JP2775771B2 - Manufacturing method of fuel electrode catalyst for liquid fuel cell - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing a fuel electrode catalyst used in a liquid fuel cell using a reducing agent such as methanol, hydrazine or formalin as a liquid fuel and using air and oxygen as an oxidizing agent. It is about.

2. Description of the Related Art Liquid fuel cells include an alkaline type using a potassium hydroxide aqueous solution as an electrolyte and an acidic type using a sulfuric acid aqueous solution.
It is common to use air as an oxidizing agent in consideration of economy. From this point of view, many studies have been made on acidic liquid fuel cells in which the electrolyte does not deteriorate even when air is used. In order to improve the characteristics of this type of fuel cell, there is a great deal of involvement in the method of producing a noble metal catalyst used for an electrode. In particular, it is an important technology to carry noble metal catalyst particles in a highly dispersed state on carbon particles. Therefore, many studies have been made on a method for supporting a noble metal catalyst. For example, in a method for producing a noble metal catalyst, a platinum complex compound is oxidized with an oxidizing agent to produce colloidal particles of an oxidation product, which are precipitated on a conductive carbon substrate, and then the carbon is washed, washed and dried. . Thereafter, it has been proposed that platinum oxide precipitated on the carbon substrate is reduced with hydrogen to form platinum particles of the catalyst in a highly dispersed state (Japanese Patent Publication No. 61-1869), but the platinum catalyst alone is not used. Slightly fine catalyst particles of about 10-20 mm are supported on the carbon substrate in a highly dispersed state. However, the platinum catalyst alone is not practical because the properties of the methanol electrode of a liquid fuel cell are poor and impractical. Many alloy catalysts have been studied. Although this platinum-ruthenium binary catalyst has been studied for a fuel electrode catalyst of a phosphoric acid fuel cell, the method for preparing this fuel electrode catalyst cannot be used as it is for a methanol electrode catalyst of a liquid fuel cell.

For example, after dispersing a hydrophilically-treated catalyst carrier (fine carbon particles) in water, adding chloroplatinic acid and an aqueous ruthenium chloride solution thereto, adjusting the PH to the alkali side, and then using a colloid aggregation inhibitor at a temperature at which the reaction is possible. (Hydrogen peroxide)
Furthermore, there has been proposed a method for preparing a white-ruthenium alloy catalyst by heat-treating a mixed platinum-ruthenium catalyst obtained by gradually adding a reducing agent (Japanese Patent Application Laid-Open No. 63-4876).
No. 1). In this catalyst preparation method, homogeneous mixing of platinum and ruthenium catalyst in the presence of a catalyst carrier (carbon fine powder), P
It is difficult to support the catalyst carrier (fine carbon powder) in a highly dispersed state without uniform precipitation on the surface of the pores in order to advance the alkali adjustment of H, the reduction reaction of the catalyst salt by the reducing agent, etc. It is. Accordingly, the specific surface area of the catalyst particles varies greatly, and excellent characteristics may not be obtained even when used as a methanol electrode of a liquid fuel cell. Therefore, in order to make further improvements, a reducing agent (for example, sodium bisulfite) is gradually added to a mixed aqueous solution containing chloroplatinic acid and ruthenium chloride at a temperature at which the reaction is possible, and the pH is adjusted to an acidic side. An appropriate amount of aqueous hydrogen oxide solution was added to prepare a homogeneous and highly dispersed colloidal dispersion composed of platinum and ruthenium. While maintaining this state, we propose to add a catalyst carrier (fine carbon powder), and form a highly dispersed platinum-ruthenium catalyst with small variations of about 10 to 30 mm on the surface of fine carbon particles. I was able to make it. This could be observed from a transmission electron microscope. However, the following problems occurred.

