Tuning the high-entropy perovskite as efficient and reliable electrocatalysts for oxygen evolution reaction

Due to their unique electronic structure, atomic arrangement and synergistic effect, high-entropy materials are being actively pursued as electrocatalysts for oxygen evolution reaction (OER) in water splitting. However, a relevant strategy to improve high-entropy materials is still lacking. Herein, substitutional doping on the La-site in high-entropy perovskite La_1- Sr (CrMnFeCoNi)_0.2O₃ is reported as an efficient OER catalyst. Sr doping is found to be crucial to enhancing the OER activity. The overpotential for the best catalyst La_0.3Sr_0.7(CrMnFeCoNi)_0.2O₃ is only 330 mV at 10 mA cm^-2, achieving a reduction of 120 mV in overpotential compared to La(CrMnFeCoNi)_0.2O₃, which is attributed to the enhancement in intrinsic catalytic activity. Experimental evidences including in situ electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) indicate Sr doping induces the formation of high-valence Cr⁶⁺, Mn⁴⁺, Fe⁴⁺, Co⁴⁺ and Ni³⁺ species, which can accelerate the faster charge transfer at the interface, thereby increasing the intrinsic catalytic activity. The assembled two-electrode overall water splitting system operates stably at 10 mA cm^-2 for 200 h without attenuation. This work offers an important method for developing a high-performance, high-entropy perovskite OER catalyst for hydrogen production by electrochemical water splitting.