Reducing Critical Raw Material Use in Commercial Solid Oxide Fuel Cells Using Vertically Aligned Thin‐Film Cathodes with Enhanced Long‐Term Stability

Solid oxide fuel cells (SOFCs) are widely presented as a sustainable solution to future energy challenges. Nevertheless, solid oxide fuel cells presently rely on significant use of several critical raw materials to enable optimized electrode reaction kinetics. This challenge can be addressed by using thin‐film electrode materials; however, this is typically accompanied by complex device fabrication procedures as well as poor mechanical/chemical stability. In this work, we conduct a systematic study of a range of promising thin‐film electrode materials based on vertically aligned nanocomposite (VAN) thin films. We demonstrate low area specific resistance (ASR) values of 0.44 cm 2 at 650 °C can be achieved using (La 0.60 Sr 0.40 ) 0.95 Co 0.20 Fe 0.80 O 3 ‐(Sm 2 O 3 ) 0.20 (CeO 2 ) 0.80 (LSCF‐SDC) thin films, which are also characterized by a low degradation rate, approximately half that of planar LSCF thin films. We then integrate these (La 0.60 Sr 0.40 ) 0.95 Co 0.20 Fe 0.80 O 3 ‐(Sm 2 O 3 ) 0.20 (CeO 2 ) 0.80 vertically aligned nanocomposite films directly with commercial anode supported half cells through a single‐step deposition process. The resulting cells exhibit peak power density of 0.47 W cm −2 at 750 °C, competitive with 0.64 W cm −2 achieved for the same cells operating with a bulk (La 0.60 Sr 0.40 ) 0.95 Co 0.20 Fe 0.80 O 3 cathode, despite 99.5% reduction in cathode critical raw material use. By demonstrating such competitive performance using thin‐film cathode functional layers, this work also paves the way for further cost reductions in solid oxide fuel cells, which could be achieved by likewise applying thin‐film architectures to the anode functional layer and/or current collecting layers, which typically account for the greatest materials cost in solid oxide fuel cell stacks. Therefore, the present work marks a valuable step towards the sustainable proliferation of solid oxide fuel cells.