Process intensification of green hydrogen production using 3D printed electrodes

Details

Supervisors

Proost, Joris

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil en chimie et science des matériaux, à finalité spécialisée

Abstract

Human activities are responsible for the global warming currently observed on Earth. The temperature increase is due to greenhouse gas emissions, which have been continuously increasing in recent decades. The use of renewable energy is an element of solution to limit greenhouse gas emissions but the use of renewable energy is intrinsically linked to intermittent electricity generation leading to excess or lack of energy. One of the solutions to reduce this intermittency is to transform the excess of renewable energy into hydrogen which can be stored by water electrolysis. Alkaline water electrolysis, which is the technology studied in this work, has the largest commercial outreach from all water electrolysis technologies. This master thesis is carried out in the context of exploring high applied current to improve the power and productivity of an electrochemical cell. High power cells are required to be able to use large excess of renewable energy. When operating at high current density, large amount of gas bubbles is produced in the electrodes. These bubbles limit the performance of the cell and therefore the efficiency of the reactions. Two different ways are explored to limit bubbles inside the electrodes are explored: forced electrolyte flux and the use of specific geometry for the electrodes thanks to the use of 3D printed electrode. For the forced electrolyte flux, the results show that when the electrolyte velocity is gradually increased, the cell voltage decreases sharply at the beginning and when the velocity is already high, the voltage is almost no longer affected by the velocity. The results also show that the decrease of voltage is observed for each structure except for one which is a limit case. But the magnitude of the decrease of voltage with an increased y-velocity depends on many factors such as the type of the structure, its size and the applied current. Concerning the geometry of the electrodes, the results show that Schwarz structure is more efficient than Gyroid to remove bubbles from the electrode. Another result is that the effect of the unit cell size is a function of the geometry used. Decreasing the unit cell size tends to increase the surface area but also to promote bubbles entrapment. From this it can be said that increasing the surface area of the structure is an efficient way to limit the cell voltage as long as bubbles are not trapped in the structure.