Study shows potential for more affordable and efficient hydrogen gas production
A recent advance in the science of hydrogen fuel production could enable higher output and more sustainable production of this renewable energy source, researchers with Stockholm’s KTH Royal Institute of Technology report.
The findings result from unprecedented atomic-scale observations of how catalysts perform in the slow and expensive process of water splitting, or breaking the bond of oxygen and hydrogen. Using a unique set-up, they were able to produce hydrogen gas at rates comparable to or faster than state-of-the-art conventional catalysts.
What’s more, the catalyst remained in good condition after extended operation – a positive sign for commercial viability.
The research was reported in Nature Chemistry, led by KTH Professor Lichen Sun with contributions from KTH Professor Mårten Ahlquist and doctoral researcher Hao Yang.
Water splitting with electrolysis depends on electricity to break the bond of H20 into hydrogen and oxygen gases. Nickel–iron oxides are widely used as catalyst to lower the amount of electricity required and speed up the formation of H2 and O2 gases. While effective, these materials are also complicated, making it difficult for scientists to see exactly how the chemical reactions happen.
The solution
The team cracked the challenge by engineering a molecular scaffold—a specially designed organic structure that holds nickel and iron atoms in fixed positions. In contrast to the random scattering of nickel and iron in a conventional catalyst, this precise arrangement allowed the researchers to study the transfer of electrons and protons at the heart of the process.
And in doing so, they discovered how positioning iron and nickel atoms closer together helps hydrogen ions move away from the iron parts of the catalyst to enable oxygen to form – the hardest part of splitting water. Sun says the observations revealed hydroxyl groups (chemical units of oxygen and hydrogen) attached to nickel act as proton relays, which expedites their movement.
The researchers also found an optimal balance of pH to speed up the formation of the O-O bond while maintaining its synchronization with electron transfer.
“The molecular scaffold enabled us to finally see the proton relay in action,” Sun says. “This insight explains why nickel and iron work so well together—and how we can make them even better.”
The researchers caution that direct comparisons with conventional state-of-the-art catalysts are difficult to make, given the variety of systems and experimental conditions. Nevertheless, they say the catalytic activity they achieved approximated an order-of-magnitude enhancement operating at similar voltage.
”That’s important because higher turnover rates reduce energy losses and operating time, which then lowers the cost per kilogram of hydrogen,” Ahlquist says.
“Our findings connect the dots between real-world nickel–iron oxide catalysts and a detailed molecular understanding,” Ahlquist says. “This opens a path to create next-generation materials that work even better and last longer. For hydrogen technology, that means faster, more efficient and more sustainable ways to produce clean fuel.”
David Callahan