TWI394868B - Photocatalytic electrodes for use in hydrogen-generating photoelectrochemical cells and method of making the same - Google Patents

Description

Photocatalyst electrode for photoelectrochemical hydrogen production reactor and manufacturing method thereof

The invention relates to a photocatalyst electrode for a photoelectrochemical hydrogen production reactor and a preparation method thereof, in particular to a photocatalyst electrode formed by using a powder photocatalyst slurry, in particular, as an anode in a photoelectrochemical hydrogen production reactor. .

Photoelectrochemical Cell (PEC), which is still in the development stage of water decomposition, has two main structures, one single cell (Single Cell or Undivided Cell), that is, the yin and yang bipolar chambers are not separated; One is a double cell or a separate cell (Double Cell or Divided Cell), that is, the anode and cathode chambers are separated by appropriate partitions. Among them, the former often uses a photocatalyst suspension to generate water decomposition. Although the operation is simple, since it cannot separate the hydrogen and oxygen generated by the decomposition of water, it is not only dangerous to operate, but also cannot effectively utilize the generated hydrogen as a fuel. Therefore, Sacrificial Reagents such as methanol and sodium sulfite are commonly used to suppress the formation of oxygen. However, the use of sacrificial reagents is not only wasteful, but also produces improper by-products, so it is still not effective for the process of water decomposition to produce hydrogen in large quantities. As for the latter, since it can effectively separate hydrogen and oxygen, it can be safely operated, and is more suitable for practical hydrogen production applications. Therefore, it is a general trend to use a two-tank photoelectrochemical reactor to decompose water to produce hydrogen.

Generally, a two-tank photoelectrochemical reactor must have a photocatade that receives light and a dark cathode that is made of platinum catalyst without being exposed to light. In an acidic aqueous solution, when a photoanode catalyst, such as titanium dioxide (TiO ₂ ), is irradiated by a suitable light source (hv) to generate electrons and holes (Electron/Hole Pair); the hole (h ⁺ ) decomposes water. The molecules produce oxygen and hydrogen ions, and the electrons (e ^- ) are transferred to the dark cathode via the outer loop circuit and the hydrogen ions are reduced to form hydrogen. The response is as follows:

Photocatalyst is excited: (TiO ₂ )+2hv→2h ⁺ +2e ^-

Photoanode reaction: H ₂ O+2h ⁺ →2H ⁺ +1/2O ₂

Dark cathode reaction: 2H ⁺ +2e ^- → H ₂

Total reaction: (TiO ₂ )+2hv+H ₂ O→H ₂ +1/2O ₂

Thereby, the action of the visible light catalyst electrode dominates the reaction of the entire water to decompose hydrogen. Therefore, a well-made photocatalyst electrode is one of the most important rings for the composition of the photoelectrochemical reactor.

According to the production of photocatalyst electrodes, various methods have been developed, such as vacuum sputtering, anodizing, and sol sintering. At present, it is mainly deposited by using a photocatalyst sol (Sol Gel) on a metal substrate, such as a titanium metal sheet, and then calcined at a high temperature. However, as shown in Fig. 4, the modified visible TiO 2 photocatalyst electrode having an area of 2 cm x 2 cm prepared by the above sol sintering method is irradiated with an Air Mass 1.5 (AM 1.5) standard light source in a 0.1 M aqueous sulfuric acid solution, and The photocatalyst electrode obtained by using silver/silver chloride (Ag/AgCl) as a reference electrode, platinum platinum counter electrode, and a linear scanning speed of 50 mV/s (mV/s) under normal conditions, It can be seen from the light current curve 4 and the dark current curve 5 that the difference between the two is its photocurrent. It can be clearly seen from the figure that its photocurrent is only 0.3 milliamperes (mA). It can be seen that the photocatalyst has a low adhesion amount and the water decomposition effect is not good, so it is difficult to achieve the goal of commercial application. Many photocatalysts synthesized as powdery solids cannot be fabricated into electrodes by this method. Therefore, the general practitioners cannot meet the needs of the user in actual use.

