Laves phase Ir 2 Sm intermetallic nanoparticles as a highly active electrocatalyst for acidic oxygen evolution reaction.

Rare earth (RE) intermetallic nanoparticles (NPs) are significant for fundamental explorations and promising for practical applications in electrocatalysis. However, they are difficult to synthesize because of the unusually low reduction potential and extremely high oxygen affinity of RE metal-oxygen bonds. Herein, intermetallic Ir 2 Sm NPs were firstly synthesized on graphene as a superior acidic oxygen evolution reaction (OER) catalyst. It was verified that intermetallic Ir 2 Sm is a new phase belonging to the C15 cubic MgCu 2 type in the Laves phase family. Meanwhile, intermetallic Ir 2 Sm NPs achieved a mass activity of 1.24 A mg Ir -1 at 1.53 V and stability of 120 h at 10 mA cm -2 in 0.5 M H 2 SO 4 electrolyte, which corresponds to a 5.6-fold and 12-fold enhancement relative to Ir NPs. Experimental results together with density functional theory (DFT) calculations show that in the structurally ordered intermetallic Ir 2 Sm NPs, the alloying of Sm with Ir atoms modulates the electronic nature of Ir, thereby reducing the binding energy of the oxygen-based intermediate, resulting in faster kinetics and enhanced OER activity. This study provides a new perspective for the rational design and practical application of high-performance RE alloy catalysts.