Method for preparing the nano-porous oxide-noble metal composite material by deoxidation

Abstract

The present invention discloses a method for preparing the nano-porous oxide-noble metal composite material by deoxidation, comprising dissolving the noble metal ion or fine particles, the oxide salt to be dissolved and the target oxide salt in the pure water in a proportion to form the mixed solution, adding the surface active agent, and stirring magnetically; dropping the precipitant gradually to form the precipitate, stirring for 4 h, separating and cleaning the precipitate, and drying, grinding and calcining at a high temperature; corroding fully and dissolving part of the oxide with an etchant, preserving the noble metal and the target oxide, separating, cleaning, drying at 80 C., and heat treating at a high temperature to obtain the nano-porous oxide-noble metal composite material. The present invention has the technological advantages of simple operation, low energy consumption, environmental protection and suitable for batching, etc.

Claims

1. A method for preparing a nano-porous oxide-noble metal composite material by deoxidation, comprising the steps of: S1: dissolving 0.1243-1.243 parts (weight component) of noble metal ions or particles, 3.9484-4.5559 parts (weight component) of an oxide salt to be dissolved, 2.8148-3.7835 parts (weight component) of a target oxide salt in 200 ml of ultrapure water to form a mixed solution, adding 0.2-0.25 parts (weight component) of a surfactant, and stirring for 5 to 10 minutes; S2: forming a precipitate by adding a precipitant into the mixed solution until the precipitate is not increasing, stirring for about 4 hours, centrifuging and cleaning the precipitate, drying the precipitate at 80-85 C., grounding, and calcining at a temperature of between 500 C. and 800 C. to form an oxide complex containing noble metal; S3: etching the oxide complex with an etchant to dissolve a part of the oxides and to preserve the noble metal and the target metal oxide, separating, cleaning, drying at 80-85 C. to form a dried power, heat treating at about 400 C. the oxide complex, to obtain a nano-porous oxide noble metal composite material.

2. The method according to claim 1, wherein the noble metal is silver, gold, platinum or palladium.

3. The method according to claim 1, wherein the target oxide is cerium oxide, zirconium oxide, titanium oxide, or lanthanum oxide.

4. The method according to claim 1, wherein the oxide salt to be dissolved is a salt of copper oxide, aluminum oxide, or iron oxide and the like.

5. The method according to claim 1, wherein the surfactant is 2 wt % PVP.

6. The method according to claim 1, wherein the etchant is selected from the group consisting of dilute hydrochloric acid and dilute sulfuric acid, at a mass concentration of 5-6 wt %.

7. The method according to claim 1, wherein S3 further comprises using an XRD analysis phase, and if the noble metal participates in the reaction during the etching process, reducing the noble metal.

8. The method according to claim 7, wherein reducing the noble metal comprises: dispersing the dried powder in a 2 wt % sodium hydroxide solution, gradually adding 5 wt % of a glucose solution to an excess, reacting for 4 hours, reducing the noble metal involved in the reaction to produce a simple substance of noble metal, and then proceeding with cleaning, drying and heat treating at 400 C.

Description

DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is XRD spectrums of the complex of CeO.sub.2/CuO/Ag before corrosion (a) and after corrosion (b).

(2) FIG. 2 is a electron photographs of the scanning (a, b) and transillumination (c, d) of the nano-porous CeO.sub.2Ag (5%) composite material prepared according to example 1 of the present invention.

(3) FIG. 3 shows the catalytic oxidation of CO in performance of nano-porous CeO.sub.2Ag composite material with different silver contents.

(4) FIG. 4 shows the catalytic oxidation of CO in stable performance of nano-porous CeO.sub.2Ag (10%) composite material with different silver contents for 60 hours.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(5) The present invention will now be described in further detail with reference to the specific embodiments:

Example 1: Preparing for Nano-Porous CeO2Ag (5 wt. %) Composite Material

(6) 0.1243 g of silver nitrate, 4.5559 g of copper nitrate and 3.7835 g of cerium nitrate were dissolved in 200 ml of ultrapure water to form a mixed solution, and into which 0.2 g of PVP was added, followed by stirring magnetically for 10 minutes. 3 g of sodium hydroxide was dissolved in 50 ml of ultra-pure water to produce a precipitant, which gradually was dropped in the mixed solution, forming the precipitation rapidly, and continued to stir for 4 h. After the precipitate was centrifuged and washed, it was dried at 80 C. for 12 h. And then the dried precipitate was calcined at 500 C. for 2 h in the air atmosphere to obtain the complex of Ag/CuO/CeO.sub.2 The complex was sufficiently etched in 5 wt % dilute hydrochloric acid, and the solution gradually became blue. After separating and washing it, the solution was dried at 80 C. (the XRD indicates that the nano-porous cerium oxide-silver chloride complex was formed). The powder was dispersed in the 2 wt % sodium hydroxide solution, and a 5 wt % dextrose solution was added dropwise to cause an excess. After reacting for 4 h, washing, drying and heat treating the powder at 400 C. produced the nano-porous CeO.sub.2Ag (5 wt %) composite material.

