Demonstrating the dual functionalities of CeO2–CuO composites in solid oxide fuel cells

Nowadays, lowering the operating temperature of solid oxide fuel cells (SOFCs) is a major challenge towards their widespread application. This has triggered extensive material studies involving the research for new electrolytes and electrodes. Among these works, it has been shown that CeO 2 is not only a promising basis of solid oxide electrolytes, but also capable of serving as a catalytic assistant in anode. In the present work, to develop new electrolytes and electrodes for SOFCs based on these features of CeO 2 , a new type of functional composite is developed by introducing semiconductor CuO into CeO 2 . The prepared composites with mole ratios of 7:3 (7CeO 2 –3CuO) and 3:7 (3CeO 2 –7CuO) are assessed as electrolyte and anode in fuel cells, respectively. The cell based on 7CeO 2 –3CuO electrolyte reaches a power outputs of 845 mW cm −2 at 550 °C, superior to that of pure CeO 2 electrolyte fuel cell , while an Ce 0.8 Sm 0.2 O 2-δ electrolyte SOFC with 3CeO 2 –7CuO anode achieves high power density along with open circuit voltage of 1.05 V at 550 °C. In terms of polarization curve and AC impedance analysis, our investigation manifests the developed 7CeO 2 –3CuO composite has good electrolyte capability with a hybrid H + /O 2− conductivity of 0.1–0.137 S cm −1 at 500–550 °C, while the 3CeO 2 –7CuO composite plays a competent anode role with considerable catalytic activity , indicative of the dual-functionalities of CeO 2 –CuO in fuel cell. Furthermore, a bulk heterojunction effect based on CeO 2 /CuO pn junction is proposed to interpret the suppressed electrons in 7CeO 2 –3CuO electrolyte. Our study thus reveals the great potential of CeO 2 –CuO to develop functional materials for SOFCs to enable low-temperature operation.