After 200 years, a fundamental puzzle in physical chemistry may have been solved: ScienceAlert

The question of how accurately protons move through water in an electric field has fascinated scientists for centuries. Now, more than 200 years after the last insight into the phenomenon, scientists have some clarity.

In 1806, Theodor Grottos put forward a hypothesis known as Grottos mechanism For “proton jump”, on how charge flows through a solution of water.

Whereas the Grottos hypothesis was very progressive thinking for its time – coming before protonsor even the actual structure of water, was even known – modern researchers have long known that it did not provide a complete understanding of what happened at the molecular level.

The latest findings on this topic may have unlocked the mystery by solving the electronic structures of wet protons that have been elusive for so long.

The results suggest that the protons move through the water in “trains” of three water molecules, with “tracks” built in front of the train as it advances and pulling upwards once it has passed.

This loop can continue indefinitely to move protons through the water. While the idea has been proposed before, the new study identifies a different molecular structure that best fits Grotthuss’ proposed solution, according to the study’s authors.

“Discussions about the Grottos mechanism and the nature of the proton’s solubility in water have intensified, as this is one of the most fundamental challenges in chemistry,” Chemist Ehud Pines says: from Ben-Gurion University of the Negev in Israel.

The new study is compelling because it combines a theoretical approach with physical experimentation Made possible by recent technological advances. Researchers used X-ray absorption spectroscopy (XAS) to observe how proton charges affect electrons in single oxygen atoms in water.

As expected, the effect was greater on three water molecules, albeit to varying degrees on each individual molecule inside the triple block. The researchers found groups of three molecules that form chains with the proton.

The researchers also combined quantum-level chemical simulations and calculations to determine the interactions between protons and neighboring water molecules as the protons moved through the liquid.

“Understanding this mechanism is pure science, pushing the boundaries of our knowledge and changing one of our basic concepts for one of the most important mechanisms of mass transport and shipping in nature,” Baines says.

This discovery plays a big role Other chemical processesincluding photosynthesis, cell respiration, and energy transfer in hydrogen fuel cells.

Not just the remarkable solution but also how the researchers got there—testing and validating theoretical predictions against experimental results, and vice versa, in a long and winding process that took nearly two decades from start to finish.

“Everyone has thought about this problem for over 200 years, so it was challenging enough for me to decide to take it up,” Baines says. “Seventeen years later, I’m grateful that I probably found and demonstrated the solution.”

The search was published in Angewandte Chemie International Edition.