SUMMARY OF THE INVENTION The primary object of the present invention is to overcome the above problems encountered in the prior art and to provide a photocatalyst electrode constructed using a powdered photocatalyst and as an anode in a photoelectrochemical hydrogen production reactor.

A secondary object of the present invention is to provide an electrode capable of processing a powder photocatalyst which is difficult to process into an electrode for photoelectrochemical hydrogen production reactor, and to easily adjust the composition of the electrode catalyst layer, thereby achieving good performance. .

For the purpose of the above, the present invention is a photocatalyst electrode for a photoelectrochemical hydrogen production reactor and a method for fabricating the same, which is an electrode formed by a powder photocatalyst and can be used as an anode in a hydrogen production reactor, which comprises a carbonaceous electrode. The substrate and a photocatalyst layer coated on the carbonaceous electrode substrate are formed. Here, the photocatalyst layer is composed of a slurry in which a powder photocatalyst, an ion coupling agent, and a conductive carbon powder are mixed, and is uniformly applied to the carbonaceous electrode substrate.

Please refer to FIG. 1 and FIG. 2 for a schematic view of the structure of the present invention and a schematic diagram of the flow of the present invention. As shown in the figure: the present invention is a photocatalyst electrode for photoelectrochemical hydrogen production reactor using a powder photocatalyst, and a method for fabricating the same, which is suitable for use in an anode in a photoelectrochemical hydrogen production reactor, comprising a carbonaceous electrode substrate 11 And a photocatalyst layer 12 coated on the carbonaceous electrode substrate 11 can effectively solve the problem that the electrode is not easily processed by using a powder photocatalyst, and the composition of the electrode catalyst can be easily regulated.

The carbonaceous electrode substrate 11 is a carbon cloth or a non-catalyzed gas diffusion electrode (Non-catalyzed Gas Diffusion Electrode). The photocatalyst layer 12 coated on the carbonaceous electrode substrate 11 is composed of a slurry of a powder photocatalyst, an ion coupling agent and a conductive carbon powder, wherein the powder photocatalyst and the conductive carbon powder The range of ratios is not limited, it can be a variety of, and 5:1 is the best. As described above, a photocatalyst electrode 1 of a photoelectrochemical hydrogen production reactor using a powder photocatalyst is constructed.

The photocatalyst electrode 1 is suitable for the anode of a photoelectrochemical reactor for hydrolyzing hydrogen production, and the manufacturing process thereof is as shown in FIG. 2, and includes at least the following steps:

(A) mixing a powder photocatalyst 111 with an ion-bonding agent 112 and a conductive carbon powder 113 in a container, vibrating for a few minutes by ultrasonic wave, and stirring to prepare a uniformly mixed photocatalyst slurry, wherein the ion-bonding The agent 112 is a perfluoropolystyrene sulfonic acid (Nafion) solution containing an ion exchanger (Ionomer), and the powder photocatalyst 111 is Visible Light-Driven Photo-catalysts, such as bismuth vanadate (BiVO). ₄ ), and VU-Responsive Photo-catalysts, such as titanium dioxide (TiO ₂ ), and the conductive carbon powder 113 is a conventional conductive carbon black, such as Vulcan XC72 carbon black and single tube (Single -Walled) or Multi-Walled Carbon Nanotube carbon nanotubes;

(B) uniformly applying the prepared photocatalyst slurry to a carbonaceous electrode substrate 11 so that the photoelectrode catalyst completely covers the carbonaceous electrode substrate 11 to form a photocatalyst layer 12;

(C) The photocatalyst layer 12 is flattened and dried to form a photocatalyst electrode 1.

The above is the photocatalyst electrode obtained by a simple catalyst slurry coating method using a powder photocatalyst according to the present invention, and various suitable powder photocatalysts can be used as the anode in the photoelectrochemical hydrogen production reactor.

