Anisotropic Strain Tuning of L1 Ternary Nanoparticles for Oxygen Reduction.

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 L1-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 L1-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 L1-CoMPt. The best ORR catalyst in the alloy NP series we studied is L1-CoNiPt, which has a mass activity of 3.1 A/mg and a specific activity of 9.3 mA/cm at room temperature with only 15.9% loss of mass activity after 30 000 cycles at 60 °C in 0.1 M HClO.