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

Abstract

AbstractThe 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 (Gd2O3, Sm2O3, Eu2O3, and CeO2) by using RE metal–organic frameworks to tune the ORR performance of the Pd sites through the Pd−RExOy interface interaction. Taking Pd−Gd2O3/C as a representative, it is identified that the strong coupling between Pd and Gd2O3 induces the formation of the Pd−O−Gd bridge, which triggers charge redistribution of Pd and Gd2O3. The screened Pd−Gd2O3/C exhibits impressive ORR performance with high onset potential (0.986 VRHE), half‐wave potential (0.877 VRHE), and excellent stability. Similar ORR results are also found for Pd−Sm2O3/C, Pd−Eu2O3/C, and Pd−CeO2/C catalysts. Theoretical analyses reveal that the coupling between Pd and Gd2O3 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−Gd2O3 is close to the theoretical optimal activity for ORR, outperforming Pt under the same conditions. By its ascendancy in ORR, the Pd−Gd2O3/C exhibits superior performance in Zn‐air battery as an air cathode, implying its excellent practicability.