METHOD FOR PREPARING BISMUTH OXIDE NANOWIRE FILMS BY HEATING IN UPSIDE DOWN POSITION

Abstract

A method for preparing bismuth oxide nanowire films by heating in an upside down position includes: washing a substrate, and fixing the substrate to a substrate support in a magnetron sputtering system in a position where an electrically conductive surface of the substrate faces downwards; placing a bismuth target, which is adhered to a copper backing plate, on a sputtering head in the magnetron sputtering system; performing direct current magnetron sputtering to form a bismuth film on the electrically conductive surface of the substrate; and regulating a heating temperature to maintain the bismuth film in a semi-molten state, and providing a predetermined oxygen gas concentration to form the bismuth oxide nanowire film.

Claims

1. A method for preparing a bismuth oxide nanowire film by heating in an upside down position, wherein a chemical formula of bismuth oxide is Bi.sub.2O.sub.3, and the method comprises: washing a substrate, and fixing the substrate to a substrate support in a magnetron sputtering system in a position, wherein an electrically conductive surface of the substrate faces downwards in the position; placing a bismuth target on a sputtering head in the magnetron sputtering system, wherein the bismuth target is adhered to a copper backing plate; performing direct current magnetron sputtering to form a bismuth film on the electrically conductive surface of the substrate; and regulating a heating temperature to maintain the bismuth film in a semi-molten state, and providing a predetermined oxygen gas concentration to form the bismuth oxide nanowire film.

2. The method according to claim 1, comprising: (1) washing the substrate, and fixing the substrate to the substrate support in a sputtering chamber of the magnetron sputtering system in the position; placing the bismuth target on the sputtering head in the magnetron sputtering system, wherein the sputtering head is provided with a forced water cooling system, and the forced water cooling system is configured to maintain a temperature of the sputtering head at 10° C.-20° C.; closing a cover of the sputtering chamber; (2) vacuumizing the sputtering chamber, starting a rotation stage to rotate, heating the substrate to 25° C.-274° C., and starting the forced water cooling system to maintain the temperature of the sputtering head at 10° C.-20° C., wherein a flow speed of circulating water in the forced water cooling system is 1-5 m/s; once the sputtering chamber is vacuumized to a level below 6×10.sup.−4 Pa, introducing an argon gas into the sputtering chamber at a flow rate of 20-30 mL/min, and then maintaining a pressure in the sputtering chamber at 0.6-2.0 Pa; starting a power supply of the sputtering head at a power of 10-100 W to allow deposition of the bismuth film on the substrate for a period of 1 minute to 2 hours, wherein a thickness of the bismuth film is regulated by adjusting a length of the period; and (3) continuously introducing the argon gas, and regulating the heating temperature to 274° C.-350° C. to maintain the bismuth film in the semi-molten state; once a substrate temperature is stable, introducing a mixture of the argon gas and an oxygen gas for 5 minutes to 2 hours to form the bismuth oxide nanowire film.

3. The method according to claim 1, wherein the bismuth target is made of bismuth.

4. The method according to claim 1, wherein the step of washing the substrate comprises: subjecting the substrate to a first ultrasonic treatment in propanone, then subjecting the substrate to a second ultrasonic treatment in ethanol, and blow drying the substrate with nitrogen gas.

5. The method according to claim 1, wherein the substrate is made of fluorine-doped tin oxide (FTO), indium tin oxide (ITO), Si, Si/SiO.sub.2, glass, quartz, platinum, stainless steel, nickel, or copper.

6. The method according to claim 2, wherein, in step (3), the oxygen gas is introduced at a flow rate of 1-10 mL/min, and the argon gas is introduced at a flow rate of 20-30 mL/min.

7. The method according to claim 2, wherein the rotation stage rotates at 5-30 r/min.

8. A method for using the bismuth oxide nanowire film prepared by the method of claim 1 comprising: directly using the bismuth oxide nanowire film as a catalyst or a carrier for other catalysts to form a photoelectrocatalytic electrode.

9. The use method according to claim 8, comprising: loading a layer of CuBi.sub.2O.sub.4 on the bismuth oxide nanowire film to form the photoelectrocatalytic electrode.

10. The method according to claim 2, wherein the bismuth target is made of bismuth.

11. The method according to claim 2, wherein the step of washing the substrate comprises: subjecting the substrate to a first ultrasonic treatment in propanone, then subjecting the substrate to a second ultrasonic treatment in ethanol, and blow drying the substrate with nitrogen gas.

