Guest essay by Eric Worrall
Researchers in Spain claim their breakthrough cuts the cost of electrolysis cells, by replacing the traditional arrangement of layered electrode plates with a much simpler electrochemical system.
H2? Oh! New water-splitting technique pushes progress of green hydrogen
It’s really dope. Yep it’s an energy-efficient process kicked off by gadolinium-doped cerium dioxide
Lindsay Clark Tue 3 Nov 2020
Researchers in Spain have uncovered a new approach to producing hydrogen via water splitting which could help overcome some of the drawbacks to this promising alternative fuel source.
In a study published in Nature Energy, Valencia University researcher José Manuel Serra, professor José M Catalá-Civera, and their colleagues describe a method for producing hydrogen gas by blasting microwave radiation at a watery chemical soup. The approach could make extracting hydrogen from water cheaper, and more importantly, reduce the capital costs of the necessary machinery.
The cyclical process proposed by the research team uses a soup of gadolinium-doped cerium oxide and water. Applying microwaves to the mixture electrochemically deoxygenates the cerium oxide, but when the microwaves stop, there’s a reaction with the water, and the cerium re-oxygenates and produces free hydrogen.
Read more: https://www.theregister.com/2020/11/03/greener_hydrogen_via_water_splitting/
The abstract of the study;
Hydrogen production via microwave-induced water splitting at low temperature
J. M. Serra, J. F. Borrás-Morell, B. García-Baños, M. Balaguer, P. Plaza-González, J. Santos-Blasco, D. Catalán-Martínez, L. Navarrete & J. M. Catalá-Civera
Supplying global energy demand with CO2-free technologies is becoming feasible thanks to the rising affordability of renewable resources. Hydrogen is a promising vector in the decarbonization of energy systems, but more efficient and scalable synthesis is required to enable its widespread deployment. Here we report contactless H2 production via water electrolysis mediated by the microwave-triggered redox activation of solid-state ionic materials at low temperatures (<250 °C). Water was reduced via reaction with non-equilibrium gadolinium-doped CeO2 that was previously in situ electrochemically deoxygenated by the sole application of microwaves. The microwave-driven reduction was identified by an instantaneous electrical conductivity rise and O2 release. This process was cyclable, whereas H2 yield and energy efficiency were material- and power-dependent. Deoxygenation of low-energy molecules (H2O or CO2) led to the formation of energy carriers and enabled CH4 production when integrated with a Sabatier reactor. This method could be extended to other reactions such as intensified hydrocarbons synthesis or oxidation.
Read more: https://www.nature.com/articles/s41560-020-00720-6
Cerium is a rare earth mineral, mostly extracted in China. The current world price for Cerium Oxide is around $1800 / ton, though this could rise if everyone suddenly needs Cerium for their green revolution hydrogen electrodes. Having said that, Cerium is the 26th most abundant element in the Earth’s crust, more abundant than lead, so in principle there is plenty of Cerium available to extract if demand rises.
It will be interesting to see how well this process scales out of the lab. The most common problem with catalytic processes like this is impurities in the water poisoning the catalyst. As water is electrolysed, it would tend to leave behind and concentrate any unwanted contaminants in the Cerium Oxide.
For example if some of the Cerium catalyst came in contact with sulphur instead of oxygen during the hydrogen production phase, because the water being electrolysed was contaminated with a small amount of sulphur, the resulting Cerium sulphide ceramic might be durable enough to survive the microwave regeneration phase.
Despite the potential cost saving of this new catalyst, the green hydrogen produced by this generator is still very expensive, because of the cost of the renewable energy which is required to fuel the process.