Problems to be Solved by the Invention In such a conventional method for producing a catalyst, even when a platinum / ruthenium catalyst is supported on the surface of carbon fine particles in a highly dispersed state, the catalyst is used for a methanol electrode of a liquid fuel cell. There was a problem that characteristics could not be obtained. It showed almost the same characteristics as the case of the platinum catalyst alone of the reference. When this catalyst was examined by X-ray diffraction, peaks of platinum and ruthenium appeared, and it was found that platinum and ruthenium were present alone on the surface of the carbon fine particles. Moreover, when the particle size of the catalyst was measured by the CO adsorption method, it showed a particle size of about 10 to 20 mm, indicating that the catalyst was highly dispersed alone. Focusing on the fact that when the catalyst is supported on carbon fine particles in a state where the platinum compound salt and the ruthenium compound salt are simultaneously mixed, the two do not aggregate, and the catalyst is supported alone in the form of fine particles. In addition to the preparation method, it was considered that by performing heat treatment in a non-oxidizing atmosphere in this highly dispersed state, alloying of platinum and ruthenium was promoted and high activity was obtained.

The present invention solves such a problem, and in particular,
A carbon fine powder in a suspended state is added to a colloidal dispersion of a mixed catalyst comprising at least two of platinum, ruthenium and tin on the surface of the carbon fine particles to precipitate the mixed catalyst in a highly dispersed state, and then to perform non-oxidation. It is an object of the present invention to obtain a method for producing a fuel electrode catalyst for a liquid fuel cell, which has a step of supporting a highly active catalyst by heat treatment in a neutral atmosphere to alloy the mixed catalyst.

Means for Solving the Problems In order to achieve the above object, the present invention provides a method for supporting a highly active alloy catalyst on carbon fine particles of a fuel electrode for a liquid fuel cell. To a mixed aqueous solution in which at least two kinds of salts of a salt and a tin compound are dissolved, a reducing agent is gradually added at a temperature at which the reaction can be performed to adjust the pH, and then an aqueous solution of hydrogen peroxide is added to form a mixture of platinum, ruthenium, A carbon fine powder in a suspended state is added to a colloidal dispersion liquid containing two or more types of tin, and then the mixture is washed, dried, and dried. This is a method for producing a fuel electrode catalyst for a liquid fuel cell, which is heat-treated at the temperature of In this manufacturing process, a step of mixing two or more of platinum-containing color salt, ruthenium compound salt and tin compound salt while performing high dispersion treatment using an ultrasonic disperser, For producing a fuel electrode catalyst for a liquid fuel cell, comprising a step of adding a carbon fine powder in a suspended state to a colloidal dispersion composed of at least two of platinum, ruthenium and tin during high dispersion treatment using a disperser. What you get.

As the next invention, the pH is adjusted by gradually adding a sodium bisulfite solution at a reaction temperature to a mixed aqueous solution in which at least two salts of a platinum compound salt, a ruthenium compound salt, and a tin compound salt are dissolved. After that, an aqueous solution of hydrogen peroxide is added, and at least one of before and after adding the suspended carbon fine powder to the colloidal dispersion liquid comprising at least two of platinum, ruthenium, and tin, a reducing agent is added. A method for producing a fuel electrode catalyst for a liquid fuel cell in which a mixed catalyst-supported carbon fine powder obtained by drying is heat-treated at a temperature of 700 to 1000 ° C. in a non-oxidizing atmosphere at a temperature of 700 to 1000 ° C. Sodium bisulfite, sodium hydrogen carbonate, sodium formate, sodium dithionate, sodium tartrate, sodium citrate, hydrazine, formalin or alcohol Method of manufacturing a liquid fuel cell anode catalyst is either Le is intended to obtain.

According to such a method for producing an anode catalyst, a reducing agent is gradually added to a mixed aqueous solution in which at least two kinds of salts of a platinum compound salt, a ruthenium compound salt, and a tin compound salt are dissolved,
A step (I) of preparing a colloidal dispersion comprising at least two of platinum, ruthenium and tin by adding an aqueous solution of hydrogen peroxide after reducing each salt, and a colloidal dispersion in which the catalyst particles are in a highly dispersed state. Add suspended carbon fine powder to the liquid,
The step (II) of precipitating the catalyst alone in a highly dispersed state on the surface of the carbon fine particles, and the heat treatment of the finely divided carbon powder carrying the catalyst in a non-oxidizing atmosphere (III), The platinum, ruthenium, and tin catalyst particles supported alone in a highly dispersed state become sintered, and when the platinum, ruthenium, and tin atoms are in contact with each other, the metal atoms diffuse into one another to form an alloy or a solid solution. And the activity of the catalyst is greatly improved. It is also known that platinum-ruthenium, platinum-tin, ruthenium-tin, and platinum-ruthenium-tin catalysts each have higher catalytic activity than single catalysts. As described above, the catalyst exhibits high activity in the process of heat treatment in a state of being highly dispersed on the carbon fine particles, thereby greatly improving the characteristics of the fuel electrode for a liquid fuel cell.