12. The method according to claim 2, wherein the substrate is made of fluorine-doped tin oxide (FTO), indium tin oxide (ITO), Si, Si/SiO.sub.2, glass, quartz, platinum, stainless steel, nickel, or copper.

13. The method according to claim 8, wherein the method for preparing the bismuth oxide nanowire film by heating in the upside down position comprises: (1) washing the substrate, and fixing the substrate to the substrate support in a sputtering chamber of the magnetron sputtering system in the position; placing the bismuth target on the sputtering head in the magnetron sputtering system, wherein the sputtering head is provided with a forced water cooling system, and the forced water cooling system is configured to maintain a temperature of the sputtering head at 10° C.-20° C.; closing a cover of the sputtering chamber; (2) vacuumizing the sputtering chamber, starting a rotation stage to rotate, heating the substrate to 25° C.-274° C., and starting the forced water cooling system to maintain the temperature of the sputtering head at 10° C.-20° C., wherein a flow speed of circulating water in the forced water cooling system is 1-5 m/s; once the sputtering chamber is vacuumized to a level below 6×10.sup.−4 Pa, introducing an argon gas into the sputtering chamber at a flow rate of 20-30 mL/min, and then maintaining a pressure in the sputtering chamber at 0.6-2.0 Pa; starting a power supply of the sputtering head at a power of 10-100 W to allow deposition of the bismuth film on the substrate for a period of 1 minute to 2 hours, wherein a thickness of the bismuth film is regulated by adjusting a length of the period; and (3) continuously introducing the argon gas, and regulating the heating temperature to 274° C.-350° C. to maintain the bismuth film in the semi-molten state; once a substrate temperature is stable, introducing a mixture of the argon gas and an oxygen gas for 5 minutes to 2 hours to form the bismuth oxide nanowire film.

14. The method according to claim 8, wherein the bismuth target is made of bismuth.

15. The method according to claim 8, wherein the step of washing the substrate comprises: subjecting the substrate to a first ultrasonic treatment in propanone, then subjecting the substrate to a second ultrasonic treatment in ethanol, and blow drying the substrate with nitrogen gas.

16. The method according to claim 8, wherein the substrate is made of fluorine-doped tin oxide (FTO), indium tin oxide (ITO), Si, Si/SiO.sub.2, glass, quartz, platinum, stainless steel, nickel, or copper.

17. The method according to claim 13, wherein, in step (3), the oxygen gas is introduced at a flow rate of 1-10 mL/min, and the argon gas is introduced at a flow rate of 20-30 mL/min.

18. The method according to claim 13, wherein the rotation stage rotates at 5-30 r/min.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 shows the steps for preparing a bismuth oxide nanowire film.

[0022] FIG. 2 is a scanning electron microscope (SEM) image of the bismuth film produced in Example 1.

[0023] FIG. 3 is a scanning electron microscope (SEM) image of the bismuth oxide nanowire film produced in Example 1.

[0024] FIG. 4 shows the chopped photocurrent-potential curves of the electrodes consisting of bismuth oxide nanowires/CuBi.sub.2O.sub.4 catalyst in Application Example 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The following description is to further describe the present invention, rather than limiting the scope of present invention.

Example 1: A Method for Preparing a Bismuth Oxide Nanowire Film

[0026] As shown in FIG. 1, the method comprises the following steps: [0027] (1) A substrate was firstly subjected to ultrasonic treatment in propanone for 10 minutes and in ethanol for 10 minutes, and then blow-dried with nitrogen gas. The washed substrate was fixed to a substrate support in a sputtering chamber of the magnetron sputtering system in such a position that the electrically conductive surface of the substrate faced downwards. A high-purity bismuth target adhered to a copper backing plate was placed on the sputtering head in the magnetron sputtering system wherein the sputtering head was provided with a forced water cooling system. Then, the cover of the sputtering chamber was closed. [0028] (2) The sputtering chamber was vacuumized, and the rotation stage was started up to rotate at 5-15 r/min. The substrate was then heated to 25° C.-150° C., and the forced water cooling system was started up to maintain the temperature of the sputtering head at 10° C.-15° C., wherein a flow speed of circulating water in the forced water cooling system was 1-2 m/s. Once the sputtering chamber was vacuumized to a level below 6×10.sup.−4 Pa, argon gas was introduced into the sputtering chamber at a flow rate of 20-25 mL/min, and then the pressure in the sputtering chamber was maintained at 0.6-1.0 Pa. [0029] (3) The power supply of the sputtering head was started up at a power of 10-60 W. Once a stable glow was observed, the baffle of the substrate support was moved away to allow deposition of a bismuth film on the substrate for a period of 1 minute to 1 hour, wherein a thickness of the bismuth film was regulated by adjusting the a length of the period; [0030] (4) As the argon gas was introduced continuously, the heating temperature was precisely regulated to 274° C.-300° C. to maintain the bismuth film in a semi-molten state. Once the substrate temperature was stable, a mixture of argon gas and oxygen gas was introduced to allow oxidation over the film for 5-60 minutes to form the nanowire structure, wherein the oxygen gas was introduced at a flow rate of 5-10 mL/min, and the argon gas was introduced at a flow rate of 20-25 mL/min.

