Dynamics of Hydrated Electrons in Aqueous Environments

Hydrated electrons, the transient species formed when free electrons become solvated by water molecules, occupy a central role in radiation chemistry, photochemistry and environmental processes. In bulk water, an excess electron induces a reorganisation of the hydrogen-bond network, forming a dynamic cavity in which it resides. This solvation structure evolves on ultrafast timescales as solvent molecules reorient and exchange, governing the electron’s localisation, mobility and reactivity. At interfaces, such as the water/air boundary, the electronic spectrum and diffusion pathways differ markedly from those in the bulk, with implications for interfacial redox chemistry and electron transfer. Experimental advances—most notably in time-resolved spectroscopy and liquid-microjet photoelectron techniques—coupled with high-level theoretical and machine-learning simulations, have begun to map the full sequence of events from electron injection, through initial localisation and vibrational relaxation, to eventual diffusion or recombination. These insights inform our understanding of radiolytic yields, pollutant degradation in natural waters and the design of photoelectrochemical systems.

Research from Nature Portfolio

Recent studies have resolved the behaviour of hydrated electrons at the water/air interface, employing time-resolved electronic sum-frequency generation spectroscopy to capture the interfacial electronic spectrum and follow the fate of electrons generated by photo-oxidation. These experiments reveal that, although the spectral maximum of the interfacial electron aligns with bulk values and remains localised predominantly within the water phase, its chemical pathway diverges: interfacial electrons diffuse into the bulk on sub-picosecond timescales, leaving reactive radicals at the surface. Parallel theoretical work has harnessed machine-learning-based potentials trained on correlated wave-function data to simulate the quantum dynamics of solvated electrons in bulk water. This approach reproduces the characteristic cavity structure, diffusion coefficients and vibrational signatures of the hydrated electron, offering a full quantum statistical treatment that bridges the gap between high-level electronic structure theory and long-time dynamical observables.

Dynamics of Hydrated Electrons in Aqueous Environments publication trend

The graph below shows the total number of articles in dynamics of hydrated electrons in aqueous environments across all publications each year (not limited to Nature Index journals).

Technical terms

Hydrated electron: An excess electron solvated by water molecules, forming a transient, self-stabilised cavity in the liquid.

Liquid-microjet photoelectron spectroscopy: An experimental technique that streams a micron-scale jet of liquid into vacuum to measure the kinetic energy of photoemitted electrons from aqueous samples.

Sum-frequency generation spectroscopy: A surface-sensitive optical method that probes electronic and vibrational states at interfaces by combining two laser beams of different frequencies.

Vertical binding energy: The energy required to detach a solvated electron from its solvent-stabilised state without allowing nuclear relaxation.

References

1. Spectroscopy and dynamics of the hydrated electron at the water/air interface. Nature Communications (2024).
2. Simulating the ghost: quantum dynamics of the solvated electron. Nature Communications (2021).
3. Genuine binding energy of the hydrated electron. Science Advances (2017).
4. Unravelling the Role of an Aqueous Environment on the Electronic Structure and Ionization of Phenol Using Photoelectron Spectroscopy. The Journal of Physical Chemistry Letters (2018).
5. Wavelength dependent mechanism of phenolate photooxidation in aqueous solution. Chemical Science (2023).