When the present invention is formulated, in a preferred embodiment, an electrode composed of a commercial titanium dioxide (Degussa P25) photocatalyst is used as the anode of the photoelectrochemical hydrogen production reactor, and the steps thereof include:

(A1) A 100 mg Degussa P25 titanium dioxide photocatalyst was mixed with a 0.5 ml Nafion solution at a concentration of 20% and a 20 mg Vulcan XC72 conductive carbon powder in a small beaker and oscillated by ultrasonic waves. Minute and manual stirring for about 10 minutes to prepare a uniformly mixed photocatalyst slurry;

(B1) A non-hydrophobic treated carbon cloth (ElectroChem, EC-CC1-060) is used as an electrode substrate, and is placed on a glass plate in a square size of 2 cm x 2 cm, and then the above is prepared. The photocatalyst slurry is uniformly coated on the electrode substrate, and the photoelectrode catalyst is completely coated on the electrode substrate to form a photocatalyst layer;

(C1) The electrode substrate coated with the photocatalyst layer is coated with a polyvinyl chloride (PVC) film, and subjected to a pressure of 10 atmospheres at room temperature for 20 minutes using a flat plate press. After the photocatalyst layer is smooth and uniform, the electrode substrate coated with the photocatalyst layer is dried in the air for 3 days to form a photocatalyst electrode.

In order to prove that the photocatalyst electrode system prepared by the invention can generate extremely high photocurrent, it is suitable as an anode used in a photoelectrochemical hydrogen production reactor, so it is irradiated with a standard light source of Air Mass 1.5 (AM1.5) in a 0.1 M sulfuric acid aqueous solution, and It was carried out at room temperature with silver/silver chloride (Ag/AgCl) as the reference electrode and platinum platinum counter electrode at a linear scanning speed of 50 mV/s. Please refer to FIG. 3, which is a schematic diagram of the anode current curve of the photocatalyst electrode of the present invention under illumination and no light. As shown in the figure, it can be seen from the photocatalytic electrode 2 and the dark current curve 3 of the photocatalyst electrode of the present invention that the difference between the two is its photocurrent. When the voltage is greater than 1.05V (Ag/AgCl), the photocurrent starts to be generated, and when it is above 1.5V (Ag/AgCl), the photocurrent reaches a steady state. It can be clearly seen from the upper left corner of the figure that the photocurrent is about 2.5 milliamperes (mA).

Comparing with the same area of titanium dioxide photocatalyst electrode made by the prior art under the same experimental conditions (refer to Fig. 4), it can be clearly known that the photocurrent measured by the prior art is 0.3 mA, only about this 1/8 of the photoelectrode produced by the invention. It can be seen that the photocatalyst electrode produced by the present invention has excellent photocurrent generating performance, which is sufficient to prove that the electrode of the present invention is suitable for use as an anode in a photoelectrochemical hydrogen production reactor.

In addition, when the content of the photocatalyst and the conductive carbon powder was changed while maintaining the content of the ionic bonding agent (20% Nafion solution), it was found that the photocurrent generated by the photocatalyst electrode was also changed. The photocurrent generated by the ratio of the weight of the two is preferably 5:1. In general, the photocatalyst used in the electrode of the present invention can be easily adjusted, and the photocatalyst used can also use any powder. The photoelectrode catalyst layer combined by the ion bonding agent has a porous large-area structure. Therefore, it can generate a higher photocurrent than the photocatalyst electrode produced by other methods.

In summary, the present invention is a photocatalyst electrode of a photoelectrochemical hydrogen production reactor and a manufacturing method thereof, which can effectively improve various disadvantages of the conventional use, and can form a photocatalyst capable of photoelectrochemical hydrogen production by using a powder photocatalyst which is difficult to process. The electrode is used, and the composition of the photo-electrode catalyst layer is easily regulated to obtain good performance, thereby making the invention more progressive, more practical, and more suitable for the user, and has indeed met the invention patent application. Essentials, 提出 file a patent application in accordance with the law.

