Importing Antibonding‐Orbital Occupancy through Pd−O−Gd Bridge Promotes Electrocatalytic Oxygen Reduction

Abstract The active‐site density, intrinsic activity, and durability of Pd−based materials for oxygen reduction reaction (ORR) are critical to their application in industrial energy devices. This work constructs a series of carbon‐based rare‐earth (RE) oxides (Gd 2 O 3 , Sm 2 O 3 , Eu 2 O 3 , and CeO 2 ) by using RE metal–organic frameworks to tune the ORR performance of the Pd sites through the Pd−RE x O y interface interaction. Taking Pd−Gd 2 O 3 /C as a representative, it is identified that the strong coupling between Pd and Gd 2 O 3 induces the formation of the Pd−O−Gd bridge, which triggers charge redistribution of Pd and Gd 2 O 3 . The screened Pd−Gd 2 O 3 /C exhibits impressive ORR performance with high onset potential (0.986 V RHE ), half‐wave potential (0.877 V RHE ), and excellent stability. Similar ORR results are also found for Pd−Sm 2 O 3 /C, Pd−Eu 2 O 3 /C, and Pd−CeO 2 /C catalysts. Theoretical analyses reveal that the coupling between Pd and Gd 2 O 3 promotes electron transfer through the Pd−O−Gd bridge, which induces the antibonding‐orbital occupancy of Pd−*OH for the optimization of *OH adsorption in the rate‐determining step of ORR. The pH‐dependent microkinetic modeling shows that Pd−Gd 2 O 3 is close to the theoretical optimal activity for ORR, outperforming Pt under the same conditions. By its ascendancy in ORR, the Pd−Gd 2 O 3 /C exhibits superior performance in Zn‐air battery as an air cathode, implying its excellent practicability.