[0031] FIG. 2 and FIG. 3 are respectively scanning electron microscope (SEM) images showing the morphology of bismuth film before heating and the morphology of bismuth oxide nanowire film after heating. The images clearly show the drop-like structure of bismuth before heating and the bismuth oxide nanowire structures formed on the substrate after heating.

Example 2

[0032] The method was performed identical to Example 1 except that the rotation stage rotated at 15-30 r/min.

Example 3

[0033] The method was performed identical to Example 1 except that the temperature of the sputtering head was maintained at 15° C.-20° C., and a flow speed of circulating water in the forced water cooling system was 2-5 m/s.

Example 4

[0034] The method was performed identical to Example 1 except that the oxygen gas was introduced at a flow rate of 1-5 mL/min, and the argon gas was introduced at a flow rate of 25-30 mL/min.

Example 5

[0035] The method was performed identical to Example 1 except that the pressure in the sputtering chamber was maintained at 1.0-2.0 Pa.

Example 6

[0036] The method was performed identical to Example 1 except that the power on the target was 60-100 W.

Example 7

[0037] The method was performed identical to Example 1 except that the substrate was heated to 150° C.-274° C., and the deposition of the bismuth film on the substrate was carried out for a period of 1 hour to 2 hours.

Example 8

[0038] The method was performed identical to Example 1 except that the heating temperature was regulated to 300° C.-350° C., and the oxidation over the film was carried out for 60 minutes to 2 hours to form the nanowire structure.

Application Example 1

[0039] A layer of CuBi.sub.2O.sub.4 was loaded on the bismuth oxide nanowire film obtained in Example 1 to give a bismuth oxide nanowire/CuBi.sub.2O.sub.4 electrode. A chopped-illumination test was carried out on the bismuth oxide nanowire/CuBi.sub.2O.sub.4 electrode, a CuBi.sub.2O.sub.4 electrode, and a bismuth oxide nanowire electrode:

[0040] Photoelectrochemistry measurements were performed in a three-electrode configuration, with a solution comprising 0.3 mol/L of potassium sulfate and 0.2 mol/L of phosphate as electrolyte, under chopped illumination from an AM 1.5G (100 mW/cm.sup.2) xenon lamp. The bismuth oxide nanowire/CuBi.sub.2O.sub.4 electrode, the CuBi.sub.2O.sub.4 electrode, and the bismuth oxide nanowire electrode served as the working electrodes. Ag/AgCl and Platinum were employed as the reference and counter electrodes, respectively.

[0041] FIG. 4 shows the chopped photocurrent-potential curves of the bismuth oxide nanowire/CuBi.sub.2O.sub.4 electrode, the CuBi.sub.2O.sub.4 electrode, and the bismuth oxide nanowire electrode. It can be seen from the curves that the bismuth oxide nanowire/CuBi.sub.2O.sub.4 electrode exhibited excellent photoresponse, with a large increase in photocurrent density as compared with the CuBi.sub.2O.sub.4 electrode and the bismuth oxide nanowire electrode. It can also be seen from the curves that the bismuth oxide nanowire film obtained in Example 1 exhibited photoresponse under illumination, indicating that the bismuth oxide nanowire film can be directly used as a catalyst. It should be noted that, the bismuth oxide nanowire/CuBi.sub.2O.sub.4 electrode exhibited a large increase in dark current density as compared with the CuBi.sub.2O.sub.4 electrode and the bismuth oxide nanowire electrode, indicating that the bismuth oxide nanowire films produced by the present invention have very high application value in electrocatalysis.