The question of how exactly protons move through water in an electric field has fascinated scientists for centuries. Now, more than 200 years after the last major insight into the phenomenon, scientists have some clarity.
In 1806, Theodor Grotthuss proposed a hypothesis, known as Grotthuss’s mechanism for “proton hopping,” as to how charge would flow through a water solution.
While Grotthuss’s hypothesis was very early thinking in his time – before protons, or even the very structure of water, were even known about – today researchers have long been known not to provide a perfect understanding of what happened in it. molecular
Recent discoveries in the subject may have revealed a mystery by unraveling the electronic structures of proton hydrates, which have remained elusive for so long.
The findings suggest that protons move through the water in “trains” of water molecules, with “tracks” built up ahead of the train and pulled out once they pass.
This loop can carry protons through water indefinitely. While the idea has been proposed before, the new study assigns another molecular structure that better fits the solution proposed by Grotthuss, according to the authors of the study.
“Debates about the Grotthuss mechanism and the nature of protons in water are heated, since this is one of the fundamental challenges of chemistry,” says chemist Ehud Pines from Ben-Gurion University of the Negev in Israel.
The new study is compelling because it combines a theoretical approach with physical experiments made possible by recent technological advances. The researchers used X-ray absorption spectroscopy (XAS) as an experiment to monitor how protons affected the electron charges on individual oxygen atoms in water.
As predicted, the greatest impact was on the three water molecules, although to different extents on each molecule within the trimeric cluster. Researchers have found groups of three molecules forming chains with protons.
The researchers also incorporated chemical simulations and calculations at the quantum level to determine the interactions between protons and neighboring water molecules as protons move through the liquid.
“Understanding this mechanism is pure science, pushing the boundaries of our knowledge and changing one of our fundamental understandings of one of the most important nature of mass and charge transport mechanisms,” says Pines.
The discovery plays into many other chemical processes, including photosynthesis, cellular respiration, and energy transport in hydrogen fuel cells.
Not only is the solution remarkable, but also how the researchers were able to approach it—testing and validating theoretical predictions against experimental results, and vice versa, in a long winding process that took nearly two decades from start to finish.
“Everyone has been thinking about this problem for over 200 years, so it was enough of a challenge for me to take it on,” says Pines. “Seventeen years later, I have found and demonstrated the most likely solution.”
The research was published in Angewandte Chemie International Edition.
#years #Key #Physical #Chemistry #Mystery #solved