Anisotropic Strain Tuning of L1₀ Ternary Nanoparticles for Oxygen Reduction

Abstract

Tuning the performance of nanoparticle (NP) catalysts by controlling the NP surface strain has evolved as an important strategy to optimize NP catalysis in many energy conversion reactions. Here, we present our new study on using an eigenforce model to predict and experiments to verify the strain-induced catalysis enhancement of the oxygen reduction reaction (ORR) in the presence of L1₀-CoMPt NPs (M = Mn, Fe, Ni, Cu, Ni). The eigenforce model allowed us to predict anisotropic (that is, two-dimensional) strain levels on distorted Pt(111) surfaces. Experimentally, by preparing a series of 5 nm L1₀-CoMPt NPs, we could push the ORR catalytic activity of these NPs toward the optimum region of the theoretical two-dimensional volcano plot predicted for L1₀-CoMPt. The best ORR catalyst in the alloy NP series we studied is L1₀-CoNiPt, which has a mass activity of 3.1 A/mg_Pt and a specific activity of 9.3 mA/cm² at room temperature with only 15.9% loss of mass activity after 30 000 cycles at 60 °C in 0.1 M HClO₄.