Example 2: Preparing for Nano-Porous CeO2Ag (30 wt. %) Composite Material

(7) 0.8772 g of silver nitrate, 3.9484 g of copper nitrate and 3.2791 g of cerium nitrate were dissolved in 200 ml of ultrapure water to form a mixed solution, and into which 0.21 g of PVP was added, followed by stirring magnetically for 10 minutes. 3 g of sodium hydroxide was dissolved in 50 ml of ultra-pure water to produce a precipitant, which gradually was dropped in the mixed solution, forming the precipitation rapidly, and continued to stir for 4 h. After the precipitate was centrifuged and washed, it was dried at 82 C. for 12 h. And then the dried precipitate was calcined at 500 C. for 2 h in the air atmosphere to obtain the complex of Ag/CuO/CeO.sub.2 The complex was sufficiently etched in 5.8 wt % dilute hydrochloric acid, and the solution gradually became blue. After separating and washing it, the solution was dried at 82 C. The powder was dispersed in a 2 wt % sodium hydroxide solution, and a 5 wt % dextrose solution was added dropwise to cause an excess. After reacting for 4 h, washing, drying and heat treating the powder at 400 C. produced the nano-porous CeO.sub.2Ag (30 wt %) composite material.

Example 3: Preparing for Nano-Porous CeO2Ag (10 wt. %) Composite Material

(8) 0.2953 g of silver nitrate, 4.559 g of copper nitrate and 3.7835 g of cerium nitrate were dissolved in 200 ml of ultrapure water to form a mixed solution, and into which 0.24 g of PVP was added, followed by stirring magnetically for 10 minutes. 3 g of sodium hydroxide was dissolved in 50 ml of ultra-pure water to produce a precipitant, which gradually was dropped in the mixed solution, forming the precipitation rapidly, and continued to stir for 4 h. After the precipitate was centrifuged and washed, it was dried at 85 C. for 12 h. And then the dried precipitate was calcined at 500 C. for 2 h in the air atmosphere to obtain the complex of Ag/CuO/CeO.sub.2 The complex was sufficiently etched in 5.5 wt % dilute hydrochloric acid, and the solution gradually became blue. After separating and washing it, the solution was dried at 85 C. The powder was dispersed in a 2 wt % sodium hydroxide solution, and a 5 wt % dextrose solution was added dropwise to cause an excess. After reacting for 4 h, washing, drying and heat treating the poder at 400 C. produced the nano-porous CeO.sub.2Ag (10 wt %) composite material.

Example 4: Preparing for Nano-Porous ZrO2Ag (30 wt. %) Composite Material

(9) 1.0124 g of silver nitrate, 4.559 g of copper nitrate and 2.8148 g of zirconium nitrate were dissolved in 200 ml of ultrapure water to form a mixed solution, and into which 0.25 g of PVP was added, followed by stirring magnetically for 10 minutes. 3 g of sodium hydroxide was dissolved in 50 ml of ultra-pure water to produce a precipitant, which gradually was dropped in the mixed solution, forming the precipitation rapidly, and continued to stir for 4 h. After the precipitate was centrifuged and washed, it was dried at 85 C. for 12 h. And then the dried precipitate was calcined at 500 C. for 2 h in the air atmosphere to obtain the complex of Ag/CuO/ZrO.sub.2. The complex was sufficiently etched in 6 wt % dilute hydrochloric acid, and the solution gradually became blue. After separating and washing it, the solution was dried at 80 C. The powder was dispersed in a 2 wt % sodium hydroxide solution, and a 5 wt % dextrose solution was added dropwise to cause an excess. After reacting for 4 h, washing, drying and heat treating the powder at 400 C. produced the nano-porous CeO.sub.2Zr (30 wt %) composite material.

