Effect of initial heating rate on thin-film solid oxide fuel cell

Abstract

Thin-film solid oxide fuel cells supported on nano-porous anodic aluminum oxide substrates were fabricated by sequential sputtering methods. Cells were initially heated by three levels of heating rates (10 °Cmin-1, 30 °Cmin-1 and 50 °Cmin-1) from room temperature to the operating temperature of 450 °C. Grain growth of the electrolyte thin film was observed at the faster initial heating rate

average grain sizes were measured by 13.09 nm (10 °Cmin-1), 25.92 nm (30 °Cmin-1) and 89.87 nm (50 °Cmin-1), respectively. Growth of Pt clusters of cathode was followed by grain growth of supporting electrolyte surface, resulting in the reduction of porosity and triple phase boundary. Cell performance was significantly decreased by slowed cathodic reaction kinetics originated from the grain growth of thin-film electrolyte surface and reduction of triple phase boundary. Faradaic area-specific resistance was almost doubled at the 50 °Cmin-1 of initial heating to the cell, compared to 10 °Cmin-1 heated cell. Annealing electrolyte before the deposition of cathode layer enhanced the crystallinity and interfacial stability with the cathode. As a result, increase of faradaic impedance by fast initial heating was significantly reduced.