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.
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