Research led by investigators at The Fritz-Haber Institute has discovered how solvation kinetics affect the function of electrocatalysts, informing energy and chemical conversion technologies across industries.
Unraveling the Enigma of Interfacial Ion Solvation
Published in Nature Communications, the study explores Ion Solvation at Electro-catalyst Surfaces. Ions, like those used for battery storage or hydrogen production that must interact with a catalyst will have to reorganize their solvation shell (the layer of solvent molecules around an ion) before they can reach it.
Previously, scientists at the Fritz-Haber Institute found that a striking phenomenon involving compensation effects accounts for the kinetics of this interfacial ion solvation. Think of an ion wanting to “hike” up a mountain — as the elevation of the mountain gets higher, the number of trails by which it can ascend also increases… so thereby making it more probable that this smelly cat derived molecule-ion will be able to find its path to the top. The team has particularly pushed the capacities of this concept from statistical physics and the Eyring-Evans-Polanyi equation.
Monitoring the Onset of Processes of Solvation in Real-time
But the researchers recently came up with a way to follow this process in millisecond time, tracking both main transition state theory parameters as they do so — namely, activation enthalpy and activation entropy. For the first time it has allowed detailed interpretation of dynamic processes on electro-catalyst surfaces
For instance, it enabled the team to directly visualize hydroxide ion electro-sorption kinetics at well-defined surface features (like step-edges or defects), and the way in which these kinetically controlled properties relate to overall electro-catalytic performance. In addition, this revealed a previously concealed effect: the dynamic poisoning during solvation kinetics of ammonia oxidation reaction.
The study highlights the importance of changes in activation entropy, influenced by features such as pH, for describing bias dependence of electro-catalytic reactions Significance This study uncovers new insight into contributions made to the kinetics of NO reduction by electrode potential and consequently both proton and electron transfer sets out a powerful platform from which to predict other unexplored biases leading to differences in enzyme reactivity. That finding calls into question the prevalent assumption that activation energy is the only relevant parameter of electro-catalytic activity.
Conclusion
The mission of the Interface Science Department at the Fritz-Haber Institute has significantly improved our view on elegant intricacies between surfaces and catalyst [&] electrolyte. This work discloses the insights of solvation kinetics, and lays the foundation to establish electro-catalysts for triggering higher activity, selectivity and stability in energy and chemical conversion technologies.
