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A battery is a device that converts chemical energy to electrical energy.

A battery's chemical reactions involve the flow of electrons from one material (electrode) to another via an external circuit.

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A fuel cell is a device that uses a chemical reaction to generate electricity.

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• The oxidation and reduction reactions of an electrolyte with metals power a battery.

• When two dissimilar metallic substances, referred to as electrodes, are immersed in a diluted electrolyte, oxidation and reduction reactions occur in the electrodes, depending on the metal's electron affinity.

• The negative terminal of a battery is formed by the cathode, while the positive terminal is formed by the anode.

• When two dissimilar metals are immersed in an electrolyte, a potential difference between these metals is produced.

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An anode, a cathode, and an electrolyte membrane make up a fuel cell. A typical fuel cell functions by passing hydrogen through the anode and oxygen through the cathode. A catalyst at the anode site separates hydrogen molecules into electrons and protons. Protons pass through the porous electrolyte membrane, while electrons are forced through a circuit, resulting in an electric current and excess heat. Protons, electrons, and oxygen combine at the cathode to form water molecules. Fuel cells operate silently and with high reliability because there are no moving parts.

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The capacity of this system is greater than that of the zinc/carbon cell. It performs admirably at high discharge rates, continuous discharge, and low temperatures.

The following half-cell reactions take place inside the cell:

At the anode:  Zn + 2OH– → Zn(OH)₂ + 2e–
Zn(OH)₂ + 2OH– → [Zn(OH)₄]2–

At the cathode: 2MnO₂ + H₂O + 2e– → Mn₂O₃ + 2OH–
For full discharge: MnO₂ + 2H₂O + 2e– → Mn(OH)₂ + 2OH–

Overall: Zn + 2MnO₂ → ZnO + Mn₂O₃
For full discharge: Zn + MnO₂ + 2H₂O → Mn(OH)₂+ Zn(OH)2

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The zinc/carbon cell employs a zinc anode and a manganese dioxide cathode; carbon is added to the cathode to increase conductivity and retain moisture; the manganese dioxide, not the carbon, participates in the reaction.

The overall reaction in the cell is:

Zn + 2MnO₂ → ZnO + Mn₂O3

The exact mechanism for this is complicated, and there is still controversy over the exact mechanism, however the approximate half-cell reactions are:

Anode: Zn → Zn²⁺ + 2e–

Cathode: 2NH₄⁺ + 2MnO₂ + 2e– → Mn₂O₃ + H₂O + 2NH3

However, this is complicated by the fact that the ammonium ion produces 2 gaseous products:

2NH⁴⁺ + 2e– → 2NH₃ + H2

These products must be absorbed in order to prevent build up of pressure in the vessel. This occurs by 2 mechanisms:

ZnCl₂ + 2NH₃ → Zn(NH₃)₂Cl2

2MnO₂ + H₂ → Mn₂O₃ + H₂O

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Department of Materials Science and Metallurgy - University of Cambridge. (n.d.). • zinc/carbon batteries. Retrieved October 31, 2021, from https://www.doitpoms.ac.uk/tlplib/batteries/batteries_zn_c.php.

Fuel Cell Basics. Fuel Cell & Hydrogen Energy Association. (n.d.). Retrieved October 31, 2021, from https://www.fchea.org/fuelcells?fbclid=IwAR2yIP1eNqJnOdbmLBp_t7BWa0eVmoNscyoPs88rJLQusavsmsTLPbhDGiU.

Fuel Cell Store. (n.d.). Retrieved October 31, 2021, from https://www.fuelcellstore.com/.

Madhu. (2019, October 4). Difference between fuel cell and Battery. Compare the Difference Between Similar Terms. Retrieved October 31, 2021, from https://www.differencebetween.com/difference-between-fuel-cell-and-battery/#Fuel%20Cell%20vs%20Battery%20in%20Tabular%20Form.

Mischa. (2018, March 5). How A battery works. Curious. Retrieved October 31, 2021, from https://www.science.org.au/curious/technology-future/batteries?fbclid=IwAR3wDLAznrpK2hoe6YASGDpcetz7BzA6xvA9A-fZCZlGZjNvbSygf84I7xs.

Wikimedia Foundation. (2021, October 28). Solid oxide fuel cell. Wikipedia. Retrieved October 31, 2021, from https://en.wikipedia.org/wiki/Solid_oxide_fuel_cell.

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REDOX REACTIONS

Anode: 2H₂ (g) + 4(OH)- (aq) → 4H₂O (l) + 4e-

Cathode: O₂ (g) + 2H₂O (l)+ 4e- → 4(OH)-(aq)

Overall: 2H₂ (g) + O₂ (g) → 2H₂O (l)

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Anode reaction: 2H₂ + 2O2− → 2H₂O + 4e−

Cathode reaction: O₂ + 4e− → 2O2−

Overall cell reaction: 2H₂ + O₂ → 2H₂O

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Battery — produces electrical energy for a relatively short period of time.
Fuel Cell — can provide us with electrical energy for an extended period of time.

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Battery  — contains a limited amount of fuel and oxidant, and these two components degrade over time, so this device cannot provide electrical energy for an extended period of time.
Fuel Cell — Constantly supplied with fuel and oxygen from an external source, allowing it to operate for an extended period of time.

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Both are used as backup power sources when utilities are unavailable.

When the generator is turned on, both supply electricity.