Global Energy Development News Feed
The Race for Solar Julien Happich June 19th 2017
'Solar' Paint Harvests Energy from The Air
Researchers from RMIT University (Melbourne, Australia) and MIT (Cambridge, MA) have developed a sunlight-absorbing paint able to harvest hydrogen from air moisture, by splitting water molecules.
The catalyst for this solar-powered hydrolysis comes in the shape of molybdenum sulfides that could readily be mixed to the titanium oxide particles typically used in white paint.
In a recent paper titled "Surface Water Dependent Properties of Sulfur-Rich Molybdenum Sulfides: Electrolyteless Gas Phase Water Splitting" published in the ACS Nano journal, the researchers report that sulfur-rich MoSx (x = 32/3) is a highly hygroscopic semiconductor which can reversibly bind up to 0.9 H2O molecule per Mo.
On that basis, they developed an electrolyteless water splitting photocatalyst (formulated as an ink) that relies entirely on the hygroscopic nature of MoSx as the water source, and which could be coated onto insulating substrates, such as glass, to obtain hydrogen and oxygen from water vapor.
Distinguished Professor Kourosh Kalantar-zadehand Dr Torben Daeneke with a pot of solar paintand a piece of glass with the paint applied.
Sharing their story on the RMIT University's news feed, the researchers were keen to put the emphasis on the potential for cheap paint-based hydrogen fuel production, though collecting the useful gas would not be as simple as spraying the paint on a brick wall, as most media reported.
So this got me thinking. To design a practical hydrogen harvesting solution based on this type of paint, you'd need a way to concentrate the generated hydrogen and store it away (from oxygen among other things to prevent counterproductive recombination).
Necessarily, that would mean using some sort of encapsulation, maybe enclosing the water splitting paint within a double-glazed panel. But then, encapsulation means no gas renewal, which defeats the whole concept.
As for hydrogen collection, I imagine some specifically designed H2 adsorbing materials could store it and make it available for a purpose-made integrated fuel cell. I sent out my questions to lead author Dr Torben Daeneke to understand where the research was heading for a practical implementation.
"You are correct to say that the produced oxygen and hydrogen will need to be removed from the surface. In our lab experiment we placed the catalyst inside a glass vessel that was sealed," Daeneke replied.
The Race for Batteries Nick Flaherty June 12th 2017
New Liquid Metal Battery May Solve Renewable Energy Storage Problem
The team at the Department of Materials Science and Engineering at the Norwegian University of Science and Technology ( NTNU) in Trondheim have developed a battery system with three liquid layers: sodium at the top as the negative electrode, a sodium chloride based electrolyte in the middle, and zinc at the bottom as the positive electrode.
To prevent the zinc containing ions from reacting with the sodium electrode, a porous diaphragm or separator is placed between the electrodes. Avoiding a brittle, expensive β-alumina ion selective membrane and replacing it with a cheap durable diaphragm material significantly improves the performance and reduces the cost of liquid metal batteries.
The choice of immiscible electrolytes and electrodes will ensure a safe battery system, which in the unlikely event of mechanical failure will discharge without any undesired effects such as fire or explosion. This compares to sodium sulphur (NaS) molten salt batteries which have been demonstrated for grid storage.
They require a sodium ion selective membrane which adds a great deal of expense and resistance to the cell and in the event of rupture or cracking of the membrane a vigorous reaction occurs, possibly resulting in fires.
The team at NTNU are working with local molten salt electrochemistry expert SINTEF on lab scale cell design and development as well as the testing of the battery performance and materials.
The project is funded by The Research Council of Norway and runs until 2018.