They are observing for the first time how water is formed at the molecular level.
Scientists from Northwestern University in the USA for the first time witnessed in real time and at the molecular level the fusion of hydrogen and oxygen atoms to form tiny nanometer-sized water bubbles. The development comes as part of a new study in which researchers sought to understand how palladium, a rare metal element, catalyzes the gas reaction to form water. By observing the reaction at the nanoscale, the team unraveled how the process occurs and even discovered new strategies to speed it up.
Because the reaction does not require extreme conditions, scientists say it can be used. as a practical solution for quickly obtaining water in arid conditions, even on other planets, which could prove very useful in future space missions. The study was published in the Proceedings of the National Academy of Sciences (PNAS).
“By directly visualizing water generation at the nanoscale, we were able to determine the optimal conditions for rapid water generation under ambient conditions,” he says in a statement. Vinayak Dravidprofessor of materials science and lead author of the study, who adds that “these results have important implications for practical applications, such as enabling rapid production of water in deep space using gases and metal catalysts without requiring extreme reaction conditions.”
“Think of Matt Damon’s character, Mark Watney, in The Martian. He burned rocket fuel to produce hydrogen and then added oxygen from his oxygenator. Our process is similar, except we avoid the need for fire and other extreme conditions. We are simply mixing palladium and gases,” Dravid compares.
Palladium as a catalyst
Since the early 20th century, researchers have known that palladium can act as a catalyst to quickly form water, but exactly how this reaction occurs remains a mystery. “This is a known phenomenon, but it has never been fully understood,” he says. Yukun Liuthe study’s first author and a PhD candidate in Dravid’s lab, who points out that “it is necessary to combine direct visualization of water formation and atomic-scale structure analysis to figure out what’s going on with the reaction and how to optimize it.” This.” “.
However, it was impossible to see this process with atomic precision just nine months ago. In January 2024, Dravid’s team introduced new method for analyzing gas molecules in real timeby developing an ultrathin glassy membrane containing gas molecules inside honeycomb nanoreactors so they can be viewed in high-vacuum transmission electron microscopes.
Using the new technique, previously published in the journal Science Advances, researchers can examine gas samples at atmospheric pressure with a resolution of just 0.102 nanometers, compared to 0.236 nanometers using other modern instruments. This method also allowed for the first time the simultaneous analysis of spectral and mutual information. “By using an ultra-thin membrane, we get more information from the sample itself. Otherwise, information from a thick container will interfere with analysis,” he says. Kunmo Kufirst author of the article “Progress of Science”.
Using new technology, Dravid, Liu and Koo investigated the reaction of palladium. First, they observed how hydrogen atoms penetrated palladium, expanding its square lattice. But when they saw tiny bubbles of water forming on the surface of the palladium, the researchers couldn’t believe their eyes. “We think this may be the smallest bubble ever formed that has been directly observed. This is not what we expected. Luckily, we recorded it so we could show other people that we weren’t crazy,” Liu recalls. “We were skeptical,” adds Koo, who explains that they needed to “do more research to prove that water was actually formed.”
Bubble analysis
The team implemented a technique called electron energy loss spectroscopyfor bubble analysis. By studying the energy loss of scattered electrons, the researchers determined the oxygen-binding characteristics unique to water, confirming that the bubbles were indeed water. They then confirmed this result by heating the bubble to estimate the boiling point. “This is a nanometer-scale analogue of the Chandrayaan-1 lunar rover experiment, which looked for evidence of water in the lunar soil,” says Ku. “During his exploration of the Moon, he used spectroscopy to analyze and identify molecules in the atmosphere and on the surface. We used a similar spectroscopic approach to determine whether the product formed was indeed water.”
Having confirmed that the palladium reaction produces water, the researchers tried to optimize the process. They added hydrogen and oxygen separately at different times or mixed them together. to determine which sequence of events generates water at the fastest rate.
Dravid, Liu and Ku found that adding hydrogen first and then oxygen resulted in the fastest reaction rate. Because hydrogen atoms are so small, they can squeeze between palladium atoms, causing the metal to expand. After filling the palladium with hydrogen, the researchers added oxygen gas.