Shaping triple-conducting semiconductor BaCo(0.4)Fe(0.4)Zr(0.1)Y(0.1)O(3-δ) into an electrolyte for low-temperature solid oxide fuel cells

Interest in low-temperature operation of solid oxide fuel cells is growing. Recent advances in perovskite phases have resulted in an efficient H(+)/O(2-)/e(-) triple-conducting electrode BaCo(0.4)Fe(0.4)Zr(0.1)Y(0.1)O(3-δ) for low-temperature fuel cells. Here, we further develop BaCo(0.4)Fe(0.4)Zr(0.1)Y(0.1)O(3-δ) for electrolyte applications by taking advantage of its high ionic conduction while suppressing its electronic conduction through constructing a BaCo(0.4)Fe(0.4)Zr(0.1)Y(0.1)O(3-δ)-ZnO p-n heterostructure. With this approach, it has been demonstrated that BaCo(0.4)Fe(0.4)Zr(0.1)Y(0.1)O(3-δ) can be applied in a fuel cell with good electrolyte functionality, achieving attractive ionic conductivity and cell performance. Further investigation confirms the hybrid H(+)/O(2-) conducting capability of BaCo(0.4)Fe(0.4)Zr(0.1)Y(0.1)O(3-δ)-ZnO. An energy band alignment mechanism based on a p-n heterojunction is proposed to explain the suppression of electronic conductivity and promotion of ionic conductivity in the heterostructure. Our findings demonstrate that BaCo(0.4)Fe(0.4)Zr(0.1)Y(0.1)O(3-δ) is not only a good electrode but also a highly promising electrolyte. The approach reveals insight for developing advanced low-temperature solid oxide fuel cell electrolytes.