Electrochemistry and Quartz Crystal Microbalance with Dissipation monitoring (QCM-D) are two powerful techniques that, when combined, can offer new insights into material properties and electrochemical processes. Electrochemistry allows us to link an electrical potential difference to an identifiable chemical change, while QCM-D measures changes in mass and viscoelastic properties of thin layers at the sensor surface. By integrating these two methods, known as Electrochemical QCM-D (EQCM-D), it is possible to answer complex questions that neither technique could address alone. This synergy can provide helpful information in various fields, from electrometallurgy and battery technology to fuel cells and life sciences.
Let's look at how QCM-D data and electrochemical data can be combined, and the advantages of doing so. Electrochemistry enables the analysis of properties and behaviors of electrochemical systems, including redox reactions, electron transfer processes, electrochemical layer properties, and the characteristics of materials in various states of charge and discharge. QCM-D is a time-resolved gravimetric technique, which measures variations in mass and viscoelastic properties of thin films on the sensor surface. By merging these two types of methods, we can address questions that would not be possible to answer using either technique independently.
In this example, we use EQCM-D to analyze the reduction and oxidation of copper. We perform five voltammetry scans and simultaneously follow the mass and viscoelasticity via the QCM-D measurement. This allows us to measure the solid copper being deposited on the QCM-D sensor, and also to detect when it is being removed.
Figure 1. EQCM-D measurement of copper oxidation and reduction in five cycles. The voltammogram is shown to the left and the simultaneously collected QCM-D data to the right.
Fig. 1 shows the electrochemical cycling and the time-resolved QCM-D measurement of the mass uptake and mass loss of copper as it deposits and leaves the QCM-D sensor in each cycle. On the left, you see the five overlapping scans made in sequence, and on the right, the results from the QCM-D measurement during the electrochemical cycling.
When copper is reduced to solid copper on the sensor surface, which acts as a working electrode in the electrochemical cell, there is significant deposition and the QCM-D data shows a negative frequency shift of up to 500-600 Hz. The dissipation shift is relatively small, indicating rigid deposition at the surface. When the copper is oxidized again, the process reverses. The electrochemical data show no transient reactions that are non-reversible.
The simultaneous data from both techniques allows us to answer new questions that cannot be addressed by either technique alone. For example, from the electrochemical data, you cannot determine the amount of material being deposited on the sensor or the dynamics of the deposition, which can be seen in the QCM-D data. Conversely, the QCM-D data do not show the currents being generated. Thus, the complementary data enables us to answer new questions.
In the example above, QCM-D was combined with cyclic voltammetry. EQCM-D is, however, versatile, and other electrochemical methods, such as galvanostatic cycling, amperometric cycling, or impedance spectroscopy, could be used depending on whether you are interested in static current or potential, cycling potential, or the properties of the adlayers at the sensor surface.
Combining Quartz Crystal Microbalance with Dissipation and electrochemistry offers several benefits:
These benefits make the combination of QCM-D and electrochemistry a powerful tool for investigating surface phenomena and interfacial processes.
The integration of QCM-D and electrochemistry into EQCM-D offers a powerful and versatile tool for research across various fields. By providing detailed insights into both electrochemical processes and material properties, EQCM-D enables the exploration of complex questions that neither technique could address alone. This synergy, and the ability to simultaneously monitor electrochemical reactions and the corresponding changes in mass and viscoelastic properties at the sensor surface, makes EQCM-D a helpful tool for advancing technology and improving applications across diverse areas such as electrometallurgy, batteries, fuel cells, and life sciences.
To learn more about QSense EQCM-D, listen to the webinar below.
Erik is a Senior Application Scientist at Biolin Scientific. He has a broad scientific background from research projects and innovation management. Erik is particularly interested in surface science and has a Ph.D. in bioscience from 2013 where he developed biosensing applications focusing on QCM-D.
