Effect of the reactive surface area of proton-conducting NiBa0.8Sr0.2Ce0.6Zr0.2Y0.2O3-δ anodes on cell performance

To determine the optimal combination of NiO and Ba0.8Sr0.2Ce0.6Zr0.2Y0.2O3-δ (BSCZY) for fabricating anode materials, Ni-BSCZY samples were prepared using the solid state reaction process. The porous structure of anode substrates not only provides mechanical strength to the fuel cells to enable fuel gases to flow to the electrolyte membrane but also creates an excess surface area on which to form a larger triple-phase boundary when NiO is added to the anode sample. The effect of NiO content on the microstructures, surface area, and electric conductivity of these Ni-BSCZY (NiO55-BSCZY, NiO60-BSCZY, and NiO65-BSCZY) anode materials were systematically investigated using X-ray diffraction, scanning electron microscopy, an analytic technique based on the Brunauer–Emmett–Teller surface area theory, and four-probe conductivity analysis. In addition, three anode-supported cells containing identical electrolytes but various combinations of NiO and BSCZY anode materials were fabricated and used for performance and electrochemical impedance measurement. The results revealed that the reactive surface area of the anode in contact with the electrolyte plays a crucial role in total cell performance. The cell containing the anode material (NiO60-BSCZY) with the highest surface area of 6.91 m2 g−1 and the lowest total resistance of 2.19 Ω cm2 exhibited the highest power density of 169.2 mW cm−2 at 800 °C.