I have been engaged in the electrode sheet industry for a period of time. If you want to have a better understanding of the industry, some of the electrode principles you need to understand are as follows:

  1. Follow the conservation of mass, electron and charge. In addition, it also follows: the principle of additivity: the reaction formula of the two electrodes is added together, and the total reaction formula of the battery is obtained after the electron is eliminated. Using this principle, the total reaction equation of the battery is subtracted from the known one electrode reaction equation to obtain the other electrode reaction equation. Coexistence principle: CO2 cannot exist in the alkaline solution, and there will be no H+ participating in the reaction or formation; in the same acid solution, there will be no OH-participating in the reaction or formation. According to this principle, matter has different forms in different media environments after gaining and losing electrons.

   Tips for writing electrode reactions

2. Accurately judge the two electrodes

example 1. Connect the zinc and aluminum sheets with wires, insert them into dilute sulfuric acid and concentrated sulfuric acid respectively, and write the electrode reaction formula and battery reaction formula of the two primary batteries.

Analysis: When dilute sulfuric acid is used as an electrolyte solution, the more active aluminum is oxidized, and hydrogen is released from the zinc flakes, so: negative electrode (aluminum flake): 2Al—6e—==2Al3+ positive electrode (zinc flake): 6H+ +6e—==3H2↑

Battery reaction: 2Al +6H+ == 2Al3+ +3H2↑

When concentrated sulfuric acid is used as an electrolyte solution, because aluminum is passivated in concentrated sulfuric acid at room temperature, and zinc can react with concentrated sulfuric acid, zinc flakes are used as negative electrodes and aluminum flakes are used as positive electrodes:

Negative electrode (zinc sheet): Zn—2e—==Zn2+ Positive electrode (aluminum sheet): 4H++SO42—+ 2e—==SO2↑+ 2H2O

Battery reaction: Zn+2H2SO4 (concentrated)==ZnSO4+ SO2↑+ 2H2O

2. Pay attention to the use of battery total reaction formula

example. Insert the platinum wire into the KOH solution as an electrode, and then pass methane and oxygen to the two electrodes respectively to form a galvanic cell. Then one pole of methane is passed into the ______ pole of the battery, and the reaction formula of this pole is _____________.

Analysis: The oxidation-reduction reaction of methane combustion is: CH4+2O2 == CO2+ 2H2O. It is impossible to release CO2 in alkaline solution: CO2+2OH—==CO32—+3H2O, so the total reaction formula of the battery is: CH4 +2O2 +2OH—==CO32— +3H2O. Oxidation occurs at one pole of methane flow, so it is the negative pole. The positive electrode absorbs oxygen, which can be regarded as oxygen-absorbing corrosion: 2O2+ 4H2O+8e— == 8OH—, the total reaction minus the positive electrode reaction to obtain the negative electrode reaction: CH4+10OH——8e—== CO32—+7H2O

4. Pay attention to the acidity and alkalinity of electrolyte solution

example. The hydrogen-oxygen fuel cell used on the American Apollo spacecraft is a new type of chemical power source.

⑴Using KOH as the electrolyte solution, the water produced by the electrode reaction can be used as drinking water for astronauts after being condensed. The reaction is: 2H2+O2==2H2O, and the electrode reaction formula is ___________;

⑵If KOH is changed to dilute H2SO4 as conductive material, the electrode reaction formula is ___________.

Analysis: In the application battery, the electrolyte participates in the electrode reaction, but only acts as a bridge during the entire reaction process. For example, an acidic electrolyte, H+ participates in one electrode reaction, but the other electrode reaction must generate H+, and at the same time, OH-; alkali Sex electrolytes have a similar situation

Answer: ⑴Negative pole: 2H2—4e—==4H+, Positive pole: O2+4H++4e—==2H2O;

⑵Negative pole: 2H2+4OH——4e—==4H2O, positive pole: O2+2H2O+4e—==4OH—.

4. The number of electrons transferred cannot be ignored

In the same primary battery, the number of electrons lost by the negative electrode must be equal to the number of electrons obtained by the positive electrode. Therefore, when writing the electrode reaction formula, pay attention to the conservation of charge. In this way, errors caused by rewriting the total reaction formula to the electrode reaction formula can be avoided, and errors in related calculations can be avoided at the same time.

  The above is the description of some technical methods of the electrode, I hope it can be helpful to the industry beginners.