Nanoscale Compositionally Graded Thin‐Film Electrolyte Membranes for Low‐Temperature Solid Oxide Fuel Cells

Controllable fabrication of compositionally graded Gd_0.1Ce_0.9O_2‐δ and Y_0.16Zr_0.84O_2‐δ electrolytes using co‐sputtering is demonstrated. Self‐supported membranes were lithographically fabricated to employ the new electrolytes into thin film solid oxide fuel cells. Devices integrating such electrolytes demonstrate performance of over 1175 mW cm^?2 and 665 mW cm^?2 at 520 °C using hydrogen and methane as fuel, respectively. The results present a general strategy to fabricate nanoscale functionally graded materials with selective interfacial functionality for energy conversion.