Praveen Kumar Selvam is one of our researchers at the University of Galway, in Ireland. Galway acts as project coordinator, as well as designs catalysts to accelerate water splitting, replacing rare and scarce metals like platinum and ruthenium with more abundant and sustainable raw materials.
“I was aware of environmental issues, so I wished to contribute my part to mitigating carbon dioxide emissions,” says Kumar Selvam. He took an interest in hydrogen production early in his career, already during his Bachelor’s in Nanoscience and Technology. Now, he is a PhD researcher at the ChemLight group, led by Pau Farràs, focusing on the synthesis of catalysts, and incorporating them into inks and powders, formulations that facilitate further manufacturing.
Back then, Kumar Selvam did some research and concluded that hydrogen could become a billion-dollar market. Curious about the technology that would be game changers within this field, he found out that very few people were working in seawater electrolysis. While others saw challenges and complications, Kumar Selvam became immediately hooked – seawater electrolysis has been his primary interest ever since.
Kumar Selvam started his PhD in the University of Galway in February last year, mostly to join the ANEMEL consortium. “We are leading the development of electrocatalysts within the project, particularly the development of oxidation reaction catalysts,” he says.
Electrolysers consist of two separate electrodes: the anode and the cathode . The anode witnesses the oxygen evolution reaction (OER) and the cathode conducts the hydrogen evolution reaction (HER). Each side reaction requires different catalysts, due to distinct chemical requirements. Kumar Selvam’s work focuses on the anode, studying different nickel and iron salts, especially oxides, sulphides, and selenides, because in ANEMEL we have observed that they improve factors such as conductivity and stability of the electrode. Additionally, nickel and iron are cheap and abundant metals.
The aim is to develop what’s known as a “high entropy material“, which consists of a combination of five or more elements and presents interesting properties for a promising catalyst. Why that? Thanks to a stable structure and a tremendous tuneability, high entropy materials address the two main challenges of seawater electrolysis: increasing the current density and reducing corrosion.
Kumar Selvam and the Galway team test catalysts with a trial-and-error strategy – quite common in research. It sounds a bit unsophisticated, but it works. “Let’s say we put two elements in one material, then three, four, and so on. By comparing them, we can see which element contributes to the current density variable and which element contributes to the corrosion resistance. We can then change the percentage of the different elements depending on these two properties, optimise them, and obtain a high current density and corrosion-resistant catalyst in a single material,” he explains. So far, he has synthesised around ten high entropy materials that serve as anodic catalysts, and the ANEMEL team is testing them for the electrolysis of low-grade saline water, a gentler environment that seawater.
In the field of catalysts, size matters. The smaller, the better, Kumar Selvam explains. “Let’s say you have a sugar cube and sugar powder. Which one will mix faster in water? The powder,” he says. The higher contact surface speeds up the solvation, same thing for catalysis. “When the size [of the catalyst] is reduced, the reaction rate [raises, and] everything will speed up. That’s why we move to the nano range. This will increase the conductivity and the catalytic properties, and it will also act as corrosion resistance.”
Together with mixing all these materials to create a highly functional catalyst, the ANEMEL team face other challenges. One of these is choosing the material that will act as a substrate for their catalysts — catalysts are sprayed onto it like a painting, so the substrate acts as a canvas.
Typically, in anion exchange membrane electrolysers, nickel foam is the best substrate. However, in a saline environment, nickel is not a very good choice, as it corrodes in about 10 minutes. Therefore, researchers must find alternative substrates with improved stability and durability.
‘So far, we have found that titanium is a very good substrate in the saline environment. It is stable and resists corrosion in the long term,” says Kumar Selvam. The problem with titanium is low conductivity. ANEMEL researchers work towards solving that, as well as designing a protective layer for the nickel foam. Plus, the team must manage without critical raw materials (CRMs), such as cobalt or platinum. Not an easy task.
Luckily, every effort has its reward – eventually. Avoiding CRMs will decrease the price of catalysts, as well as the overall cost of the electrolyser setup, making our solution more attractive and competitive for the market. Moreover, not using scarce and critical raw materials will avoid potential supply risks and conflicts, making our green hydrogen even greener.
