To break the bonds between hydrogen molecules, researchers used gold, titanium, and ultraviolet radiation. The resulting hydrogen was then used to convert carbon dioxide into ethylene.

The Importance of Hydrogenation in Industry

Hydrogenation—the reaction of adding hydrogen to organic compounds—plays a crucial role in the chemical industry. This process is used to produce fuels, plastics, detergents, alcohols, thickeners, and stabilizers for the food industry from petroleum.

Catalysts and Mechanisms of Hydrogen Dissociation

To carry out the hydrogenation reaction, it is necessary to split molecular hydrogen (H₂) into individual atoms—a step known as dissociation. There are two main mechanisms: homolytic and heterolytic dissociation. Catalysts, often rare and expensive metals such as gold, copper, platinum, and palladium, are used to accelerate these reactions.

Heterolytic dissociation typically requires high temperatures and pressures, resulting in the formation of positively and negatively charged hydrogen ions. Homolytic dissociation leads to the creation of two neutral hydrogen atoms. For industrial purposes, the homolytic pathway is preferred because it produces "active" hydrogen, which more readily participates in reactions. However, this process is energy-intensive and poses safety risks due to the high temperatures involved.

A New Approach to Hydrogen Dissociation

Researchers have proposed an innovative strategy for the heterolytic dissociation of H₂. As a catalyst, they used titanium dioxide with gold nanoparticles (Au/TiO₂) and irradiated the system with ultraviolet light at a wavelength of 365 nanometers. This approach enabled hydrogen to be split at room temperature. The results of the study were published in the journal Science.

The Mechanism of Photochemical Dissociation

The article provides a detailed description of the mechanism behind the photochemical dissociation of hydrogen. Under ultraviolet light, electrons move from TiO₂ to the gold nanoparticles, while holes are captured by defects at the interface formed by Au–O–Ti structures. The electrons are positioned close to both the gold and the holes, forming electron-hole pairs that stimulate the breaking of bonds between hydrogen atoms.

Results and Application Prospects

The scientists found that the activity of H₂ dissociation is almost linearly dependent on the intensity of ultraviolet radiation, confirming the role of light as a catalyst for the reaction at room temperature.

The developed process made it possible to reduce inert carbon dioxide (CO₂) to ethane at room temperature, and subsequent photocatalytic dehydrogenation of ethane led to the formation of ethylene. The reaction efficiency exceeded 99% after 1,500 hours of UV irradiation. The method also worked successfully under sunlight, as the necessary ultraviolet wavelength is present in the solar spectrum.

These results offer hope that the proposed method will be in demand not only in scientific research but also in industry. Scientists see the potential to scale up this strategy into a technology that uses sunlight or photothermal radiation to modernize chemical manufacturing.