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

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Perovskite oxides are crucial for developing advanced catalysts and electrodes for energy conversion devices like fuel cells and electrolyzers.
• The double-perovskite oxide PrBa$_{0.5}$Sr$_{0.5}$Co$_{1.5}$Fe$_{0.5}$O$_{5+δ}$ exhibits promising trifunctional catalytic properties.

Purpose of the Study:

• To investigate the trifunctional catalytic properties of PrBa$_{0.5}$Sr$_{0.5}$Co$_{1.5}$Fe$_{0.5}$O$_{5+δ}$ and its composite with silver (Ag).
• To evaluate the performance of the PrBa$_{0.5}$Sr$_{0.5}$Co$_{1.5}$Fe$_{0.5}$O$_{5+δ}$-Ag composite as a catalyst for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR).

Main Methods:

• Glycine nitrate process for synthesizing the PrBa$_{0.5}$Sr$_{0.5}$Co$_{1.5}$Fe$_{0.5}$O$_{5+δ}$-Ag composite.
• Electrocatalytic studies in alkaline solution.
• Electrochemical impedance spectroscopy (EIS) with distribution function of relaxation times (DFRT) analysis.
• Symmetric-cell measurements at high temperatures using oxygen-ion and proton-conducting cells.

Main Results:

• The Ag-based composite demonstrates excellent catalytic activity for both OER and HER in alkaline media.
• EIS and DFRT analyses indicate that improved activity is due to the suppression of resistance from various relaxation processes.
• DFRT studies revealed DC bias dependence of charge-transfer processes, oxygen-surface kinetics, polarization resistances, and activation energies for ORR.
• Ag addition significantly enhances the OER, HER, and ORR kinetics of the PrBa$_{0.5}$Sr$_{0.5}$Co$_{1.5}$Fe$_{0.5}$O$_{5+δ}$ material.

Conclusions:

• The PrBa$_{0.5}$Sr$_{0.5}$Co$_{1.5}$Fe$_{0.5}$O$_{5+δ}$-Ag composite is a highly effective trifunctional catalyst for energy applications.
• Silver addition is a viable strategy to improve the electrocatalytic performance of perovskite oxides for fuel cells and electrolyzers.