Examples Hereinafter, examples will be described in more detail.

Example 1 A commercially available fine carbon powder (acetylene black, carbon black, activated carbon, etc.) was immersed in a nitric acid aqueous solution or the like.
After the hydrophilization treatment, this carbon fine powder was washed and dried to obtain a catalyst-supporting carbon carrier. Next, a solution of 10 g of commercially available chloroplatinic acid (H ₂ PtCl ₆ ) in 1 water was added with 12 g /
A ruthenium chloride (RuCl ₃ ) aqueous solution 1 having a concentration of 1 was gradually added to form a mixed solution. Next, 100 g of an aqueous solution of sodium bisulfite (NaHSO ₃ ) / 100 ml of an aqueous solution is gradually and continuously added to the mixed solution, and the solution is added with an aqueous solution of sodium hydroxide (NaOH) or the like.
The pH was adjusted to 4 to 6, and 100 ml of a 30 vol% aqueous hydrogen peroxide (H ₂ O ₂ ) solution, which was at least 10 times the required amount, was added to form a colloidal dispersion of platinum and ruthenium. Suspended carbon fine powder (for example, BP-200 manufactured by Cabot Corporation) in which 50 g of water and fine carbon powder were subjected to high dispersion treatment in advance using an ultrasonic disperser to this dispersion liquid.
0 carbon black) to precipitate the platinum-ruthenium catalyst into fine carbon particles. Next, the platinum fine-ruthenium mixed catalyst-supported carbon fine powder obtained by excess, washing and drying is heat-treated at a temperature of about 800 ° C. in a non-oxidizing atmosphere, for example, vacuum, to form an alloy or a solid solution of the catalyst. Further promoted. A dispersion of a fluororesin (polytetrafluoroethylene) is added to the platinum-ruthenium alloy catalyst-supported carbon fine powder to form a paste. The paste is applied via conductive carbon paper, dried and dried to form an electrode substrate. did.
A lead was attached to this electrode substrate to form a methanol electrode. In order to evaluate the monopolar potential characteristics of the methanol electrode, the monopolar potential of the methanol electrode with respect to the hydrogen electrode potential was measured in combination with a hydrogen standard electrode. The methanol electrode manufactured in the first embodiment is denoted by A.

Example 2 A 12 g / concentration ruthenium chloride (RuCl ₃ ) aqueous solution 1 in a solution of 10 g of commercially available chloroplatinic acid (H ₂ PtCl ₆ ) in 1 water was subjected to ultrasonic dispersion treatment using an ultrasonic disperser. And then gradually and continuously add 100 g of an aqueous solution of sodium bisulfite (NaHSO ₃ ) / 100 ml of an aqueous solution to the mixed solution, and adjust the pH to 4 with an aqueous solution of sodium hydroxide (NaOH) or the like.
6 to adjust 30 vol% waiting hydrogen oxide (H ₂ O ₂₎ aqueous solution was added to 100ml of 10 times or more the necessary amount to form a colloidal dispersion of platinum and ruthenium, in advance ultrasonic disperser to the dispersion Suspended carbon fine powder (BP-2000 carbon black, manufactured by Cabot Corporation) obtained by highly dispersing 50 g of water and carbon fine powder is gradually added while performing ultrasonic polarization treatment using an ultrasonic disperser. The ruthenium catalyst was precipitated into fine carbon particles. In the following manufacturing steps, a methanol electrode was formed by the same manufacturing method as in Example 1, and the unipolar potential of the methanol electrode was measured. The methanol electrode produced in Example 2 is designated as B.

Example 3 A 1 g / concentration aqueous solution of tin chloride (SnCl ₂ ) 1 in a solution of 10 g of commercially available chloroplatinic acid (H ₁ PtCl ₆ ) dissolved in 1 water was subjected to ultrasonic dispersion treatment using an ultrasonic disperser. Process and gradually add fine powder carrying platinum and tin mixed catalyst
A methanol electrode was formed and the unipolar potential of the methanol electrode was measured by the same manufacturing method as in Example 1, except that the heat treatment at a temperature of 800 ° C. was performed in a nitrogen gas atmosphere. The methanol electrode manufactured in the third embodiment is designated as C.

