Manipulating cation nonstoichiometry towards developing better electrolyte for self-humidified dual-ion solid oxide fuel cells

Dual-ion (oxygen ion and proton) conducting electrolyte BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ (BZCYYb) is one of the most commonly used electrolyte materials for proton conducting fuel cells (PCFCs). Here, we improve conducting property and performance of BZCYYb electrolyte through simply introducing B-site cation deficiency. Dual-ion conductivities for Ba(Zr_0.1Ce_0.7Y_0.1Yb_0.1)_0.95O_3-δ (BZCYYb-0.95) electrolyte are improved to a large extent as 2.5 times protonic conductivity (4.6 × 10⁻² S cm⁻¹ at 700 °C) and 6.3 times oxygen ionic conductivity (1.2 × 10⁻² S cm⁻¹ at 900 °C) compared to BZCYYb electrolyte. Low-temperature (1350 °C) sinterability of BZCYYb-0.95 is achieved for the higher concentration of defect compared to the original material (BZCYYb, 1500 °C). Meanwhile, a cell with the BZCYYb-0.95 electrolyte illustrates prominent power density of 794 mW cm⁻² at 650 °C, superior to the cell with BZCYYb (643 mW cm⁻²) at the same condition. The collaborative diffusions of dual-ion via two different conducting mechanisms enhance the cell performance with BZCYYb-0.95 electrolyte. The cell voltage and power density actually have no observable performance degradation during the course of the 300-h test. Therefore, it indicates the dual-ion diffusions of BZCYYb-0.95 electrolyte as the promising future for practical application.