Single-particle atomic-scale strain-gradient engineering for high-performance fuel cells.

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Electrochemical energy conversion demands electrocatalysts with precisely controlled active sites.
• Achieving atomic-level control over site-specific reactivity in heterogeneous catalysts is a significant challenge.

Purpose of the Study:

• To introduce and demonstrate atomic-scale gradient strain as a novel design concept for heterogeneous electrocatalysis.
• To spatially link distinct elementary steps of a reaction on a single catalyst particle.

Main Methods:

• Fabrication of Pd@Pt core-shell tetrahedra with 3-4 atomic-layer Pt {111} epitaxial shells.
• Creation of a continuous lattice-strain gradient within individual Pt shells via lattice mismatch.
• Characterization of strain distribution from -8% to -2% across the catalyst surface.

Main Results:

• The strain gradient spatially coordinated O2 activation at highly compressed sites and *OH weakening at moderately compressed sites.
• Achieved competitive oxygen reduction reaction (ORR) performance: 2.19 A mgPt⁻¹ and 3.01 mA cm⁻² at 0.9 V vs RHE.
• Demonstrated high durability with 91% activity retention after 20,000 cycles.

Conclusions:

• Atomic-scale gradient strain is an effective strategy for designing advanced heterogeneous electrocatalysts.
• The engineered catalyst shows promise for applications in fuel cells, achieving high power densities (2.10 W cm⁻² in H2-O2).
• The catalyst maintained over 90% performance after 20,000 cycles in membrane electrode assemblies.