Synergistically\nEnhanced Oxygen Evolution Reaction Catalysis for Multielement Transition-Metal\nOxides

Abstract

Transition\nmetal oxides have been extensively investigated as novel catalysts\nfor oxygen evolution reaction (OER). Partial elemental substitutions\nare effective ways to increase catalytic performance and such electronic\ninteractions between multiple elements are known as synergistic effects.\nHowever, serious issues such as random atomic arrangement and ambiguous\nroles of constituent elements humper theoretical investigations for\nrational materials design. Herein, we describe systematic study on\nOER activity of <i>AA</i>′₃<i>B</i>₄O₁₂-type quadruple perovskite oxides, in which\nmultiple transition metal ions are located at distinct crystallographic\nsites. Electrochemical measurements demonstrate that OER catalytic\nactivities of quadruple perovskite oxide series, CaCu₃<i>B</i>₄O₁₂ (<i>B</i> = Ti, V,\nCr, Mn, Fe, and Co), are all superior to those of simple perovskite\ncounterparts Ca<i>B</i>O₃. The order of activity\nof <i>B</i>-site transition metal ions for Ca<i>B</i>O₃ (Fe⁴⁺ > Co⁴⁺ ≫ Ti⁴⁺, V⁴⁺, Cr⁴⁺, Mn⁴⁺) is retained\nin CaCu₃<i>B</i>₄O₁₂, indicating\nthat <i>B</i>-site ions play a primary role whereas <i>A</i>′-site Cu ions secondarily contribute to OER activity\nfor CaCu₃<i>B</i>₄O₁₂.\nCharge-transfer energies, energy differences between oxygen 2p band\ncenter and unoccupied 3d band center of <i>B</i>-site transition\nmetal obtained from first-principles electronic-state calculations,\nillustrate that OER overpotentials of quadruple perovskite oxides\nare lower than simple perovskite oxides by ∼150 mV. These findings\npropose a simple avenue to realize enhanced OER activity for multiple\ntransition-metal ions.