The Wonder Cactus that Teaches How to Produce Green Hydrogen

The prickly pear cactus, capable of growing in arid and desolate areas with hardly any water, can be considered one of the most versatile cacti in the world. Both its edible fruits - prickly pears - and its stems, consumed in Mexican cuisine in nopal salads or with jalapeños, and its use for breeding chinchillas, preventing soil erosion, or producing biofuel, confirm this. What was not known until now is that it would inspire a new technique for more efficient production of green hydrogen. To this end, a group of scientists from the University of Texas has resorted to biomimicry, i.e., the development of technological solutions based on nature.   

A cactus for green hydrogen production

The production of green hydrogen, one of the most promising renewable energies for use in sustainable mobility in projects such as this one, is based on electrolysis. That is, the application of an electric current through electrodes immersed in water so that the oxygen and hydrogen molecules are separated. Finally, to be considered green, the electricity used in the process must also be of renewable origin. Generally, this process is somewhat less efficient than other solutions, such as photovoltaics or wind power, and requires catalysts such as platinum or iridium.

Right now, research is aimed at improving its efficiency so that it can compete on a level playing field with other renewable energies in the medium term. One of them is the proposal of the University of Texas, which has developed a low-cost material based on nickel. And the key lies in the prickly pear cactus. The team had been investigating the use of nickel in electrolysis for some time, as it is a material a thousand times cheaper than platinum. However, it is also much less efficient, so how to increase its efficiency in producing green hydrogen without increasing the cost of the process?

The eureka moment usually occurs after repeatedly contemplating something until it is observed with new eyes one day. Something like that happened to one of the researchers on the project who saw some nopales daily on his way to the lab. This cactus has some of the largest stems and berries in its genus, allowing it to trap atmospheric water with excellent efficiency. Perhaps, if a catalyst with a shape similar to that of the flat stems of the nopal cactus could be developed, the production of green hydrogen could be multiplied.

The team got to work and soon had the first 3D nanostructure model in the shape of cactus stems using nickel as raw material. And it seems they were right on target: the scientists have confirmed that the strategy has yielded positive results. They hope to develop a commercially viable system in the medium term.

The promoters of the project claim that green hydrogen can transform energy technologies without generating greenhouse gases and with a zero carbon footprint. In that sense, aviation is one of the industries with the most significant potential to benefit from this type of energy.  

Nopales as renewable energy plants

Besides the gastronomic or ecological applications of the nopal cactus mentioned earlier on, this plant has opened up unprecedented possibilities for the production of green power in a much more direct way than catalysts for the production of green hydrogen. In this case, the idea is to use the living cactus as an electricity generator.

Every plant generates a weak electrical current in its metabolic processes, but the large surface area of nopal stems makes it an ideal candidate for this approach. A recent study has demonstrated the optimal configuration for obtaining electricity with copper and zinc electrodes inserted into nopal stems.

The experiment results indicate that up to 58.8 mW can be obtained by eighteen pairs of electrodes inserted into six cactus stems, optimized with series and parallel connections. This current is enough to power an LED light or a calculator, or keep basic IoT sensors operational.

If, besides the production of green hydrogen or the use of nopales as power plants, you want to know more about the electricity of small things, you can read this article which explores TENGs, i.e., triboelectric nanogenerators that generate energy through vibrations. And, of course, subscribe to our newsletter at the bottom of this page.  

Sources:

• Taylor & Francis
• TechXplore