New BaZr0.125Y0.125M0.75O3 (M=Cu, Mn, Ni, Zn, Co, and Fe) cathodes for proton-conducting solid oxide fuel cells

Different transition metals are employed to tune the Y-doped BaZrO3 proton conductor, resulting in the new BaZr0.125Y0.125M0.75O3 (M = Cu, Mn, Ni, Zn, Co, and Fe) compositions as cathodes for proton-conducting solid oxide fuel cells. Only Co and Fe dopants can yield pure phases, whereas the use of other dopants results in impurities. Further experimental studies and first-principles calculations show that using Fe dopant has some advantages over Co-doped material, such as increased oxygen vacancies, lower proton migration energy barriers, and faster proton and oxygen diffusion kinetics. The fuel cell employing the BaZr0.125Y0.125Fe0.75O3 (BZYFe) cathode has a larger fuel cell output than the fuel cell using the BaZr0.125Y0.125Co0.75O3 (BZYCo) cathode. Furthermore, the CO2 adsorption energy on the BZYFe surface is larger than that at the BZYCo surface, indicating that BZYFe has significantly better chemical stability than BZYCo. The long-term stability of the fuel cell demonstrates that the fuel cell with the BZYCo cathode is degrading. In contrast, the BZYFe cell has good operating stability. Given its phase purity, fuel cell performance, and stability, the Fe element is an appropriate dopant for altering BZY and creating a new cathode.