Example 4 A 1 g / concentration aqueous solution of tin chloride (SnCl ₂ ) 1 in a solution of 12 g of commercially available ruthenium (RuCl ₃ ) dissolved in 1 water was gradually subjected to ultrasonic dispersion treatment using an ultrasonic disperser. Example 1 except that the manufacturing process added to the above and the manufacturing process in which the atmosphere conditions for heat-treating the mixed catalyst-supported fine powder of ruthenium and tin at a temperature of about 800 ° C. were in argon gas containing 2 to 10% hydrogen gas were used. A methanol electrode was formed by the same production method, and the unipolar potential of the methanol electrode was measured. The methanol electrode manufactured in Example 4 is denoted by D.

Example 5 12 g / concentration of ruthenium chloride (RuCl ₃ ) aqueous solution 1 and 2 g / concentration of tin chloride (SnCl ₃ ) aqueous solution in a solution of 10 g of commercially available chloroplatinic acid (H ₂ PtCl ₆ ) in 1 water 1 was gradually added while performing ultrasonic dispersion treatment using an ultrasonic disperser, and a methanol electrode was formed by the same manufacturing method as in Example 2 except for the manufacturing step of forming a mixed catalyst. It was measured. The methanol electrode manufactured in the fifth embodiment is denoted by E.

Example 6 In a solution of 10 g of commercially available chloroplatinic acid (H ₂ PtCl ₆ ) dissolved in 1 water, 12 g / aqueous ruthenium chloride (RuCl ₃ ) aqueous solution 1 was subjected to ultrasonic waves using an ultrasonic disperser. Add slowly and then add sodium bisulfite (Na
100 g of an aqueous solution of HSO ₃ ) / 100 ml of an aqueous solution is gradually and continuously added, and PH is adjusted to 4 to 6 with an aqueous solution of sodium carbonate (Na ₂ Co ₃ ).
After adding 100 ml of a 30 vol% hydrogen peroxide (H ₂ O ₂ ) aqueous solution at least 10 times the required amount to form a colloidal dispersion of platinum and ruthenium, an aqueous solution of sodium formate as an inorganic reducing agent (concentration After adding about 100 ml of 100 g /), 50 g of water and carbon fine powder were added to this dispersion in advance using an ultrasonic disperser.
Of carbon powder (BP-2000 carbon black, manufactured by Cabot) is gradually added while performing ultrasonic treatment using an ultrasonic disperser, and a platinum / ruthenium catalyst is precipitated on the carbon fine particles. A methanol electrode was formed by the same manufacturing method as in Example 1 after the manufacturing step of precipitation, and the unipolar potential of the methanol electrode was measured. The methanol electrode manufactured in Example 6 is denoted by F.

Example 7 12 g / concentration of ruthenium chloride (RuCl ₃ ) aqueous solution 1 and 2 g / concentration of tin chloride (SnCl ₃ ) aqueous solution in a solution of 10 g of commercially available chloroplatinic acid (H ₂ PtCl ₆ ) dissolved in 1 water 1 and a colloidal dispersion of platinum, ruthenium and tin is formed by gradually adding ultrasonic dispersion while using an ultrasonic disperser, and then water and carbon are added to this dispersion in advance by an ultrasonic disperser. A suspension of fine carbon powder (BP-2000 carbon black, manufactured by Cabot Corporation) in which 50 g of the fine powder is ultrasonically treated is gradually added while performing ultrasonic dispersing treatment using an ultrasonic dispersing machine. A methanol electrode was formed in exactly the same manner as in Example 1, except that a formalin solution was added in an appropriate amount and a platinum / ruthenium / tin catalyst was precipitated on carbon fine particles, and the unipolar potential of the methanol electrode was measured. The methanol electrode manufactured in Example 7 is denoted by G.

Comparative Example In the production method of Examples 1, 2, 3, 4, 5, 6, and 7, the carbon fine powder supporting each catalyst was not heat-treated in a non-oxidizing atmosphere, and methanol was left unheated. A pole was manufactured and used as a comparative example. The methanol electrode for this comparative example is a, b, c, d,
e, f, g. Therefore, except for the heat treatment step, all are the same as the manufacturing method of the first, second, third, fourth, fifth, sixth and seventh embodiments.

