Isolating Coupled Effects by Interface Editing of Intermetallic Heterostructures for Fuel Cells

Area of Science:

• Materials Science
• Nanotechnology
• Catalysis
• Electrochemistry

Background:

• Heterostructured nanomaterials (i-HS) offer enhanced catalytic properties due to interface interactions.
• Understanding the specific contributions of ligand and strain effects in i-HS remains challenging due to fabrication limitations.
• Developing model systems to isolate these coupled effects is crucial for rational design.

Purpose of the Study:

• To develop a programmable synthesis strategy for intermetallic heterostructures (i-HS) with controlled interfaces.
• To systematically investigate the distinct roles of ligand and strain effects on catalytic activity.
• To optimize i-HS for high-performance anion exchange membrane fuel cells (AEMFCs).

Main Methods:

• An interdiffusion-controlled atomic replacement strategy was employed to synthesize two distinct i-HS systems: Janus hexagonal nanoplatelets (JHPs) and core-crown hexagonal nanoplatelets (CHPs).
• The PdTe||PdBi JHPs system was designed to isolate ligand effects with a coherent heterointerface.
• The Pd20Te7||PdBi CHPs system was engineered with lattice distortion to explore strain effects.
• Oxygen reduction reaction (ORR) activity was systematically analyzed for both systems.
• The best-performing CHP material was fabricated into a membrane electrode assembly for AEMFC testing.

Main Results:

• Both JHPs and CHPs exhibited volcano-shaped activity trends in ORR.
• The Pd20Te7||PdBi CHPs with 31 at.% Bi loading and 4.1% lattice mismatching showed superior catalytic performance compared to JHPs with 62 at.% Bi loading.
• This indicates that strain effects provide a more significant enhancement than ligand effects for optimizing catalysis.
• The optimized CHP-based AEMFC achieved a peak power density of 1.37 W cm⁻² and a specific power of 27.4 W mgPd⁻¹, surpassing current state-of-the-art.
• Exceptional long-term durability was demonstrated with negligible power loss after 100 hours of operation.

Conclusions:

• Strain effects play a dominant role in enhancing catalytic activity in these intermetallic heterostructures.
• The developed programmable synthesis platform enables precise interface engineering for i-HS.
• This work provides critical insights for designing advanced heterostructure systems for catalysis and energy conversion technologies, particularly in AEMFCs.