Locking interstitial hydrogen atoms in Pd metallenes for efficient oxygen reduction reaction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Palladium hydride (PdH_x) metallenes are effective electrocatalysts for the oxygen reduction reaction (ORR).
• Their application is limited by the instability of interstitial hydrogen at elevated temperatures (around 353 K).

Purpose of the Study:

• To enhance the stability and performance of palladium hydride metallenes for ORR at high temperatures.
• To investigate the role of manganese (Mn) in stabilizing the PdH_x lattice.

Main Methods:

• Synthesis of palladium-manganese hydride (PdMnH_x) metallenes.
• Electrochemical testing of ORR activity across a temperature range (303-353 K).
• Spectroscopic analyses (e.g., X-ray photoelectron spectroscopy) and theoretical calculations (density functional theory).

Main Results:

• PdMnH_x metallenes exhibit stable and high alkaline ORR performance from 303 K to 353 K.
• At 353 K, PdMnH_x shows a mass activity 14.1 times higher than PdH_x at 0.95 V (1.41 A mg^-1).
• Manganese effectively locks interstitial hydrogen within the Pd lattice, preventing its degradation at high temperatures.

Conclusions:

• Manganese incorporation is crucial for stabilizing PdH_x metallenes for high-temperature ORR.
• The enhanced stability is attributed to strong electronic interactions in the immiscible Pd-Mn alloy, which lock hydrogen.
• PdMnH_x metallenes represent a promising catalyst for demanding ORR applications requiring elevated temperatures.