Table 1 shows the characteristics of the methanol electrode of this example and the comparative example. The measurement conditions were a 2MH ₂ SO ₄ aqueous electrolyte, a methanol concentration of 1.5 M, an operating temperature of 60 ° C., and a potential of the methanol electrode at a current density of 60 ma / cm ² . However, the potentials of the methanol electrode are all IR-free.

From Table 1, the characteristics of the methanol electrode of the present invention are 0.34 to 0.39.
In contrast to V, the characteristic of the conventional methanol electrode is 0.38 to 0.44V. Since all of these potentials are relative to the standard hydrogen electrode potential, the smaller the potential, the better the electrode. Therefore, A, B, C, D, E, F,
G is 0.03 to 0.05 more than conventional a, b, c, d, e, f, g
The characteristics are as good as V. In the present invention, the potential range is generated depending on the method of preparing the catalyst. However, all the characteristics are improved as compared with the conventional example, and it is understood that the heat treatment effect is large. In addition, the methanol electrode A, B, C, D, E,
FG and conventional methanol electrode a, b, c, d, e, f,
g was subjected to a life test at a temperature of 60 ° C. Battery density 60
measuring the potential E ₁ and the initial potential E ₀ after operating continuously for 5000 hours at ma / cm ^2, the deterioration rate I compared it. While the degradation rate of the conventional product was 10 to 20%, the degradation rate of the product of the present invention was about 1 to 3%, which indicates that the product of the present invention is a long-life electrode with excellent durability.
It is considered that by performing heat treatment in a non-oxidizing atmosphere at a temperature of 700 to 1000 ° C. as seen in the present invention, alloying further progresses between the metal particles and durability is increased.
On the other hand, in the conventional example, since the catalyst particles are only partially alloyed and exist in a single state, the activity of the catalyst itself is low and the corrosion resistance of the catalyst is not good. This is supported by the fact that a part of the catalyst is eluted in the electrolytic solution and the loading ratio is lowered.

Also in the examples A, B, C, D, E, F, and G, there are differences in the methanol electrode potential and the life. For example, comparing A and B, B is superior to A in both potential and lifetime. By introducing a process of high dispersion treatment when mixing the catalysts and mixing the mixed catalyst with the carbon fine powder, the catalyst is highly dispersed and supported on the surface of the carbon fine particles, thereby further improving the activity and durability of the catalyst. It is thought that there is. Next, CDD and E
In comparison, E is superior in both potential and life to C and D. A ternary catalyst composed of platinum, ruthenium, and tin has higher catalytic activity and a higher durability than a binary catalyst, such as platinum-tin or ruthenium-tin, in order to improve durability. And the life is extended. On the other hand, B
When comparing F, E, and G, there is no significant difference in the potential between B and F, and between E and G, but F and G are superior to B and E in life. This is achieved by adding an inorganic or organic reducing agent before and after precipitating the catalyst on the surface of carbon fine particles. However, F and G have higher mechanical strengths of the catalyst, hardly any falling off phenomenon, and a low degradation rate of the methanol electrode of about 1%.

As described above, when a catalyst is prepared by simultaneously mixing at least two or more platinum, ruthenium, and tin-based catalysts, the catalyst manufacturing process is simplified, the catalyst manufacturing cost can be reduced, and the performance of the methanol electrode can be reduced. Is greatly improved.

Although 800 ° C. was selected as an example of the heat treatment temperature in the present embodiment, a range of 700 ° C. to 1000 ° C. is appropriate. It has been confirmed by thermal differential analysis that alloying or solid solution formation of the catalyst particles proceeds in a non-oxidizing atmosphere within a range of 700 to 1000 ° C. When the temperature is lower than 700 ° C., alloying of the catalyst particles does not proceed. On the other hand, when the temperature is higher than 1000 ° C., aggregation of the catalyst particles is promoted and the activity of the catalyst is reduced. In order to maintain the activity of the catalyst at the highest level, the range is optimal. In an inert gas atmosphere, it is desirable to contain several percent of hydrogen gas. Oxidation may be suppressed by setting it in a slightly reducing atmosphere.

