Putting catalytic chemistry at the heart of the green energy transition
Plasma is considered the fourth state of matter(opens in new window) after solid, liquid and gas. It comprises a superheated gas where atoms are split into free electrons and positive ions. By rapidly pulsing (modulating) the power input on a nanosecond-to-microsecond scale, the production of these high-energy electrons can be precisely controlled. In addition, the surrounding gas molecules are kept cool, maximising chemical and energy efficiency. This advanced method of electrical excitation, known as fast-modulated plasma, can generate cold plasma or non-thermal plasma (NTP)(opens in new window) processes. These can be used for the chemical conversion of small, low reactive molecules such as carbon dioxide, diatomic nitrogen, methane and water under near ambient temperatures and pressures. However, a catalyst is required to control these reactions and selectively produce the desired compounds. But this requires a fresh approach as the catalyst can also halt the reaction of the plasma-activated molecules rather than working together with them.
Lower environmental impact
The ERC-funded SCOPE(opens in new window) project addressed this challenge by studying, modelling and applying the synergistic interaction between NTP and solid catalysts interacting. This combination creates an effect that is greater than the sum of their individual effects. The advantage of NTP processes is that they allow operations under very mild conditions when compared to conventional thermal catalytic processes. The technology is also well suited for coupling with renewable energy and thus for the electrification of chemical processes. The SCOPE project used NTP, which has a much lower carbon footprint (up to over 90 %), in three major industrial reactions. These were nitrogen fixation, methane valorisation to produce longer carbon-chain hydrocarbons and conversion of carbon dioxide to liquid solar fuels. “We have developed, for example, new processes to produce fertilisers in a distributed manner from atmospheric nitrogen,” says project coordinator Gabriele Centi, based at the University of Messina(opens in new window), Italy. “Synthetic fertilisers are essential for global food security, providing the nitrogen required to grow food for nearly half the world.”
Widely applicable across industries
Although SCOPE focused on improving large-scale chemical processes, the specific technology has applications far beyond the chemical industry. “Cold plasma is incredibly versatile and can contribute to more sustainable manufacturing, agriculture, healthcare, environmental protection, and even the food industry,” observes Centi. In agriculture, for example, cold plasma can be used to treat seeds before planting. “This chemical-free process improves water absorption, increases germination rates and promotes stronger early plant growth, helping farmers increase crop yields while reducing the need for chemical treatments,” adds Centi. Meanwhile, in the wood industry, plasma treatment makes timber surfaces more receptive to protective coatings. “As a result, manufacturers can achieve the same level of protection while using significantly less coating material, reducing both costs and environmental impact,” Centi continues.
A bright future
Plasma also has a place in food production, influencing crystal formation in materials such as chocolate to produce a product with a better shine, texture and the characteristic ‘snap’ consumers expect. This can now be achieved in a matter of minutes, rather than the hours required by conventional tempering methods. Similar approaches are being explored for sterilising medical equipment, developing new materials, cleaning polluted air and water(opens in new window), and improving energy-efficient manufacturing. “What makes cold plasma particularly exciting is that it enables many of these processes to be carried out with lower energy consumption and fewer chemicals, making it an important technology for a more sustainable future,” Centi concludes.
