probing interfacial electrochemistry

Combined method for probing interfacial electrochemistry in better detail

Electrochemists from RIKEN have studied the distribution of electrical charges at the user interface between the electrode and electrolyte utilizing a 2-pronged method to comprehend and develop more-effective energy storage systems.

Devising potent batteries and fuel cells need an understanding of how ions and electrons act at the interface between the electrode and an electrolyte – the liquid in which the electrode is submerged. When voltage is applied, the electrode gets charged, and ions with the opposing charge start to build upon its surface. With ion concentration lowering with distance from the electrode, it builds a layer on the electrode. However, the correlation between the electrode-electrolyte interface’s electrochemical properties and the ion structure is unknown.

probing interfacial electrochemistry
Figure: Schematic of an electrochemically active ferrocene-terminated self-assembled monolayer on gold, which was used as a model electrochemical interface. The electrochemical environment is illustrated by the potential profile across the interface (dashed line) and it was spectroscopically probed in the experiment. Image Credits: CC BY 4.0 © 2020 R. A. Wong et al.

The structure and energetics of the charged interface between the gold electrodes and different electrolytes were examined by Raymond Wong from RIKEN Surface

and Interface Science Lab and his co-workers.

A monolayer of redox-active molecules was assembled on the electrode surface, where one edge of the molecules – a ferrocene head consisting of an iron atom – was opened to the electrolyte, and the other edge was attached to the electrode. Using an ideal voltage that triggers the ferrocene system to switch over between neutral and positively charged states, and it can be quickly oxidized and reduced.

Wong and his colleagues mixed cyclic voltammetry, which is usually utilized in electrochemistry, with photoelectron spectroscopy. It gives direct details on the function of the electrons at the electrode-monolayer-electrolyte interface. The team carried out the electrochemical estimations in a chamber, which was later removed and shifted to an ultrahigh-vacuum chamber to perform spectroscopic determinations. This procedure allowed the researchers to get snapshots of the electrode-monolayer-electrolyte interface under various applied potentials.

He further added that their objective was to get an enhanced insight at the microscopic and molecular levels of the electrode-electrolyte interface. Such insights are not conveniently obtainable by other electrochemical or in situ approaches.

The method is adaptable, can be used in other systems, and elongated to examine the interfacial energetics in semiconducting electrodes. This can also contribute more understandings into electrolyte impacts and interfacial energetics in other surface-bound redox-active systems with significance in redox-induced nano actuators, pseudocapacitive energy storage, and biochemical sensing.

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Combined method for probing interfacial electrochemistry in better detail

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