Chinese researchers have developed a new catalyst for seawater electrolysis that maintained high efficiency for over 7,000 hours of continuous operation. This technology could significantly simplify the process of producing hydrogen from seawater.

Hydrogen as an Energy Source

Hydrogen is considered a promising source of clean energy. When used as fuel, the only byproduct of its reaction is water. Hydrogen itself can be obtained from water through electrolysis, a process in which water molecules are split into hydrogen and oxygen under the influence of electric current.

Challenges of Traditional Electrolysis

Conventional electrolysis requires fresh water, which is a limited resource. Therefore, using seawater, which is available in much larger quantities, has been proposed. However, before electrolysis, seawater is usually desalinated, increasing both the cost and complexity of the process. Direct electrolysis of seawater faces several challenges, including the corrosive effects of chloride ions (Cl−).

A New Solution from Chinese Scientists

Researchers from the South China University of Technology discovered that small amounts of chloride ions can not only be harmless but may also help restructure the catalyst, enhancing its efficiency. The results of their work were published in the journal Nature Communications.

Features of the New Catalyst

Catalysts are used to accelerate the relatively slow process of splitting water into hydrogen and oxygen. The new NiFe-MOF-S catalyst consists of nickel disulfide (NiS2) nanoparticles deposited on nanosheets of a nickel-iron-based metal-organic framework (NiFe-MOF). This design allows precise control over the positioning of chloride ions relative to the catalyst's active sites.

Testing and Efficiency

The NiFe-MOF-S catalyst was tested in alkaline seawater, which was made alkaline by adding potassium hydroxide. To achieve a current density of 500 milliamperes per square centimeter, only 213 millivolts of additional voltage were required—lower than in a standard potassium hydroxide solution (268 millivolts).

The catalyst demonstrated not only high efficiency but also durability: it operated for more than 7,000 hours in alkaline seawater at a current density of 1 ampere per square centimeter, with the overpotential increasing by just 1.4 microvolts per hour.

Industrial Testing

An electrolyzer equipped with the new catalyst was also tested under conditions close to industrial settings. In these conditions, the device operated stably for over 1,500 hours.