How to write the negative electrode reaction equation for a fuel cell

There are many kinds of fuel cells, and the topic is what to say.

Methane fuel cell molten carbonate electrode reaction formula: CH4 + 2O2 = CO2 + 2H2O. Methane fuel cells are redox batteries in chemical cells.

A fuel cell is a chemical power source in which the fuel and oxidizer (usually oxygen) participate in the galvanic cell reaction near the electrode.

These positive and negative electrode reactions are superimposed, and the total reaction of hydrogen and oxygen fuel cell is 2H2+O2=2H2O.

The principle of hydrogen-oxygen fuel cell reaction, which is the inverse process of electrolysis of water.

The electrode should be: negative electrode: h +2oh 2h o+2e positive electrode: 1 2o +h o+2e 2oh battery reaction: h +1 2o ==h o.

[Tip 1] The negative electrode reaction of a fuel cell is generally more difficult to write, while the positive electrode reaction and the total battery reaction are easier to write. Subtract the positive reaction from the total reaction of the battery to obtain the negative reaction, which is an ingenious way to write the negative reaction formula.

The total ion reaction formula of methane fuel cell is: CH4+

2oh-+2o2=

co+3h2o

The positive reaction formula is: O2+2H2O

4e-4oh- so the negative reaction formula should be: -2

That is, CH4+

10oh--8e-

CO+7H2O [Tip 2] According to the conservation of electrons gained and lost, the conservation of atoms, and the conservation of charge, the more complex negative electrode reaction formula is directly written.

In the negative electrode, methane is oxidized to carbon dioxide, which cannot exist in alkaline conditions, and combines hydroxide to form carbonate. The valency of carbon in methane increases from -4 valence to +4 valence in carbonate, so 1

mol methane loses 8

mol electrons, combined with OH- to generate 1

molco, and then according to the conservation of charge, the electrode reacts to the right side of co

4 cases of hydrogen and oxygen fuel cells:

1. If the electrolyte is an acid solution

1. The negative electrode reaction formula is: 2H2-4E-==4H+.

2. The positive electrode reaction formula is: O2 + 4H+ +4E ==2H2O.

2. If the electrolyte solution is an alkaline solution

1. The negative electrode reaction formula is: 2H2 + 4OH -4E ==4H20.

2. The positive electrode reaction formula is: O2 + 2H2O + 4E ==4OH.

Hydrogen-oxygen fuel cell property analysis:

1. The active substances (fuel and oxidizer) of the fuel cell are continuously input at the same time as the reaction, so this type of battery is actually just an energy conversion device.

2. This type of battery has the advantages of high conversion efficiency, large capacity, high specific energy, wide power range, and no need to charge, but due to the high cost, the system is more complex, and it is limited to some special purposes, such as spacecraft, submarines, military, TV transfer stations, lighthouses and buoys.

The above content reference: Encyclopedia - Hydrogen and oxygen fuel cells.

The cathode of a fuel cell is generally oxygen, such as a methane battery

Alkaline. Total reaction formula: CH4 + 2O2 + 2OH-=CO32-+3H2O cathode O2+4E-+H2O=4OH-

The negative electrode is actually the total reaction formula minus the positive electrode, i.e.

CH4-8E- -4H2O+2OH-=CO32-+3H2O-8OH- is equal to CH4-8E-+10OH-=CO32-+7H2O, acidity is to add one step OH-+H+=H2O

H+ is added before the equal sign and water is generated, and the product does not have OH-

1.Propane Fuel Cell:

Acidity. Negative electrode: C3H8 - 20E- +6H2O = 3CO2 + 20H+

Positive electrode: 5O2 +20E-+ 20H+ = 10H2O

Total cell reaction: C3H8 + 5O2 = 3CO2 + 4H2O

Basic: Negative: C3H8 - 20 E- +26OH- =3CO32- +17H2O

Positive electrode: 5O2 + 20 E- +10H2O = 20oh-

Total reaction: C3H8 + 5O2 + 6OH- =3CO32- +7H2O

Neutral: Negative: 5O2 + 20E-+10H2O = 20Oh-

Cathode: C3H8-20E-+6H2O=3CO2+20H+

Total reaction: C3H8 + 5O2 = 3CO2 + 4H2O

2.Methanol fuel cells:

Acidity: Negative electrode: 2CH3OH-12E-+2H2O=12H++2CO2

Cathode: 3O2+12E-+12H+=6H2O

Total reaction: 2CH3OH+3O2=2CO2+4H2O

Alkaline: negative electrode: 2CH3OH-12E-+16OH-=2CO32-+12H2O

Positive electrode: 3O2 + 12E-+6H2O = 12Oh-

Total reaction: 2CH3OH+3O2+4OH- =2CO32-+6H2O

Neutral: Negative: 2ch3oh-12e-+2h2o=12h++2CO2

Positive electrode: 3O2 + 12E-+6H2O = 12Oh-

Total reaction: 2CH3OH+3O2=2CO2+4H2O

3.[Writing of Fuel Cell Electrode Reactive Formula] is excerpted from "Innovative Design".

According to the characteristics of the fuel cell, the substances that generally undergo the reduction reaction on the positive electrode are O2, and the electrode reaction is different with the different electrolyte solutions

1) The positive electrode reaction formula in the environment of acidic electrolyte solution: O2 4H4E ==2H2O

2) The positive reaction formula in the alkaline electrolyte solution environment: O2 2H2O 4E ==4OH

3) Solid electrolyte (can conduct O2 at high temperature) in the environment of the positive electrode reaction formula: O2 4E ==2O2

4) Molten carbonate (e.g., molten K2CO3) in the cathode reaction formula: O2 2CO2 4e ==2CO32.

5) Write the negative reaction formula of the battery according to the total reaction formula and the positive reaction formula of the battery: negative reaction formula total reaction formula positive reaction formula.

Alkaline condition anode: 2CH3OH-12E 16OH 2CO32 12H2O

Acidic condition anode: 2CH3OH 12E 2H2O 12H2CO2

The working principle of fuel cells is the same, and the writing of their electrode reaction patterns is also regular. Writing the reaction formula of the fuel cell electrode is generally divided into three steps: the first step is to write the total reaction equation of the fuel cell; The second step is to write the positive reaction formula of the fuel cell; The third step is to write the negative electrode reaction formula of the fuel cell.

Such as: alkaline conditions. The total reaction formula is 2CH3OH + 3O2 + 4OH 2CO3 2 6H2O

Positive electrode: 3O2 + 12E-+6H2O = 12Oh-

Negative electrode: 2CH3OH 12E 16OH 2CO3 2 12H2O

Acidic conditions. Total reaction formula: 2CH3OH3O2 2CO2 4H2O

Cathode: 3O2+12E-+12H+=6H2O

Negative electrode: 2ch3oh 12e 2h2o 12h 2CO2

1. If the electrolyte solution is alkali or salt solution.

The negative electrode reaction formula is:

The positive reaction formula is:

2. If the Huiyu electrolyte solution is an acid solution.

The negative electrode reaction formula is:

The positive reaction formula is:

The total reaction equation is:

In alkaline solution, the OH content is extremely high, so the H+ generated at the negative electrode will directly combine with OH to form water, while the OH generated at the positive electrode will exist in the form of ions due to the lack of H+ binding. Acidic solutions are the opposite.