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

ABSTRACT

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 La1-x Sr x (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 La0.3Sr0.7(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.