Tri-Functional Double Perovskite Oxide Catalysts for Fuel Cells and Electrolyzers

Perovskite oxides are at the forefront of the race to develop catalysts/electrodes for fuel cells and electrolyzers. This work presents trifunctional properties of the double-perovskite oxide PrBa_0.5 Sr_0.5 Co_1.5 Fe_0.5 O_5+δ and the PrBa_0.5 Sr_0.5 Co_1.5 Fe_0.5 O_5+δ -Ag composite prepared by the glycine nitrate process. The electrocatalytic studies reveal that the Ag-based composite is an excellent catalyst for both oxygen evolution (OER) and hydrogen evolution reactions (HER) in alkaline solution. The electrochemical impedance spectroscopy analysis through distribution function of relaxation times (DFRT) suggests that the improved activity originates from the suppression of resistance contributed by various relaxation processes. The oxygen reduction reaction (ORR) kinetics in these oxide-based cathodes has been studied by performing symmetric-cell measurements at high temperatures using both oxygen-ion and proton-conducting cells. DC bias dependence of charge-transfer processes, oxygen-surface kinetics, polarization resistances, and activation energies are revealed by DFRT studies. Ag addition in PrBa_0.5 Sr_0.5 Co_1.5 Fe_0.5 O_5+δ leads to enhanced kinetics of OER, HER, and ORR.