Gadolinium-induced valence structure engineering for enhanced oxygen electrocatalysis

Rare earth doped materials with unique electronic ground state configurations are considered emerging alternatives to conventional Pt/C for the oxygen reduction reaction (ORR). Herein, gadolinium (Gd)-induced valence structure engineering is, for the first, time investigated for enhanced oxygen electrocatalysis. The Gd₂O₃-Co heterostructure loaded on N-doped graphene (Gd₂O₃-Co/NG) is constructed as the target catalyst via a facile sol-gel assisted strategy. This synthetic strategy allows Gd₂O₃-Co nanoparticles to distribute uniformly on an N-graphene surface and form intimate Gd₂O₃/Co interface sites. Upon the introduction of Gd₂O₃, the ORR activity of Gd₂O₃-Co/NG is significantly increased compared with Co/NG, where the half-wave potential (E_1/2) of Gd₂O₃-Co/NG is 100 mV more positive than that of Co/NG and even close to commercial Pt/C. The density functional theory calculation and spectroscopic analysis demonstrate that, owing to intrinsic charge redistribution at the engineered interface of Gd₂O₃/Co, the coupled Gd₂O₃-Co can break the OOH*-OH* scaling relation and result in a good balance of OOH* and OH* binding on Gd₂O₃-Co surface. For practical application, a rechargeable Zn-air battery employing Gd₂O₃-Co/NG as an air-cathode achieves a large power density and excellent charge-discharge cycle stability.