However, the above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto; therefore, the simple equivalent changes and modifications made in accordance with the scope of the present invention and the contents of the invention are modified. All should remain within the scope of the invention patent.

(part of the invention)

1. . . Photocatalyst electrode

11. . . Carbonaceous electrode substrate

111. . . Powder photocatalyst

112. . . Ion linker

113. . . Conductive toner

12. . . Photocatalyst layer

2. . . Photocurrent curve

3. . . No photocurrent curve

(customized part)

4. . . Photocurrent curve

5. . . No photocurrent curve

Fig. 1 is a schematic view showing the structure of the present invention.

Fig. 2 is a schematic flow chart of the present invention.

Fig. 3 is a schematic view showing the anode current curve of the photocatalyst electrode of the present invention in the presence of light and no light.

Figure 4 is a schematic diagram showing the anode current curve of a conventional photocatalyst electrode in the presence of light and no light.

1. . . Photocatalyst electrode

11. . . Carbonaceous electrode substrate

12. . . Photocatalyst layer

Claims (10)

A photocatalyst electrode for a photoelectrochemical hydrogen production reactor is suitable for use in an anode of a photoelectrochemical hydrogen production reactor for decomposing water, comprising: a carbonaceous electrode substrate; and a photocatalyst layer coated on the carbonaceous material On the electrode substrate, the photocatalyst layer is composed of a slurry of a powder photocatalyst, an ion coupling agent and a conductive carbon powder, wherein the ratio of the powder photocatalyst to the conductive carbon powder is 5:1. . The photocatalyst electrode of the photoelectrochemical hydrogen production reactor according to claim 1, wherein the carbonaceous electrode substrate is a carbon cloth, a carbon paper or a non-catalyst gas diffusion electrode. (Non-catalyzed Gas Diffusion Electrode). The photocatalyst electrode of the photoelectrochemical hydrogen production reactor according to claim 1, wherein the powder photocatalyst is Visible Light-Driven Photo-catalysts and may be BiVO ₄ . . The photocatalyst electrode of the photoelectrochemical hydrogen production reactor according to claim 1, wherein the powder photocatalyst is a VU-Responsive Photo-catalyst, and may be titanium dioxide (TiO ₂ ). The photocatalyst electrode of the photoelectrochemical hydrogen production reactor according to claim 1, wherein the ion linker is a perfluoropolystyrenesulfonic acid (Nafion) solution containing an ion exchanger (Ionomer). The photocatalyst electrode of the photoelectrochemical hydrogen production reactor according to claim 1, wherein the conductive carbon powder is a conventional conductive carbon black. The photocatalyst electrode of the photoelectrochemical hydrogen production reactor according to claim 6, wherein the conductive carbon black is selected from the group consisting of Vulcan XC72 carbon black and Single-Walled or Multi-Walled Carbon. Nanotube) Nano carbon tube. A photocatalytic electrode manufacturing method for a photoelectrochemical hydrogen production reactor comprises at least the following steps: (A) mixing a powder photocatalyst with an ion bonding agent and a conductive carbon powder in a container, oscillating by ultrasonic waves, and Stirring to form a uniformly mixed photocatalyst slurry; (B) uniformly coating the prepared photocatalyst slurry on a carbonaceous electrode substrate, and completely forming the photoelectrode catalyst on the carbonaceous electrode substrate a photocatalyst layer; and (C) flattening the photocatalyst layer to form a photocatalyst electrode. The photocatalyst electrode of the photoelectrochemical hydrogen production reactor according to claim 8, wherein the ion linker is a Nafion solution having an ion exchanger and a concentration of 20%. The photocatalyst electrode of the photoelectrochemical hydrogen production reactor according to claim 8, wherein the powder photocatalyst and the conductive carbon powder are preferably in a ratio of 5:1.