Precise Strain Tuning Boosts Electrocatalytic Hydrogen Generation

Strain engineering has been utilized as an effective approach to regulate the binding of reaction intermediates and modify catalytic behavior on noble metal nanocatalysts. However, the continuous, precise control of strain for a depiction of strain-activity correlation remains a challenge. Herein, Pd-based nanooctahedrons coated with two Ir overlayers are constructed, and subject to different postsynthetic treatments to alter the amount of H intercalated into Pd core for achieving three different surface strains (o-Pd/Ir-1.2%, o-Pd/Ir-1.7%, and o-Pd/Ir-2.1% NPs). It is demonstrated that the catalytic performances of o-Pd/Ir NPs display a volcano-shaped curve against strains toward the hydrogen evolution reaction (HER). Specifically, o-Pd/Ir-1.7% NPs exhibit superior catalytic performance with a mass activity of 9.38 A mg_Ir ^-1 at -0.02 V versus reversible hydrogen electrode, 10.8- and 18.8-fold higher than those of commercial Pt/C and Ir/C, respectively, making it one of the most active HER electrocatalysts reported to date. Density function theory calculations verify that the moderate tensile strain on Ir(111) surfaces plays a pivotal role in optimizing the H binding energy. This work highlights a new strategy for precise control over the surface strain of nanocrystals for more efficient electrocatalysis.