An impedance model for the low-frequency noise originating from the dynamic hydrogen ion reactivity at the solid/liquid interface

- This work unveils the physics of the low frequency noise generation at the solid/liquid interface in ion sensors.
- A dedicated impedance model is established to correlate the noise generation to both thermodynamic and kinetic properties of the hydrogen ion site-binding reactions with the surface OH groups.
- It provides important guidelines for the sensing surface design aiming to minimize the LFN of ion sensors.

Understanding the dynamics of hydrogen ion reactivity at the solid/liquid interface is of paramount importance for applications involving ion sensing in electrolytes. However, the correlation of this interfacial process to noise generation is poorly characterized. Here, the relationship is unveiled by characterizing the interfacial process with impedance spectroscopy assisted by a dedicated electrochemical impedance model. The model incorporates both thermodynamic and kinetic properties of the amphoteric hydrogen ion site-binding reactions with the surface OH groups. It further takes into consideration the distributed nature of the characteristic energy of the binding sites. The simulated impedance matches the experimental data better with an energy distribution of the kinetic parameters than with that of the thermodynamic ones. Since the potentiometric low-frequency noise (LFN) originating from the solid/liquid interface correlates excellently with the real part of its electrochemical impedance spectrum, this work establishes a method for evaluating sensing surface quality aimed at mitigating LFN.