Electrolysis of Water
2H2O → 2H2 + O2
Overview
An electric current passed through water splits it into hydrogen gas at the cathode and oxygen gas at the anode. The minimum voltage required is 1.23 V (thermodynamic), but practical electrolyzers operate at 1.8–2.0 V due to overpotential. A small amount of electrolyte (acid, base, or salt) is needed to make water conductive.
Participants
| Role | Substance | Coefficient | State |
|---|---|---|---|
| Reactant | Water H₂O | 2 | (l) |
Everyday Example
Green hydrogen production uses renewable electricity to electrolyze water, producing clean fuel for vehicles and industry.
Industrial Importance
Water electrolysis produces about 4% of the world's hydrogen. Green hydrogen from electrolysis is projected to reach $1.5/kg by 2030.
Properties
- Type
- Electrochemical
- Reversible
- Yes
- Energy
- Endothermic
- ΔH
- 572.0 kJ/mol
Related Reactions
Alkaline Battery Discharge
Anodizing of Aluminum
Cathodic Protection (Zinc Sacrificial Anode)
Chlor-Alkali Electrolysis
Chrome Electroplating
Copper Electroplating
Daniell Cell (Zinc-Copper Galvanic Cell)
Electrochemical CO₂ Reduction to CO
Electrochemical Machining (ECM)
Electrolysis of Molten NaCl (Downs Process)
Frequently Asked Questions
What is the equation for Electrolysis of Water?
The balanced equation is: 2H₂O → 2H₂ + O₂.
What type of reaction is Electrolysis of Water?
Electrolysis of Water is a electrochemical reaction. It is reversible under certain conditions.
Is Electrolysis of Water exothermic or endothermic?
Electrolysis of Water is endothermic (absorbs energy). The enthalpy change (ΔH) is 572.0 kJ/mol.