Probing Interfacial Water Dissociation at the Nanoscale with a Quantum Sensor.

Area of Science:

• Surface science
• Physical chemistry
• Quantum sensing

Background:

• Controlling interfacial chemical reactions is vital for electrochemistry and photochemistry.
• Advanced techniques are needed to monitor reactions at the nanoscale.

Purpose of the Study:

• To develop and apply a new interface-sensitive magnetic resonance technique.
• To investigate water dissociation at a hydrophilic diamond surface.
• To monitor elementary steps like electron transfer and diffusion.

Main Methods:

• Combined qPlus-based scanning probe microscopy (SPM) with quantum sensing using a single nitrogen-vacancy (NV) center.
• Utilized SPM tip for local electron injection into interfacial water.
• Employed NV center for sensitive detection of interfacial processes.

Main Results:

• Observed specific configurations of hydrated electrons (e(aq)^-) at the interface with a hyperfine interaction of ~28 MHz.
• Demonstrated that hydrated electrons induce water dissociation.
• Found that hydroxides diffuse ~2.3 times faster than water molecules at the interface.
• Diffusion coefficients at the interface are significantly lower than in bulk, but their ratio is preserved.

Conclusions:

• The combined SPM and quantum sensing technique offers a new platform for studying interfacial chemical reactions.
• Detailed electronic and nuclear processes at interfaces can be revealed with nanometer resolution.
• Provides fundamental insights into water-surface interactions and reaction dynamics.