ABSTRACT
Electrochemical systems using a gas evolving electrode, such as metal-air batteries or electrolyzers, are confronted with recurrent problems related to gas production. Indeed, the production of gas at the surface of the electrodes causes a masking of the active surface which induces overvoltages and unstable electrical signals in time. We propose here numerical computations that take into account the spatial heterogeneity of the electrode and allow to account for the size distribution of the produced bubbles. We compare these computations to experiments on a Platinum-Carbon plate cell in the presence or absence of electrolyte flow. They reproduce the observed behavior and allow us to predict the stability of the signals. They are also a guide for the synthesis of efficient electrodes.
ABSTRACT
In this study, the effect of flow of the electrolyte on an electrolysis cell and a zinc cell is investigated. The gain of energy brought by the flow is discussed and compared to the viscous losses in the cells. We point out that the balance between the gained electrical power and the viscous loss power is positive only if the hydrodynamic resistance of the circuit is correctly designed and further comment on the economical viability of the whole process. A model of the studied phenomena is proposed in the last section. This analytical model captures the dynamics of the process, gives the optimal flowing conditions and the limits of the energetical rentability of the process. This study shows that the use of flowing electrolyte in zinc-air batteries can be energetically profitable with the appropriate flowing conditions.
ABSTRACT
Aqueous biphasic systems (ABSs), in which two aqueous phases with different compositions coexist as separate liquids, were first reported more than a century ago with polymer solutions. Recent observations of ABS forming from concentrated mixtures of inorganic salts and ionic liquids raise the fundamental question of how "different" the components of such mixtures should be for a liquid-liquid phase separation to occur. Here we show that even two monovalent salts sharing a common cation (lithium) but with different anions, namely, LiCl and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), may result in the formation of ABSs over a wide range of compositions at room temperature. Using a combination of experimental techniques and molecular simulations, we analyze the coexistence diagram and the mechanism driving the phase separation, arising from the different anion sizes. The understanding and control of ABS may provide new avenues for aqueous-based battery systems.