Stochastic Analysis of Electron Transfer and Mass Transport in Confined Solid/Liquid Interfaces

Molecular-level understanding of electrified solid/liquid interfaces has recently been enabled thanks to the development of novel in situ/operando spectroscopic tools. Among those, ambient pressure photoelectron spectroscopy performed in the tender/hard X-ray region and coupled with the “dip and pull” method makes it possible to simultaneously interrogate the chemical composition of the interface and built-in electrical potentials. On the other hand, only thin liquid films (on the order of tens of nanometers at most) can be investigated, since the photo-emitted electrons must travel through the electrolyte layer to reach the photoelectron analyzer. Due to the challenging control and stability of nm-thick liquid films, a detailed experimental electrochemical investigation of such thin electrolyte layers is still lacking. This work therefore aims at characterizing the electrochemical behavior of solid/liquid interfaces when confined in nanometer-sized regions using a stochastic simulation approach. The investigation was performed by modeling (i) the electron transfer between a solid surface and a one-electron redox couple and (ii) its diffusion in solution. Our findings show that the well-known thin-layer voltammetry theory elaborated by Hubbard can be successfully applied to describe the voltammetric behavior of such nanometer-sized interfaces. We also provide an estimation of the current densities developed in these confined interfaces, resulting in values on the order of few hundreds of nA·cm−2. We believe that our results can contribute to the comprehension of the physical/chemical properties of nano-interfaces, thereby aiding to a better understanding of the capabilities and limitations of the “dip and pull” method.