Comparison of the Electrochemical Performances of Solid Oxide Fuel Cells with Sputtered Thin Barrier Layers Fueled by Hydrogen or Ammonia

We investigated the influence of a fuel change from pure hydrogen to a hydrogen-ammonia mixture at different percentages on the electrochemical behavior of 50 mm in diameter Solid Oxide Fuel Cells (SOFCs) with sputtered thin buffer layers of Gd-doped ceria, varying the working temperatures from 800 & DEG;C to 650 & DEG;C. The results show that the performances of the cells are not affected by the fuel change for high working temperatures (800 & DEG;C and 750 & DEG;C). As an example, a power density value of 802 mW & BULL;cm(-2) at 1 A & BULL;cm(-2) is found when directly feeding the cell with 8 NmL & BULL;min(-1)cm(-2) of ammonia and with an equivalent flowrate of 12 NmL & BULL;min(-1)cm(-2) of H-2. These power density output values are higher than those obtained in industrial state-of-art (SoA) SOFCs with screen-printed buffer layers fed with equivalent hydrogen flowrates, thanks to the improved electrochemical performances obtained in the case of cells with sputtered thin buffer layers of Gd-doped ceria. At lower working temperatures (700 & DEG;C and 650 & DEG;C), slight changes in the electrochemical behavior of the cells are observed. Nevertheless, in this temperature range, we also obtain an output current density value of 0.54 A & BULL;cm(-2) in a pure ammonia flowrate of 12 NmL min(-1)cm(-2) at 800 mV and 700 & DEG;C, equal to the value observed in SoA button cells with industrial screen-printed GDC barrier layer fueled with 16 NmL & BULL;min(-1)cm(-2) of H-2. These results pave the way towards the use of innovative SOFC structures with sputtered thin buffer layers fueled by ammonia.