Master assignment - Influence of the gas properties and bubble formation on the electrochemical performance of a hollow fiber electrode

Master project proposal "Influence of the gas properties and bubble formation on the electrochemical performance of a hollow fiber electrode"

Motivation

A hollow fiber electrode (HFE) is a tubular, porous, metal electrode [1]. In Figure 1, a SEM picture of a titanium HFE can be seen.

^{Figure 1: SEM images of titanium hollow fiber electrode.}

Since it is a porous material, a gas can be purged through the pores of the electrode. Bubbles emerge from the electrode surface and ascend. These bubbles induce mixing of the electrolyte, resulting in better mass transport. The improved mass transport results in a better electrochemical performance. Experimentally this becomes evident when the current is measured as a function of gas flow speed through the fiber [2]. For example, in Figure 2 this relation can be seen for the oxidation of Fe^II to Fe^III.

^{Figure 2: The current at 1.2 V vs RHE as a function of the argon gas flow speed for the oxidation of Fe(II) to Fe(III). From [2].}

The HFE has been applied in reaction systems with various gasses such as argon [2], carbon dioxide [3], nitric oxide [4] and propylene [5]. The influence of the flow speed of these gasses on their specific reaction system have been studied. However, all these gasses have different properties. From previous tests in the lab, we know e.g. that fewer and smaller bubbles emerge from the electrode when helium, is used. This is illustrated by Figure 3 below.

^{Figure 3: 20 ml/min of helium, nitrogen and argon through a titanium hollow fiber.}

Based on these observations, the question arose if and how gas properties influence the electrochemical performance of the hollow fiber electrodes.

 Assignment

In this work, the relationship between gas properties, bubble formation and electrochemical performance in hollow fiber electrodes will be studied. The responses of the current to gasses with different properties will be compared to one another. The emerging of the bubbles at the electrode surface will be studied by using high-speed imaging combined with electrochemical systems. The quantification of the bubble distribution will be done based on the imaging and serve as input to the modelling of  the mass transfer and mixing in the liquid. The results of these experiments will contribute to a firm understanding of the operating principle of the hollow fiber electrode.

The following electrochemical system will be used in this assignment. As working electrode, a platinized titanium hollow fiber will be used. The reaction of interest is, initially, the oxidation of ferrocene. If the study progresses well, it can be expanded by studying the influence on the hydrogen evolution reaction as well.

This assignment is a collaboration between POF (Physics of Fluids group) and PCS (Photocatalytic Synthesis group). The high-speed imaging studies will be conducted in the POF labs. The majority of the electrochemical experiments will be performed in the PCS labs.

Contact & Supervision

For any further questions, feel free to contact Tessa de Koning Gans (t.dekoninggans@utwente.nl)

 References

[1] Jong, Ronald & Krzywda, Piotr & Benes, Nieck & Mul, Guido. (2020). Preparation of Ti, Ti/TiC or Ti/TiN based hollow fibres with extremely low electrical resistivity. RSC Advances. 10. 31901-31908. 10.1039/D0RA04905K.

[2] Jong, Ronald & Mul, Guido. (2022). Gas flow Stimulated Hydrodynamics for Preparation and Application of Platinized Titanium Hollow Fibre Electrodes. ChemElectroChem. 9. 10.1002/celc.202101135.

[3] Kas, R., Hummadi, K., Kortlever, R. et al. Three-dimensional porous hollow fibre copper electrodes for efficient and high-rate electrochemical carbon dioxide reduction. Nat Commun 7, 10748 (2016). https://doi.org/10.1038/ncomms10748

[4] Krzywda, Piotr & Paradelo Rodríguez, Ainoa & Benes, Nieck & Mei, Bastian & Mul, Guido. (2022). Effect of Electrolyte and Electrode Configuration on Cu‐Catalyzed Nitric Oxide Reduction to Ammonia. ChemElectroChem. 9. 10.1002/celc.202101273.

[5] Jong, R.P.H. & Dubbelman, Emilie & Mul, G.. (2022). Electro-oxidation of Propylene by Palladium functionalized Titanium Hollow Fibre Electrodes. Journal of Catalysis. 416. 10.1016/j.jcat.2022.10.007.