One challenge facing the development of high-performance cathodes for solid oxide fuel cells is the slow oxygen reduction kinetics due to the limitations of one single material. Here, we report...

A novel redox-stable efficient perovskite anode by bismuth doping for solid oxide fuel cells.

Double perovskite PrBaFe 2 O 5+δ is a potential electrode material for symmetrical solid oxide fuel cells (Sym-SOFCs). This work aims to improve the Sym-SOFC performance by partially replacing Fe with W, forming a composition of (PrBa) 0.95 (Fe 0.95 W 0.05 ) 2 O 5+δ . Doping W keeps PrBaFe 2 O 5+δ stability after high-temperature treatment in both air and hydrogen atmospheres, decreases the thermal expansion coefficient from 17.11 × 10 −6 to 14.59 × 10 −6 K −1 , increases the content of oxygen species that are essential for the electrocatalytic reactions, and increases the chemical oxygen surface exchange coefficient by 121% at 800 °C. Consequently, doping W greatly improves the electrochemical performance, such as decreasing the areaspecific cathode polarization resistance by 35.5% to 0.031 Ω•cm 2 at 800 °C, reducing the anode polarization resistance by 17.7% to 0.123 Ω• cm 2 , and increasing the peak power density of Sym-SOFCs by 32.5% to 1.02 W cm −2 using humidified hydrogen as the fuel. The performance is much higher than those reported for Sym-SOFCs using PrBaFe 2 O 5+δ doped with the other elements. Finally, the Sym-SOFCs are capable of directly using hydrocarbon fuels, providing peak power densities of 0.610, 0.624, and 0.448 W cm −2 at 800 °C for syngas, ethane, and propane, respectively.

No abstract

Double perovskite oxide PrBaFe 2 O 5+δ is a potential cathode material for intermediate-temperature solid oxide fuel cells. To improve its electrochemical performance, the trivalent element Ga is investigated to partially replace Fe, forming PrBaFe 2−x Ga x O 5+δ (PBFGx, x = 0.05, 0.1, and 0.15). The doping effects on physicochemical properties and electrochemical properties are analyzed regarding the phase structures, element valence states, amount of oxygen vacancies, content of oxygen species, oxygen surface exchange coefficients (k chem ), electrochemical polarization resistance, and single-cell performance. Specifically, PBFG0.1 exhibits improved k chem, such as a 19% improvement from 4.09 × 10 −4 to 4.86 × 10 −4 cm s −1 at 750 °C, due to the increased concentration of reactive oxygen species and oxygen vacancies. Consequently, the interfacial polarization resistance is decreased by 28% from 0.057 to 0.041 Ω cm 2 at 800 °C. The subreaction steps of the oxygen reduction reaction in the PBFG0.1 cathode are further investigated, which suggests that the oxygen dissociation process is greatly enhanced by doping Ga. Meanwhile, doping Ga increases the peak power density of the anode-supported single cell by 36% from 629 to 856 mW cm −2 at 800 °C. The single cell with the PBFG0.1 cathode also exhibits good stability in 100 h of long-term operation at 750 °C.