A team, including scientists from University of California, Santa Barbara, USA and Indian Institute of Technology -Kanpur, have developed a new technique to reduce the amount of carbon dioxide produced while making hydrogen. The new method not only reduces the amount of greenhouse gases, but also allows for the reuse of carbon that is produced in the reaction.
Hydrogen fuel cells are hailed as the best alternative to fossil fuels, packing more energy than the latter and being much cleaner, as the only byproduct produced is water. Large scale production and storage of hydrogen, however, remains a challenge with research in the area very active.
In the new study, the scientists wanted to reduce the amount of carbon dioxide produced while making hydrogen through methane pyrolysis. Conventionally, a process called steam reformation of methane, where high temperature steam reacts with methane to produce hydrogen, in the presence of a solid catalyst, has been employed to produce hydrogen. The high temperature reaction also releases carbon dioxide- a greenhouse gas, which in turn reacts with the solid catalyst. Over time, the carbon deposited over the solid catalyst renders it inactive, requiring a change of the catalyst.
For their new method, the scientists replaced the solid catalyst with a mixture of active catalysts of methane, like nickel, palladium and platinum, and low-melting temperature metals, like indium, gallium, and tin. The mixture produces a molten metal alloy which can act as a catalyst for the pyrolysis of methane into hydrogen and carbon. Unlike conventional methods, the molten metal alloy allows the insoluble carbon produced during the methane pyrolysis, to float up through the alloy to form a layer at the top that can be skimmed off. Once removed, the carbon can be stored or incorporated into composite materials. As the carbon floats to the surface and does not stick to the catalyst, the catalyst does not get deactivated over time, avoiding replacement of the catalyst. The new method allowed for a conversion of 95% of the methane into pure hydrogen, with no carbon dioxide or other by-products, providing a cleaner way of producing the clean energy source- hydrogen.