Turquoise hydrogen (and CNTs) - What is it?

I went to a talk this week by Professor Boies of the Department of Engineering, who was presenting on his group's research on Turquoise hydrogen. The title of the talk caught my eye because I had not heard of “Turquoise hydrogen” before. I had heard of blue hydrogen and green hydrogen, but not turquoise. It turns out, it is called turquoise hydrogen because, unlike blue hydrogen production, which produces CO₂, turquoise hydrogen production produces carbon. It is therefore more green, and green and blue make turquoise.

In the Boies research group, the team is working on the pyrolysis of methane gas to hydrogen and carbon nanotubes (CNTs). The driver for the work is to produce hydrogen (fuel), alongside a valuable carbon material. Currently, the CNTs produced can be used in batteries for example, but in the longer term, as their mechanical performance is improved, it is hoped they could be used as construction materials to replace steel, for example.

The basic reaction is pyrolysis of methane (CH₄) to hydrogen and carbon, but the “magic” which happens in the floating particle catalysed process, leads to the self-assembly of long CNTs which critically then undergo collisions and form “clusters” towards the exit of the furnace. These clusters can then be wound into fibres or mats.  As a chemist, I find it quite remarkable that these highly-ordered structures self-assemble in temperatures exceeding 1000°C, so the idea that these can then be aligned to form fibres which are pulled out the furnace amazes me. 

The research team has already established that the size of the particle catalysts is critical to the production of CNTs instead of soot, and Professor Boies speculated that if his team can improve their control of this aspect of the process, both catalyst efficiency and reactor yields will improve. Projecting forwards, he thought that combining such modifications with improved drawing techniques - possibly inspired by the polymer sector - materials suitable to replace steel might be possible in the not-too-distant future.

The appeal of the process in our drive to sustainability is self-evident. Use landfill gas. Make hydrogen fuel, without CO₂ production. Make valuable carbon products that replace steel, thereby avoiding further CO₂ production.