The influence mechanism of alkali metal salt potassium carbonate enrichment on NiO/YSZ anode of SOFC

The content of low-melting alkali metals in biomass is relatively high, resulting in alkali metal vapor in the gasification gas. In the biomass gasification integrate with solid oxide fuel cell system, the alkali metals will enrich on anode in long term operation, which will affect the discharge performance. In this work, multiple loads by the aqueous solution are used to simulate the enrichment process of potassium carbonate on the NiO/YSZ anode surface. The results show that a light potassium carbonate load can improve the peak power density of the solid oxide fuel cell. But the peak power density of the cell gradually decreases with the load time increasing higher than twice. Through electrochemical impedance spectroscopy, it is found that the second potassium carbonate loads reduced the polarization impedance from 0.69 Ω·cm² to 0.45 Ω·cm². But no obvious change of ohmic resistance is observed, indicating potassium carbonate loads affect anode catalytic reaction. Through scanning electron microscopes and X-ray diffractometer characterization, it can be concluded that a light potassium carbonate load can reduce the grain size of nickel and improve the anode three-phase boundaries, which leads to the improvement of cell peak power density.