Activating Pd by morphology tailoring for oxygen reduction.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Palladium (Pd) is investigated as an alternative catalyst to platinum (Pt) for the oxygen reduction reaction (ORR).
• Modifying Pd's electronic structure can yield catalytic activity comparable to Pt.
• Structure-activity relationships of Pd catalysts for ORR are not well understood.

Purpose of the Study:

• To investigate the dependence of Pd catalyst activity for ORR on its morphology.
• To explore the potential of Pd nanorods (Pd-NRs) as efficient ORR electrocatalysts.

Main Methods:

• Electrochemical deposition of Pd to control morphology (nanoparticles vs. nanorods).
• Electrochemical experiments, including CO stripping voltammetry.
• Density Functional Theory (DFT) calculations.

Main Results:

• Pd nanorods (Pd-NRs) exhibit a 10-fold higher surface-specific activity for ORR compared to Pd nanoparticles (Pd-NPs).
• Pd-NRs demonstrate catalytic activity comparable to Pt at fuel cell cathode operating potentials.
• Pd-NRs expose Pd(110) facets, which are identified as the active sites for superior ORR performance.

Conclusions:

• Pd morphology significantly impacts ORR activity, with nanorods outperforming nanoparticles.
• The superior activity of Pd-NRs is attributed to the weak interaction of oxygen adatoms on Pd(110) facets.
• This study provides insights into Pd catalysis and offers criteria for designing efficient ORR catalysts.