High Configuration Entropy Activated Lattice Oxygen for O₂ Formation on Perovskite Electrocatalyst

Abstract

The single-phase oxides with elemental complexity and compositional diversity, usually named high entropy oxides, feature homogeneously dispersed multi-metallic elements in equiatomic concentration. The unusual properties of high entropy oxides endow their potential application in clean-energy-related electrocatalysis. However, the possible fundamental relationship between configuration entropy and the underlying catalytic mechanism is still not well understood and established. Herein, a high entropy perovskite cobaltate consisting of five equimolar metals in the B-site (Mg, Mn, Fe, Co, and Ni) is employed as an electrocatalyst for oxygen evolution reaction (OER). The configuration entropy serves as an effective tool to promote the intrinsic activity of the Co reactive site and manipulate the OER mechanism. The high entropy cobaltate demonstrates a lower overpotential of 320 mV at a current density of 10 mA cm −2 , outperforming other counterparts. The X-ray spectroscopies disclose the synergistic charge-exchange effect among different cations and the formation of a new oxygen hole state. Combinatorially computational and experimental results unveil the enigma that the high configuration entropy leads to the random occupation of cations, facilitates the surface reconstruction, and benefits the formation of stable surface oxygen vacancies. Owing to these merits, the O 2 formation is found to be kinetically favorable via the lattice oxygen mechanism.

Recent Advances on Perovskite Electrocatalysts for Water Oxidation in Alkaline Medium

“…Yifei Sun et al prepared high-entropy perovskite samples with the B site composed of five isomolar metals, namely Mg, Mn, Fe, Co, and Ni, and the high-entropy perovskite showed better catalytic activity than those of ternary and quaternary configuration entropy and IrO 2 . 131 Theoretical calculation results show that the theoretical overpotential of the LOM on the binary surface is 1.15 V, while high-entropy perovskite oxides have lower overpotential (0.58 V) and smaller transition state energy barrier (0.39 V). Therefore, the OER is more likely to be conducted by the LOM on the surface of a high-entropy catalyst, which is consistent with experimental data.…”

“…La­(CrMnFeCo 2 Ni)­O 3 exhibits excellent OER catalytic activity due to the best Mn 4+ /Mn 3+ ratio (1.55) and the highest oxygen vacancy content. Yifei Sun et al prepared high-entropy perovskite samples with the B site composed of five isomolar metals, namely Mg, Mn, Fe, Co, and Ni, and the high-entropy perovskite showed better catalytic activity than those of ternary and quaternary configuration entropy and IrO 2 . Theoretical calculation results show that the theoretical overpotential of the LOM on the binary surface is 1.15 V, while high-entropy perovskite oxides have lower overpotential (0.58 V) and smaller transition state energy barrier (0.39 V).…”

“…The unique structural characteristics of perovskite-based catalysts allow for surface reconstruction of catalyst during the OER. ,,,, The key to the high catalytic activity of perovskite catalysts is due to the generated hydroxide layer on the surface during the OER. In addition, the enhanced catalytic activity can also be attributed to the interaction between the hydroxide layer and catalyst surface.…”

A high entropy oxide as high-activity electrocatalyst for water oxidation

“…For example, rich magnetic properties are available through an increase in the number of microstates available to the macroscopic system, 24 and the mixed oxygen-transition metal orbital character and covalency of the employed electronic states allows further fine-tuning of the adsorption energies and charge transfer characteristics, [25][26][27] or even an oxygen-related active site for electrocatalysts. 28 Accordingly, HEOs already showed high promise as battery electrodes 29 and as (electro-)catalysts. [30][31][32] The realm of HEOs was extended to perovskite oxides in 2018, 22,33 which offer combining the promising properties and catalytic performance of high-entropy materials with the established high-activity platform of transition metal perovskite oxides.…”

“…[30][31][32] The realm of HEOs was extended to perovskite oxides in 2018, 22,33 which offer combining the promising properties and catalytic performance of high-entropy materials with the established high-activity platform of transition metal perovskite oxides. Despite very recent first accounts on HEO perovskite OER electrocatalysts, 28,34 the electrocatalytic activity has not yet been systematically explored and separated from complex morphologies resulting from the employed synthesis methods or from self-assembly of oxide layers at the solid/liquid interface. 19,20,34,35 As the Jaramillo, Nørskov, Rossmeisl and Markovic groups argued already in 2011 and 2017, the comparison of intrinsic activity across multiple compositions should be performed on identical sample geometries and ideally on single crystalline surfaces.…”