Gadolinium-doped cerium oxide...The green doped deal

[Poolflood 845]

https://www.theregister.com/2020/11/03/greener_hydrogen_via_water_splitting/

 

Spoiler

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.

Hydrogen has been mooted as a green energy source for some time. It has nearly three times the energy density of petrol (gasoline) or diesel and when it is burned, the only byproduct is water.

The potential of the universe's most abundant element to help out in moving to a low-carbon economy is such that the EU has launched a strategy saying it was an "important part of the solution to meet the 2050 climate neutrality goal."

As well as hydrogen-cell cars, trains and aeroplanes powered by the gas are also being developed.

The problem is as things stand, around 96 per cent of industry hydrogen comes directly from fossil fuels. Not only does the process of extracting hydrogen release CO2, it often relies on carbon energy sources – creating a double impact on emissions. In some cases, CO2 released in the process can be captured and stored, offering so-called blue hydrogen.

But to get to hydrogen without releasing CO2 at all you need renewable electricity and electrolysis. Although this is the method preferred by low-carbon hydrogen investment, in the case of the EU strategy, it hits a problem when it comes to capital costs – the investment it takes to get up and running.

“You need a lot of two-dimensional cells that are stacked together and then you have to bring direct electricity via cable to each layer,” Professor Serra said.

The complex design ensures capital costs are high and the technology is difficult to scale, he added.

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.

"Electromagnetic processes such as microwave heating hold promise for smart manufacturing and activating chemical reactions and can enable electrochemical operation without contact electrodes and the restrictions of conventional electrolysis cells, those being constrained operation conditions and equipment complexity," the paper explained.

The technique could also be used to produce hydrocarbon fuels from carbon dioxide and water and make batteries that are faster to recharge than current technologies.

"This versatile technique opens the door to new, simpler, and energy-efficient routes for H2 production and the non-invasive electrification of catalytic reactions such as hydrocarbon synthesis and selective oxidations, along with gas separations and solid-state energy storage," the paper said.

The proposed method relies on cerium, but it could be developed with more common compounds of silicon, titanium, and iron, Professor Serra told The Register.

With the demonstration of the technology in the lab, he hoped to attract more interest from industry to help develop the technology, he said.

"We have demonstrated at bench scale, in the order of grams, and now we are talking to different partners and industries [about] scaling up and creating a demonstration pilot plant at kilogram scale capable of producing hydrogen for a family car, for example," he said.

Malte Jansen, an energy policy research associate at Imperial College London, said the development was a "really interesting prospect" but it may not have come soon enough to help contribute to meeting net-zero emission targets by 2050, part of the Paris Accord signed up to by major economies, excluding the US.

"It's really interesting to do hydrogen production in a way that doesn't require catalysts that are rare and expensive. However, if we are to meet 2050 targets, we are probably well advised to use technologies that are relatively mature and can be manufactured at a larger scale right now," Jansen said.

He said on average new energy technologies take around 18 years to mature and cost around €100m. "They are like very expensive children," Jansen told The Reg.