High-entropy spinel-structure oxides as oxygen evolution reaction electrocatalyst

Abstract

High-entropy oxides are an upcoming research topic due to their broad range of possible crystal structures and applications. In this work, we want to present the change in the catalytic properties when using different elements to create a high-entropy spinel. Therefore, we used the nebulized-spray pyrolysis to synthesize the high-entropy spinel (Mn0.2Fe0.2Ni0.2Mg0.2Zn0.2)3O4 and later on exchanged the Mg or the Zn with elements with multiple possible oxidation states, in our example each with Cr or Co. The phase purity, morphology, microstructure and homogeneity were investigated by XRD, SEM and STEM-EDX. Their electrocatalytic performance and stability was measured via oxygen evolution reaction and cyclic voltammetry and compared to IrO2, used as reference. The best performance of the synthesized materials was achieved by (Mn0.2Fe0.2Ni0.2Mg0.2Cr0.2)3O4.

Sol‐Gel‐Derived Ordered Mesoporous High Entropy Spinel Ferrites and Assessment of Their Photoelectrochemical and Electrocatalytic Water Splitting Performance

“…[1] Entropy-induced structure stabilization is also reported to be the reason for improved OER stability in comparison to binary and ternary materials possessing-at the same time-equal overpotentials. [15,66] Stenzel et al identified an optimized elemental composition for spinelstructured HEOs resulting in low overpotentials of 293 mV (at 10 mA cm −2 ). [66] With respect to HEOs, photocatalytic hydrogen production, [67] photoelectrochemical water reduction [23] and oxidation [68] have rarely been studied, showing up to date only low to moderate photocurrents and hydrogen evolution efficiencies.…”

“…[15,66] Stenzel et al identified an optimized elemental composition for spinelstructured HEOs resulting in low overpotentials of 293 mV (at 10 mA cm −2 ). [66] With respect to HEOs, photocatalytic hydrogen production, [67] photoelectrochemical water reduction [23] and oxidation [68] have rarely been studied, showing up to date only low to moderate photocurrents and hydrogen evolution efficiencies. A recent study of our group on (non-ordered) mesoporous spinel HEO revealed a low photoresponse under visible light irradiation, most likely owing to structural defects induced by implementation of several cations with distinct radii.…”

“…[ 1 ] Entropy‐induced structure stabilization is also reported to be the reason for improved OER stability in comparison to binary and ternary materials possessing—at the same time—equal overpotentials. [ 15,66 ] Stenzel et al. identified an optimized elemental composition for spinel‐structured HEOs resulting in low overpotentials of 293 mV (at 10 mA cm −2 ).…”

Sol-gel-derived Ordered Mesoporous High Entropy Spinel Ferrites and Assessment of their Photoelectrochemical and Electrocatalytic Water Splitting Performance

“…[1] The entropy-induced structure stabilization effect is also reported to be the reason for improved OER stability in comparison to binary and ternary materials possessing -at the same time -equal overpotentials. [68,69] In this context, Stenzel et al identified an improved (equiatomic) elemental composition for spinel-structured HEOs resulting in low overpotentials of 293 mV (at 10 mA/cm 2 ). [69] High entropy ferrites (HEF) have recently been investigated as highperforming sulfur host material in lithium-sulfur batteries, [70] as microwave absorbing material, [71,72] and magnetic insulator, [73] however, up to now, never in the context of electrocatalytic and/or photoelectrochemical water splitting.…”

“…[68,69] In this context, Stenzel et al identified an improved (equiatomic) elemental composition for spinel-structured HEOs resulting in low overpotentials of 293 mV (at 10 mA/cm 2 ). [69] High entropy ferrites (HEF) have recently been investigated as highperforming sulfur host material in lithium-sulfur batteries, [70] as microwave absorbing material, [71,72] and magnetic insulator, [73] however, up to now, never in the context of electrocatalytic and/or photoelectrochemical water splitting. Recently, the group of Brezesinski has reported on mesoporous ferrite films as well, however incorporating fewer types of cations and focusing on magnetic properties.…”