Researchers at the Huazhong University of Science and Technology (HUST) in Wuhan, China, have found a reliable way to fix carbon dioxide gas from the atmosphere into useful chemical products, which scientists call a 'milestone' achievement, the South China Morning Post reported.

As the world looks to clean up the planet's warming carbon dioxide gas from the atmosphere, multiple approaches are being tested in laboratories where the gas can be converted into useful products such as methanol, ethanol, alkanes, or olefins. However, the approach to such conversion systems has a big drawback. They can only work for a hundred hours, making them unsuitable for large-scale operations. 

Why can conversion systems only run for a short time?

Scientists use electrochemical methods in these conversion systems, where an electric charge is applied to change a chemical's properties. For instance, the process involves breaking the chemical bonds between carbon dioxide molecules and adding elements like hydrogen to the mix to produce hydrocarbons such as ethanols or formic acid.

The process is carried out in the presence of an electrolyte where researchers have conventionally an alkaline feedstock. However, the process produces unwanted byproducts, such as carbonates, that attach themselves to the equipment, reducing efficiency. This has limited the lab equipment's lifetime to a few hundred hours.

The researchers at HUST teamed up with those from the University of Auckland, New Zealand. They spent the last five years looking for a viable solution to this problem. Their efforts yielded results when they found an electrolyte that could run the systems for at least 5,000 hours, longer than any known approach so far, marking a significant milestone. When calculated, efficiency of the system was recorded at 93%. 

Putting lead-acid batteries to use

Interestingly, the electrolytes used by the researchers came from spent lead acid batteries that were already looking for a safe method for their disposal. Used extensively in the automotive, energy, and military sectors, lead-acid batteries are a mature technology but have failed to work out simple processes for their disposal. 

Spent lead-acid batteries must be incinerated first before lead ions can be extracted. While lead is a toxic heavy metal, it is also very efficient in converting carbon dioxide. The researchers were looking to use the acidic environments of the batteries to carry out their electrochemical processes. Still, they found that the process was unstable in the environment and corroded the catalysts used.

The researchers then developed a suitable catalyst that was less corrosion-resistant and could accelerate the chemical reactions. The development of such a system allows spent lead acid batteries to be used more productively.

In their demonstration, the research team produced formic acid using carbon dioxide. The chemical has multiple applications in the agricultural sector but can also be used in fuel cells in the future. With further research, the team is confident that it will be able to produce products such as ethylene, referred to as the world's most important chemical, as it has applications in the textile, car, and printing industries.

The team also hopes that its technology will help fossil fuel industries decarbonise their operations, the report added.