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Climate Energy

Getting over a stumbling block on the road to renewable energy storage

Engineers must discover a means to store renewable energy reliably and on a massive scale if renewable energies are to someday substitute fossil fuels. Several researchers are now investigating the prospects of storing energy in a gaseous state inside electrolytic cells.

Electrolytic cells work by causing water molecules to split into hydrogen and oxygen through an electrolysis reaction triggered by electricity. After then, the electricity can be retrieved by reversing the process and recombining the oxygen and hydrogen to form new water molecules.

 

Knowing how catalysts function is essential.

Catalysts are utilized to speed up electrocatalytic reactions without ever being consumed. Metal oxides are utilized as catalysts in the water electrolysis process, with some of them performing better than others for unknown reasons. “We’ve seen that some oxides are very effective, robust, and stable during water electrolysis,” explains Vasiliki Tileli, who is an assistant professor and leader of EPFL’s Laboratory for in situ Nanomaterials Characterization with Electrons. “However, because we don’t know precisely what occurs to the catalyst throughout the reaction, we can’t truly explain why some oxides work better.”

A catalyst of the next generation

Tileli with Tzu-Hsien Shen, who is a Ph.D. student in her lab, examined water electrolysis processes under an electron microscope, obtaining nanoscopic-scale images to examine how the catalyst reacts throughout the process. They employed BSCF, a perovskite-form oxide catalyst. Tileli describes it as “an unusual catalyst with outstanding water-splitting characteristics.” “The majority of currently used catalysts, such as those made of iridium and ruthenium, are efficient but costly, and their supply is restricted. Alternatives will have to be found at some point.”

Tileli and Shen photographed BSCF particles in real-time during each phase of the electrolysis cycle. They noticed molecular oxygen, which indicated that the reaction was occurring, and verified that the reaction was reversible. They also discovered that BSCF is extremely durable.

Switching from hydrophobic to hydrophilic surfaces

Furthermore, the researchers discovered that throughout the reaction, the surface atoms of the particles rearrange, affecting the surface properties. As a result, during different stages of the electrolysis cycle, the particles are able to interact with their surroundings differently. During some processes, the surface is hydrophobic (water-repellent), whereas during others, it is hydrophilic (i.e., attracted water). “These are one-of-a-kind observations,” Tileli explains. “We guessed that the particle surface was changing, but even this had never been witnessed in real-time at the nanoscopic scale.” Engineers value a material’s capacity to flip between hydrophobic and hydrophilic states, which can be employed in a range of applications including water purification systems, sensors, and self-cleaning surfaces. Nature Catalysis published the researchers’ findings.

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