Example 5: Preparing for Nano-Porous CeO2Au (3 wt. %) Composite Material

(10) 0.1243 g of silver nitrate, 4.5559 g of copper nitrate and 3.7835 g of cerium nitrate weredissolved in 200 ml of ultrapure water to form a mixed solution, and into which 0.21 g of PVP was added, followed by stirring magnetically for 10 minutes. 3 g of sodium hydroxide was dissolved in 50 ml of ultra-pure water to produce a precipitant, which gradually was dropped in the mixed solution, forming the precipitation rapidly, and continued to stir for 4 h. After the precipitate was centrifuged and washed, it was dried at 85 C. for 12 h. And then the dried precipitate was calcined at 500 C. for 2 h in the air atmosphere to obtain the complex of Ag/CuO/CeO.sub.2 The complex was sufficiently etched in 5.2 wt % dilute hydrochloric acid, and the solution gradually became blue. After separating and washing it, the solution was dried at 83 C. (the XRD indicates that the porous cerium oxide-silver chloride complex is formed). The powder was dispersed in a 2 wt % sodium hydroxide solution, and a 5 wt % dextrose solution was added dropwise to cause an excess. After reacting for 4 h, washing, drying and heat treating the powder at 400 C. produced the nano-porous CeO.sub.2Ag (5 wt %) composite material. The composite powder was reacted with 0.1% by weight of chloroauric acid and the silver chloride was washed with ammonia to obtain nanoporous CeO2-Au (3 wt. %) Composite.

Example 6: Preparing for Nano-Porous ZrO2Au (18 wt. %) Composite Material

(11) 1.0124 g of silver nitrate, 4.5559 g of copper nitrate and 2.8148 g of zirconium nitrate were dissolved in 200 ml of ultrapure water to form a mixed solution, and into which 0.25 g of PVP was added, followed by stirring magnetically for 10 minutes. 3 g of sodium hydroxide was dissolved in 50 ml of ultra-pure water to produce a precipitant, and which gradually was dropped in the mixed solution, forming the precipitation rapidly, and continued to stir for 4 h. After the precipitate was centrifuged and washed, it was dried at 85 C. for 12 h. And then the dried precipitate was calcined at 500 C. for 2 h in the air atmosphere to obtain the complex of Ag/CuO/ZrO.sub.2 The complex was sufficiently etched in 5.5 wt % dilute hydrochloric acid, and the solution gradually became blue. After separating and washing it, the solution was dried at 85 C. The powder was dispersed in a 2 wt % sodium hydroxide solution, and a 5 wt % dextrose solution was added dropwise to cause an excess. After reacting for 4 h, washing, drying and heat treating the powder at 400 C. produced the nano-porous ZrO.sub.2Ag (30 wt %) composite material. The composite powder was reacted with 0.1% by weight of chloroauric acid and the silver chloride was washed with ammonia to obtain nanoporous ZrO.sub.2Au (18 wt. %) Composite.

(12) The XRD spectrums of the complex of CeO.sub.2/CuO/Ag before corrosion (a) and after corrosion (b) are shown in FIG. 1. As can be seen from FIG. 1, the phase structure is CuOCeO.sub.2Ag complex before corrosion, and mainly containing CeO.sub.2 and Ag after corrosion, indicating that the CeO.sub.2 based composite material obtained.

(13) The electron photographs of the scanning (a, b) and transillumination (c, d) of the nano-porous CeO.sub.2Ag (5%) composite material prepared according to example 2 are shown in FIG. 2, wherein 2a and 2b are photographs of different magnification. It can be seen that the material is a homogeneous porous structure and the pore walls are nanoparticles. It can be seen more clearly from the transmitted photographs of FIGS. 2c and 2d that it is the micrographs. Where CeO.sub.2 is interconnected to construct a porous structure with 10 nm, the microparticles are of about 10 nm. Wherein the Ag nanoparticles are embedded in the porous structure and have a size of about 60 nm.

(14) FIG. 3 shows the catalytic oxidation of CO in performance of nano-porous CeO.sub.2Ag composite material prepared in examples 1, 2 and 3, and from which it can be seen that the catalytic effect is enhanced with the increasing of Ag content, in which the catalytic effect of CeO.sub.2Ag (10 wt. %) is better, and the temperature of 50% conversion is 131 degrees Celsius. But with the further increase in silver content, low temperature catalytic effect is poor, and the high temperature catalytic effect is not different significantly.

(15) FIG. 4 shows the catalytic oxidation of CO in stable performance of nano-porous CeO.sub.2Ag (10%) composite material with different silver contents for 60 hours. It can be seen from FIG. 4 that the CeO.sub.2Ag (10 wt. %) material has no attenuation at 300 C. after 65 hours, indicating that the oxide-based noble metal composite material prepared by this method has a good stability.

(16) While many embodiments of the present invention have been described, it is to be understood that within the scope and spirit of the present invention, other embodiments of the invention and/or variations, combinations and substitutions of the present invention may be made are obvious to one of ordinary skills in the art.