Effect of Ni–GDC anode thickness by Co-sputtering on the high-performance thin film solid oxide fuel cells on a nanoporous substrate for low-temperature operation

Thin film solid oxide fuel cells (TF–SOFCs) having Ni–GDC anodes with different thicknesses of (1–5) μm were fabricated on a nanoporous substrate termed anodic aluminum oxide (AAO) for low-temperature operation. By combining the co-sputtering method and the glancing angle deposition method, an ideal anode nanostructure with excellent porosity and electrical conductivity was successfully deposited. The cell showed a high performance of 494.9 mW/cm² at 500 °C having a three μm thick anode. Proper balancing of electronic property and ionic property of the anode results in improved performance of 40.1% over the previously reported cells of similar architectures. Structural, chemical, and electrochemical analyses unveiled the correlation between the electrochemical performance and the anode thin film structure. In particular, the electronic and ionic characteristics of the anode were separated and intensively analyzed with the help of additional methods such as 4-probe sheet resistance measurement and the distribution of relaxation time process with electrochemical impedance spectroscopy data. Through this, the influences of anode thin film thickness on electrical conductivity and fuel diffusion at the nanostructured anode and further on each resistance characteristic were identified, and its comprehensive understanding was gained.