphate crystals were obtained.
[Preparation method][1][3]
The synthesis methods of Ag3PO4 in the literature are almost all through Ag NO3 and Na3 To achieve the solid phase reaction of sub>PO4. Generally speaking, the product particles obtained by solid-phase reaction have large radius dispersion and irregular morphology. Compared with the traditional solid-phase reaction method, the liquid-phase precipitation method is easy to operate and controllable. At the same time, it can avoid the introduction of harmful impurities that are detrimental to the material. The generated product has higher chemical uniformity, finer particle size, and particle size distribution. Narrow and shaped.
The reaction between Ag NO3 and Na3PO4 is an ion exchange precipitation reaction, and the reaction speed is fast. Therefore, the reaction must be controlled well. Rate is a key factor in controlling particle size.
1. Preparation of silver phosphate cubic crystals by silver ammonia-assisted method
The chemical reagents used in the experiment are: silver nitrate (Ag NO3), sodium phosphate (Na3PO4·10H 2O), ammonia (NH3·H2O, 10%), deionized water (H2O), ethanol (CH3CH2OH), ethylene glycol ((HOCH2)2).
First prepare a silver ammonia solution, dissolve 3 mmol of silver nitrate into 90 ml of deionized water, and then add dilute ammonia to the above solution drop by drop at a rate of one drop per second, stirring while adding, until the initial formation of When the brown precipitate is completely dissolved, stop adding ammonia. Then add the previously prepared Na3PO4 (1 mmol) solution dropwise to the above solution, and react for 5 min under vigorous stirring. The samples were separated by centrifugation and washed three times with deionized water and absolute ethanol. All the above processes are carried out at room temperature. Finally, the samples were dried in a vacuum drying oven (80 °C), and the samples were taken out after drying for 10 hours.
Figure Illustration of the preparation of silver phosphate cubic crystals
The reaction process can be represented by the following two reaction equations:
2. Ion exchange method
The preparation of this experimental sample is achieved through a simple ion exchange method. Mix an appropriate amount of Na2HPO4 and AgNO3 solid powders, and grind them in an agate mortar to react until the color turns yellow. The chemical equation of the reaction is:
Rinse the mixture with distilled water and dry it to obtain pure yellow solid powder. The obtained Ag3PO4 is dispersed in the methylene blue solution and illuminated with a 450W gas lamp. After light-induced reduction for an appropriate time, the silver ions in Ag3PO4 are reduced to silver:
The generated Ag elemental precipitationaccumulate on the surface to form Ag/Ag3PO4 photocatalyst.
3. Preparation of silver phosphate by oleic acid-assisted method
Chemical reagents used in the experiment: silver nitrate (Ag NO3), sodium phosphate (Na3PO4·10H2O), sodium oleate (C18H33NaO2), deionized water (H2O), ethylene glycol ((HOCH2)2), octadecene (C18H36).
Figure Process of preparing silver phosphate by oleic acid-assisted method
First, disperse silver nitrate (3 mmol), sodium oleate (3 mmol) and sodium phosphate (1 mmol) into a certain volume of water. Then add sodium oleate dropwise to the aqueous solution containing silver nitrate, and react with vigorous stirring for a certain period of time to generate a silver-oleic acid complex. When the reaction is complete, add sodium phosphate dropwise to the upper solution. After 10 minutes of reaction, centrifuge the sample and wash it three times with deionized water and absolute ethanol. Finally, the samples were dried in a vacuum drying oven (80 °C), and the samples were taken out after drying for 10 hours.
[Prospects and future applications of silver phosphate][3]
(1) The organic matter introduced during the preparation process of silver phosphate nanoparticles cannot be completely removed, thus limiting the photocatalytic performance of silver phosphate nanoparticles. More excellent preparation methods need to be further explored.
(2) Since the raw materials required for the preparation of silver phosphate do not have a price advantage, it is of great significance to explore simple preparation methods to obtain high-efficiency silver phosphate catalysts for its industrial promotion.
(3) One of the goals of photocatalysis research is to use sunlight to achieve efficient photocatalysis. How to further improve the photoresponse wavelength of silver phosphate is also a very meaningful topic.
(4) Although the activity of the photocatalyst is very high, its instability under light will be a key issue restricting its application. New methods will continue to be explored and developed to further improve the stability of the catalyst. As a new type of photocatalyst, the research on its photocatalytic activity and mechanism is not in-depth enough. Conducting research in this area will provide a theoretical basis for its application and development. Expand the application scope of catalysts and explore their applications in photoelectric conversion, sterilization, and decomposition of toxic gases.
[References]
[1]Huang Lijun. Preparation of silver phosphate and research on its photocatalytic properties[D]. Jilin University, 2012.
[2]Chemical Dictionary
[3] Liu Yongping. Preparation and performance study of silver phosphate and its heterojunction efficient visible light catalyst[D]. Guangxi University, 2012.
