Solid Oxide Electrolysis Cells: Degradation at High Current Densities

Abstract

The degradation of Ni/yttria-stabilized zirconia (YSZ)-based solid oxide electrolysis cells operated at high current densities was studied. The degradation was examined at 850°C , at current densities of −1.0, −1.5, and −2.0A/cm2 , with a 50:50 (normalH2O:normalH2) gas supplied to the Ni/YSZ hydrogen electrode and oxygen supplied to the lanthanum, strontium manganite (LSM)/YSZ oxygen electrode. Electrode polarization resistance degradation is not directly related to the applied current density but rather a consequence of adsorbed impurities in the Ni/YSZ hydrogen electrode. However, the ohmic resistance degradation increases with applied current density. The ohmic resistance degradation is attributed to oxygen formation in the YSZ electrolyte grain boundaries near the oxygen electrode/electrolyte interface.

Ni/YSZ electrodes structures optimized for increased electrolysis performance and durability

“…Both Cell A and Cell B experienced a huge increase in the ohmic resistance and this did not seem to level off after several hundred hours of testing, which in turn will be detrimental to the cells. This is much in line with observations reported previously for electrolysis testing at high current densities [6,7,38]. Cell C, on the other hand, have an ohmic resistance development that was significantly different even though these three cells are tested at nominally the same electrolysis test conditions.…”

“…Even though reversible operation of SOC (i.e. fuel cell mode operation) has shown advantageous for the performance of SOC [4,5]; it should be emphasized that at higher electrolysis current densities irreversible degradation phenomena takes place which are not likely to be recoverable by SOFC operation of the SOC [6,7]. Long-term stability needs to be improved even considering promising results such as reported by Tietz, Corre and Hjalmarsson [8][9][10][11] if SOFC systems, and later SOEC systems, are to operate profitable for several years.…”

Evolution of the electrochemical interface in high-temperature fuel cells and electrolysers

“…The process is reversible; anodic polarisation causes Mn diffusion back to LSM and re-oxidizes the Mn ions, restoring the 3PB-dominated reaction zone and its lower electrochemical activity. For LSM and other oxygen-electrodes, applying too high anodic overpotential for long periods of time (when performing electrolysis) causes microstructure degradation at the electrode/electrolyte interface [48][49][50] . The interfacial oxygen pressure, which varies exponentially with the overpotential, can become high enough to precipitate pressurized oxygen bubbles in closed cavities and/or to force oxygen incorporation into the LSM crystal lattice, eventually weakening and cracking the interface.…”

An electrochemical model for syngas production by co-electrolysis of H2O and CO2

“…Compared with alkaline and PEM electrolyzers, SOECs consume less electricity as part of the energy needed for water splitting is in the form of heat [5]. Because of their great potential, SOECs have received increasing interest in recent years [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Various materials have been developed to fabricate SOEC for hydrogen production by steam electrolysis [21][22][23].…”