Magnetic field-driven enhancement of hydrogen production in water electrolysis

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Recent developments in energy production aim to increase the application of renewable resources. In this perspective, hydrogen production by water electrolysis is an interesting technology, as it may convert the energy supplied by solar cells or wind mills to a storable chemical fuel, which in turn might be utilized to drive environmentally friendly fuel cell devices. However, for this purpose the efficiency of water electrolysis, which is currently about 65 % for alkaline water electrolysis, has to be improved. A main reason for this low efficiency of water electrolysis, is the high ohmic drop in the electrolyte, which is caused by the produced non-conductive hydrogen gas bubbles. Hydrogen bubbles that remain attached to the electrode, where the reduction of protons generates them, block the electrode and thus additionally decrease the efficiency by reducing the effective electrode area. In this project, we aim to increase the water electrolysis efficiency by reducing the negative effects of the formed hydrogen bubbles via application of magnetic fields. These will be generated by simple commercial NdFeB permanent magnets which are known to induce a Lorentz-force-driven Magnetohydrodynamic (MHD) flow around each bubble. This flow acts on different length scales and may enhance the bubble removal from the electrode. This will be studied in this project by means of carefully designed systematic experimental investigations.Electrodes of different electrocatalytic and magnetic properties (Au, Pt, Ni) and variable design will be used to study the electrochemical behavior fundamentally by means of cyclovoltammetry, noise spectra and electrical impedance spectroscopy with respect to nucleation, growth and coalescence of the bubbles. By means of optical microscopy, the growth of hydrogen bubbles will be characterized by measuring e.g. bubble diameter and contact angle versus time until the bubble detaches. In parallel, the MHD swirling flows around the bubbles, will be measured by particle image velocimetry. Particular attention will be paid on how the interaction between the hydrogen bubbles and their associated flow systems will change the detachment compared to single bubbles. Additionally, surface-tension-lowering additives will be added to the electrolyte to further improve the bubble release from the electrode. Also the presumably beneficical impact of magnetic gradient fields on the bubble management will be analysed within this project. The results of electrochemical and optical measurement will be considered in a common context to gain a comprehensive understanding of the magnetic fields effects on water electrolysis.