Low-temperature synthesized amorphous quasi-high-entropy carbonate electrocatalyst with superior surface self-optimization for efficient water oxidation

Anionic High-entropy materials have seldom been reported as a new library of water oxidation electrocatalysts owing to great difficulty in uniformly distributing multiple elements with different physicochemical properties and harsh synthesis conditions. Herein, a series of amorphous quasi-high-entropy carbonates for the first time is prepared via a facile low-temperature hydrothermal route. The optimized CoCrFeMnMoCO3 with hydrothermal treatment of 6 h can serve as a promising oxygen evolution reaction (OER) electrocatalyst for water splitting on account of amorphous structure rendering more exposed active sites, superior synergistic effect realizing surface component self-optimization, high-valence ferritic species (Fe(3+delta)+) providing high catalytic activity and highentropy stabilization guaranteeing long-term OER performance, thus exhibiting the low overpotentials of 302 and 355 mV at the current densities of 10 and 100 mA cm- 2, respectively, the small Tafel slope of 36.7 mV dec-1, and excellent durability longer than 38 h, dramatically exceeding its corresponding crystalline counterpart and benchmark RuO2 catalyst, as well as yielding the current density of 10 mA cm-2 with impressive low voltage of 1.56 V while used as bifunctional electrocatalyst for overall water splitting. This study lights a broad avenue to design other anionic high-entropy materials as promising OER catalysts.