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- x Sr x (CrMnFeCoNi) 0.2 O 3 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 0.3 Sr 0.7 (CrMnFeCoNi) 0.2 O 3 is only 330 mV at 10 mA cm -2 , achieving a reduction of 120 mV in overpotential compared to La(CrMnFeCoNi) 0.2 O 3 , 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 Cr 6+ , Mn 4+ , Fe 4+ , Co 4+ and Ni 3+ 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.