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A numerical framework for electrochemistry – application to the study of gas-evolving electro-chemical reactions

Thursday, 13 January, 2011 - 17:00
Campus: Brussels Humanities, Sciences & Engineering campus
Pedro De Mendonca Bernardo Maciel
phd defence

Production of gas is observed in many industrial electrochemical processes, in some cases as the goal of the process (e.g. in water electrolysis), while in others as the unwanted result of side reactions (e.g. in hydrogen gas bubble formation during zinc electrowinning). Due to the multi‐physical and multi‐scale nature of the phenomena involved, the gas phase is often overlooked; however, it exerts a strong influence at several levels, ranging from the hydrodynamics, to the mass and charge transfers in the reactor.

With the aim of improving the reliability of industrial reactor simulations, this work describes a numerical framework suitable for two‐phase electrochemistry. It includes the presentation of additional models ranging from supersaturation as the driving mechanism for gas bubble formation, to heterogeneous bubble nucleation, tracking bubble growth and detachment from the reactor surfaces, and to accounting for the bubbles movement in the electrolyte, both in momentum exchange with the flow and the consequential adjustment in electrolyte conductivity. Several couplings between the liquid and gas phases and electrochemistry models are realized.

The importance of combining the experimental side of electrochemistry with the numerical side is also outlined, in both the system definition (species diffusion coefficients, reaction rate constants and transfer coefficients) and in respect to the bubble size measurements which characterize the gas phase in to the system. This research has generated a profitable exchange of knowledge along its development among the two sides.