Hydrogen is one of the most important ingredients in the chemical industry.
About a quarter of all chemical processes around the world include at least one step that involves hydrogen.
A key part of these reactions is splitting hydrogen gas (H₂) into more reactive forms that can then drive other chemical changes.
There are two main ways to split hydrogen. One is called homolytic dissociation, where the hydrogen molecule is evenly divided into two atoms.
The other, known as heterolytic dissociation, produces charged, polar hydrogen species. These polar forms are especially useful because they can selectively react with other polar molecules, making them essential for producing fine chemicals.
The problem is that heterolytic dissociation usually requires extreme conditions—high heat and high pressure. That makes the process energy-hungry, expensive, and sometimes risky.
Now, an international team led by Prof. Wang Feng from the Dalian Institute of Chemical Physics in China, working with Prof. Paolo Fornasiero from the University of Trieste in Italy, has found a way to make this process happen at normal room temperature using light.
The researchers used a special material: titanium dioxide coated with tiny particles of gold (Au/TiO₂).
When this material was exposed to ultraviolet (UV) light, electrons in the titanium dioxide moved toward the gold, while the “holes” they left behind were trapped at the interface between the gold and the titanium dioxide. This created pairs of charges right next to each other, which then provided the energy needed to split hydrogen heterolytically.
Tests showed that the reaction speed closely followed the intensity of the light, proving that the splitting was powered by the photocatalyst.
Even more impressively, the team used the activated hydrogen to reduce carbon dioxide (CO₂). Under UV light, the CO₂ was almost completely converted into ethane.
By adding a further step—removing hydrogen from ethane—they produced ethylene, a vital industrial chemical, with a yield above 99% for more than 1,500 hours.
The method isn’t limited to UV light. The team showed it also works with photocatalysts that respond to visible light, such as nitrogen-doped TiO₂ and other metal oxides. Using solar energy, they achieved an ethane selectivity as high as 90%.
This discovery points to a greener future for the chemical industry. By using light instead of heat and pressure, scientists could reduce both energy costs and carbon emissions, while still producing valuable chemicals like ethane and ethylene.
As Prof. Wang explained, the next step is to scale up the method so that it can be powered by sunlight and integrated into modern chemical production.
Source: Chinese Academy Sciences.
