•Notícia

Researchers from the Technical University of Catalonia (UPC) and the Scientific Research Council (CSIC) have developed and patented a catalyst for obtaining hydrogen from ethanol that may provide a definitive solution for vehicles that run on hydrogen.

It consists of a ceramic component with inside channels that are coated in an aerogel, a highly porous and transparent material that contains cobalt nanoparticles. These nanoparticles react to turn ethanol into hydrogen.

In order to work, the catalyst must be heated to its reaction temperature (around 310 ºC). A mixture of ethanol and water, in the form of a gas, then passes through the channels in the ceramic component and comes out as hydrogen and CO2. Six molecules of hydrogen and two of CO2 are obtained from every ethanol molecule and every three water molecules.

This device has great potential in the development of hydrogen fuel cells. The research directors, Jordi Llorca, a lecturer at UPC’s Institute of Energy Technology, and Elies Molins, a research fellow with the CSIC at the Materials Science Institute of Barcelona, have stated that one of the main advantages of the device is its energy-saving potential.

“The energy from each ethanol molecule corresponds to that from five hydrogen molecules”, explained Molins, CISC research fellow. “But in our catalyst, six hydrogen molecules are obtained as heat is absorbed during the reaction. Thus, advantage is taken of the residual heat from a fuel cell (or any other source), which results in improved overall performance of the system”. It is in fact a rechargeable circuit in which the energy needed to activate the catalyst is partly generated by the fuel cell itself.

Montserrat Domínguez and Elena Taboada, who are doctoral students at UPC and the CSIC, also took part in the research.

This catalyst could bring us closer to finding a definitive solution for hydrogen vehicles. There are currently over one hundred prototype motorcars that run on hydrogen, which is stored in high-pressure hydrogen tanks, and there are also a number of hydrogen filling stations. However, huge financial investments would have to be made to make the use of such vehicles widespread. Not only would all petrol-related infrastructures have to be replaced, money would also be needed to put safety measures in place (hydrogen is a highly inflammable, explosive gas).

This change to infrastructures could be avoided if vehicles had a device for generating hydrogen. Scientists from around the world have been pursuing this goal for many years, but so far none of the catalysts developed seemed viable.

The great advantage of this catalyst, which makes it more viable than any other designed to date, is that it does not need any prior treatment or to be protected from air contact or humid conditions. “All catalysts that have been the subject of research until now need a reduction treatment (a chemical process for reducing the degree of oxidation), which involved leaving the catalyst with hydrogen at high temperatures for a number of hours before each use”, explained Jordi Llorca, from UPC’s Institute of Energy Technology. In contrast, the catalyst developed at the CISC and UPC’s laboratories does not need to undergo induction or treatment and can be indefinitely reused in on-off cycles.

Other advantages are that the temperature required is far lower than that required by other catalysts and that hydrogen production is rapid: it is obtained in just two minutes. Furthermore, if ethanol fuel consumption is compared to the hypothetical consumption using this catalyst, performance is impressive: preliminary calculations show that fuel consumption could be reduced by about 25%.

From an environmental point of view, the catalyst will still produce CO2, although far less than vehicles that run on fossil fuels. In addition, the researchers are testing the device with synthetic fuels obtained from alternative sources (waste, for example). They are currently working with the business sector so that they can implement their design in real applications. Opportunities to do so could equally arise in the automobile sector and in relation to static energy generation systems, boilers, auxiliary generators and portable devices.

A lot still remains to be done to develop these applications, but a first giant step forward has been made to enable nanoparticles to be deposited in an aerogel on a commercial ceramic medium, which is in fact used in many industrial devices. The prototype is designed in such a way that it will just have to be scaled up or down to test the first applications.

In an ignition engine, 24.5 MJ (megajoules) of energy is obtained from every litre of ethanol, while a petrol engine yields 32.7 MJ. Using the catalyst developed by UPC and the CSIC, a litre of ethanol is tuned into 2.4 litres of hydrogen (in normal conditions), which can produce 24.8 MJ.

In terms of energy efficiency, the average performance of vehicles that run on hydrogen fuel cells is 36% on a journey in different cycles, according to the NEDC (New European Driving Cycle) standard. That is to say, of the 24.8 MJ of energy produced, 36% is converted into the effective movement of a car. According to the above NEDC standard, the performance of a vehicle with an ignition engine is 22%.

Furthermore, the greatest theoretical performance of a petrol engine is 37%, while one that runs on hydrogen fuel cells has a theoretical upper threshold of 85%.