The suite of substances that can tackle carbon dioxide

One of the reasons carbon dioxide is such a problem is that it’s very difficult to break down: the bonds in CO₂ molecules are very stable, and it’s hard to find something that can slice them open.

But if we can develop compounds that do cut up these inert bonds, CO₂ and other molecules that hang around in our atmosphere, like nitrogen (N₂) and nitrogen oxides (NO_x) could become valuable green feedstocks for the global chemical industry.

This could help the notoriously polluting industry become carbon-negative.

A team of Chinese researchers has come up with a suite of catalysts that can help to demolish these inert bonds.

“The chemical industry has played a crucial role in society’s historical evolution, but it also presents emerging environmental concerns and skyrocketing CO₂ emissions,” says Professor Buxing Han, a researcher at the Chinese Academy of Sciences’ Institute of Chemistry, and corresponding author on a paper describing their catalysts, published in Industrial Chemistry & Materials.

“We were motivated to explore the possibilities of green chemistry and chemical engineering to transform renewable feedstocks, such as CO₂ and NO_x, into environmentally friendly chemicals, including syngas, hydrocarbons, oxygenates, and ammonia.”

The researchers looked at substances called multicomponent electrocatalysts: “electrocatalysts” prompt and speed up reactions with electricity, and those made of multiple components tend to be more stable and efficient than single-component catalysts.

“We wanted to explore electrochemical conversion as a universal carbon-neutral route to efficiently upgrade green chemical sources with inert bonds to chemicals and fuels under ambient conditions harnessing clean energy,” says co-corresponding author Professor Xiaofu Sun, also at the Chinese Academy of Sciences’ Institute of Chemistry.

“We developed three models for multicomponent catalysts: Type I, Type II, and Type III, which we discuss in our paper.”

Type I catalysts are made of a catalytic part, and another component that protects or activates it. Type II are made of several catalysts, which provide several steps for a reaction to take place. Type III have one component which is a substrate: something for the catalyst, and the inert molecules, to land on.

“Each of these models has its own advantages and disadvantages, depending on the specific reaction and catalyst,” says Han.

“We explored the use of these models in our paper to show their effectiveness in the electroreduction of small molecules.”

They also discuss where chemists should be investigating next, to get these catalysts from the lab into the chemical industry.

“One key challenge is improving the selectivity and efficiency of the electrocatalysts, as well as increasing their stability and activity,” says Sun.

Chemists also don’t know exactly how all these catalysts work yet, at a molecular level – just that they seem to work.

“More importantly, there is a need for further research and development to scale up and integrate these electrochemical processes into industrial applications. Many promising research projects are undergoing in our lab,” says Han.