The magic of water electrolysis

In the quest for clean, sustainable energy sources, scientists and engineers have turned their attention to one of the most abundant substances on Earth: water.

Through a process as close to modern alchemy as we get, they’re transforming water (H₂O) into hydrogen gas (H₂), a clean fuel that could power our cars, heat our homes, and even generate electricity. This transformative process is known as water electrolysis, and it’s at the forefront of the clean energy revolution.

The magic of water electrolysis

Water is composed of two elements: hydrogen and oxygen. Imagine splitting water into its basic components, hydrogen gas (H₂) and oxygen gas (O₂), as shown in the diagram below.

Split water into hydrogen gas and oxygen gas.
Split water into hydrogen gas and oxygen gas.

Hydrogen is reduced once it gains electrons, while oxygen is oxidized it loses electrons. This process does not happen naturally. The electrical energy from a battery can force this process to happen.

Shortly after the invention of the battery by Alessandro Volta in the early 19th century, the technique of water electrolysis was developed by William Nicholson and Sir Anthony Carlisle. They performed the first recorded electrolysis by immersing two wires connected to a battery into water, observing the generation of hydrogen and oxygen gasses, as shown in the diagram below.

Water electrolysis generates hydrogen gas and oxygen gas
Water electrolysis generates hydrogen gas and oxygen gas.

Water electrolysis is a simple process. When electricity flows through the water from one electrode to the other, it breaks the bonds between hydrogen and oxygen atoms. Hydrogen bubbles up at one electrode (the cathode), and oxygen at the other (the anode). Since pure water has a low conductivity, NaOH or sulfuric acid is added to water to increase conductivity and electrolysis efficiency.

Green hydrogen

The true magic of water electrolysis lies in its ability to produce “green” hydrogen. When the electricity used in the process comes from renewable sources like wind, solar, or hydroelectric power, the hydrogen produced is virtually free of carbon emissions. This “green” hydrogen represents a clean, sustainable fuel option that emits only water when used in a fuel cell or burned.

Types of water electrolyzers

Alkaline water electrolyzers

The discovery of the fundamental principles of water electrolysis by William Nicholson and Sir Anthony Carlisle marked the inception of alkaline electrolysis as a method for hydrogen production. By 1900, by leveraging low-cost hydroelectricity, over 400 industrial alkaline electrolyzers were in operation mainly for ammonia production in the fertilizer industry.

Modern alkaline water electrolyzers have evolved significantly with recent advancements focusing on improving efficiency, reducing costs, and enabling the integration with renewable energy, such as solar cells and wind turbines.

Proton exchange membrane water electrolyzer

The development of proton exchange membrane (PEM) electrolysis began in the 1960s at General Electric, utilizing an acidic fluorinated ionomer as a solid electrolyte. This technology was initially developed to overcome the limitations of alkaline electrolyzers, such as low current density and low-pressure operation issues.

PEM electrolyzers feature a solid polymer electrolyte that ensures the separation of product gasses and electrical insulation of the electrodes. PEM electrolyzers offer several advantages, such as fast dynamic response times, large operational ranges, and high efficiencies. This makes it a promising technology for green hydrogen production powered by renewable energy of solar cells and wind turbines.

Solid oxide electrolyzer cells

Solid oxide electrolyzer cells (SOECs) were also developed around the same time as PEM electrolyzers. General Electric and the Brookhaven National Laboratory started developing high-temperature electrolysis with solid oxide cells in the late 1960s.

SOECs are a class of high-temperature electrolysis technology that uses solid ceramic materials as the electrolyte for the electrolysis of water to produce hydrogen at high temperatures (typically between 700 ºC and 900 ºC). The high operating temperature of SOECs enables the use of steam instead of liquid water, which significantly improves the thermodynamic efficiency of the hydrogen production process.

Emerging water electrolyzers

The above described alkaline water electrolysis, proton exchange membrane electrolysis, and solid oxide electrolyzer cells are traditional electrolysis technologies. However, recent innovations have introduced new types of electrolyzers that promise higher efficiencies and potentially lower costs.

  • Anion exchange membrane water electrolyzer

Anion exchange membrane (AEM) electrolyzers are a relatively recent development in the field of water electrolysis. AEM electrolyzers combine the benefits of traditional alkaline electrolyzers and PEM electrolyzers, utilizing a semipermeable membrane that conducts hydroxide ions. The development of AEM technology is ongoing, with significant advancements and interest in the field.

  • Hysata’s capillary water electrolyzers

One of the most notable recent developments in electrolyzer technology is Hysata’s capillary water electrolyzer. The hydrogen- and oxygen-evolving electrodes come into contact with water via capillary-induced transport along a porous inter-electrode separator, resulting in bubble-free operation at the electrodes.

The electrolysis cell has a 98% energy efficiency for water electrolysis, which is superior to commercial electrolysis cells. It consumes significantly less energy (40.4 kWh/kg hydrogen) than commercial electrolysis cells (47.5 kWh/kg hydrogen). High energy efficiency and the promise of a simplified balance-of-plant bring cost-competitive renewable hydrogen closer to reality.

You can check out our research on Hysata’s capillary water electrolysis technology in detail.

  • H2Pro membrane-free electrolyzers

Another groundbreaking development is H2Pro’s water electrolyzer that produces hydrogen and oxygen in separate chambers without the need for a membrane. This design addresses one of the key challenges in traditional electrolysis methods, where the membrane can be a source of inefficiency and increased costs.

H2Pro’s water-splitting method replaces the conventional water oxidation reaction in the anode of an alkaline electrolyzer with a two-step cycle: the anode is first charged (electrochemically) and then regenerated (chemically). In traditional alkaline electrolyzers, the production of hydrogen at the cathode is accompanied by the production of oxygen at the anode.

H2Pro’s new water splitter could significantly reduce the cost of green hydrogen production.

You can check out our research on H2Pro’s membrane-free water electrolysis technology in detail.

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