» 水的电解

水的电解

1800-05-02
  • William Nicholson
  • Anthony Carlisle
演示水分解成氢气和氧气的电解装置。

(generate image for illustration only)

水的电解是通过电流通过水(H₂O)分解成其组成元素氧气(O₂)和氢气(H₂)。在阴极,两个水分子被还原形成氢气和氢氧根离子。在阳极,两个水分子被氧化形成氧气、质子和电子。

The decomposition of pure water into hydrogen and oxygen is a thermodynamically unfavorable process, requiring external energy in the form of electricity. Pure water is a poor conductor of electricity, so an electrolyte, such as a small amount of a soluble salt or an acid like sulfuric acid, is typically added to increase conductivity. The overall balanced equation for the reaction is [latex]2H_2O(l) \rightarrow 2H_2(g) + O_2(g)[/latex].

The process occurs in an electrolytic cell. At the negatively charged cathode, a reduction reaction takes place: [latex]2H_2O(l) + 2e^- \rightarrow H_2(g) + 2OH^-(aq)[/latex]. At the positively charged anode, an oxidation reaction occurs: [latex]2H_2O(l) \rightarrow O_2(g) + 4H^+(aq) + 4e^-[/latex]. The production of hydrogen gas at the cathode is exactly twice the volume of oxygen gas produced at the anode, a direct consequence of the stoichiometry of water. This 2:1 volume ratio is a classic demonstration in chemistry classrooms, often performed using a Hofmann voltameter.

The minimum voltage required for electrolysis to occur, known as the decomposition potential, is 1.23 V at standard conditions. However, in practice, a higher voltage, called 过电位, is needed to overcome various activation barriers. The efficiency of water electrolysis is a key factor in the viability of a hydrogen-based economy, with significant research focused on developing more effective and cheaper catalysts for the anode and cathode to reduce the overpotential and energy consumption.

UNESCO Nomenclature: 2406
- 电化学

类型

化学工艺

中断

实质性

使用方法

广泛使用

前体

  • 亨利·卡文迪什发现氢
  • 卡尔·威廉·舍勒和约瑟夫·普里斯特利发现氧气
  • invention of the voltaic pile by alessandro volta

应用

  • 用于燃料电池和汽车的氢气生产
  • 生产用于医疗和工业用途的高纯度氧气
  • 潜艇和航天器中的生命支持系统
  • 焊接和切割炬(氢氧)
  • 氘(重水)的生产

专利:

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Related to: water electrolysis, hydrogen production, oxygen production, decomposition, cathode, anode, hofmann voltameter, green hydrogen.

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