In this embodiment, chloroplatinic acid, ruthenium chloride, and tin chloride are selected as examples of platinum compound salts, ruthenium compound salts, and tin compound salts, but materials that are easily oxidized and reduced even when various other compounds are selected. Then, a similar effect can be expected.

On the other hand, sodium formate and formalin were selected as examples of the reducing agent during the preparation of the catalyst.
Inorganic reducing agents such as sodium bicarbonate, sodium dithionate, sodium tartrate, sodium citrate, hydrazine or organic reducing agents such as alcohols also work effectively.

In the present embodiment, a methanol fuel electrode is taken as an example of an electrode for a liquid fuel cell, but the present invention can also be applied to a hydrazine or formalin fuel electrode.

As described above, according to the present invention, at least two types of platinum, ruthenium, and tin catalysts are simultaneously supported on carbon fine particles in a highly dispersed state, and heat-treated at a temperature of 700 to 900 ° C. in a non-oxidizing atmosphere. It is possible to provide a method for manufacturing a catalyst for an electrode of a liquid fuel cell, which makes it possible to produce a high-performance fuel electrode and to simplify the catalyst manufacturing process and reduce the manufacturing cost. The effect is obtained.

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Makoto Uchida 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) H01M 4/88

Claims (6)

(57) [Claims] 1. A method for supporting a highly active alloy catalyst on carbon fine particles of a fuel electrode for a liquid fuel cell, wherein at least two of a platinum compound salt, a ruthenium compound salt and a tin compound salt are contained in an aqueous medium. A reducing agent is gradually added to the mixed aqueous solution in which the salt is dissolved at a temperature at which the reaction is possible to adjust the pH, and then an aqueous solution of hydrogen peroxide is added to disperse the colloid containing at least two of platinum, ruthenium, and tin. The suspended carbon fine powder is added to the liquid, and then the mixed catalyst-supported carbon fine powder obtained by excess, washing, and drying is mixed in a non-oxidizing atmosphere at 700 to 1 μm.
A method for producing a fuel electrode catalyst for a liquid fuel cell, comprising heat-treating at a temperature of 000 ° C. 2. The platinum compound salt, the ruthenium compound salt and the tin compound salt are chloroplatinic acid, ruthenium chloride and tin chloride, respectively. 2. The method for producing a fuel electrode catalyst for a liquid fuel cell according to claim 1, further comprising a step of gradually mixing in a state of each aqueous solution of tin. 3. A process for supporting two or more kinds of platinum, ruthenium and tin catalysts on carbon fine particles, wherein two or more kinds of platinum, ruthenium and tin undergoing high dispersion treatment using an ultrasonic disperser. 2. A method according to claim 1, further comprising the step of adding a carbon fine powder in a suspended state to the colloidal dispersion liquid containing the same.
13. The method for producing a fuel electrode catalyst for a liquid fuel cell according to claim 10. 4. The liquid fuel cell according to claim 1, wherein the reducing agent used to reduce at least two of the platinum compound salt, the ruthenium compound salt and the tin compound salt is sodium bisulfite. For producing a fuel electrode catalyst for use. 5. The pH is adjusted by gradually adding a sodium bisulfite solution to a mixed aqueous solution in which at least two salts of a platinum compound salt, a ruthenium compound salt and a tin compound salt are dissolved at a temperature at which the reaction is possible. After that, an aqueous solution of hydrogen peroxide is added, and a reducing agent is added to at least one of before and after adding the suspended carbon fine powder to a colloidal dispersion containing at least two of platinum, ruthenium, and tin, followed by filtration, Washing,
A method for producing a fuel electrode catalyst for a liquid fuel cell, comprising subjecting a mixed catalyst-supported carbon fine powder obtained by drying to a heat treatment at a temperature of 700 to 1000 ° C. in a non-oxidizing atmosphere. 6. A reducing agent used before and after a step of adding a carbon fine powder in a suspended state to a colloidal dispersion liquid comprising at least two of platinum, ruthenium and tin is sodium bisulfite,
The method for producing a fuel electrode catalyst for a liquid fuel cell according to claim 5, wherein the catalyst is any one of sodium hydrogencarbonate, sodium formate, sodium dithionate, sodium tartrate, sodium citrate, hydrazine, formalin and alcohol.