Constructing Active Sites from Atomic‐Scale Geometrical Engineering in Spinel Oxide Solid Solutions for Efficient and Robust Oxygen Evolution Reaction Electrocatalysts

Abstract

Spinel oxides are considered as promising low-cost non-precious metal electrocatalysts for oxygen evolution reaction (OER) due to their desirable catalytic activities and fast kinetics. However, as a result of the structural complexity of spinel oxides, systematic and in-depth studies on enhancing the OER performance of spinel oxides remain inadequate. In particular, the construction of active sites regarding the large number of unoccupied octahedral interstices has not yet been explored. Herein, more octahedral sites with high OER activities are constructed on the surface of spinel oxides via a cationic misalignment, which is induced by the defects in the spinel oxide solutions, i.e., MoFe 2 O 4 and CoFe 2 O 4 nanosheets supported on an iron foam (MCFO NS/IF). With increased active sites and modified electronic structure, the state-of-the-art electrocatalyst exhibits the excellent OER catalytic activity with an onset potential of 1.41 V versus RHE and an overpotential of 290 mV to achieve a current density of 500 mA cm −2 . Moreover, such an electrocatalyst also demonstrates fast kinetics with the Tafel slope of 38 mV dec −1 and superior durability by maintaining the OER activity at 250 mA cm −2 for 1000 h.

Filling Octahedral Interstices by Building Geometrical Defects to Construct Active Sites for Boosting the Oxygen Evolution Reaction on NiFe2O4

“…In our previous report, we created cationic vacancies to induce the reoccupation of octahedral interstices for improving the catalytic activity of OER. [ 15 ] Although this strategy was successfully implemented, the number of octahedral interstices to be refilled was limited. This may be because that the anchoring effect of unsaturated O anions hampers the migration of foreign cations.…”

Hexagonal perovskite Sr6(Co0.8Fe0.2)5O15 as an efficient electrocatalyst towards the oxygen evolution reaction

“…[10][11][12] The kinetics of these reactions are slow, especially for the OER, which is considered to be a key ratelimiting step involving four-electron transfer reactions, requiring high overpotentials to drive the reactions. [13][14][15][16][17] In recent years, the perovskite oxide (ABO 3 ) electrocatalyst has drawn considerable attention due to its compositional and structural flexibility, relatively low price, rich content, and environmental friendliness. [18][19][20] The perovskite oxides show great flexibility in active sites and oxygen vacancies because of the possible substitutions on the A, B, and O sites, which in turn affect the physical/chemical properties and catalytic performance.…”

Water electrolysis: from textbook knowledge to the latest scientific strategies and industrial developments

“…Latest efforts aimed in further incrementing the activity of spinel-based OER electrocatalysts. [779][780][781][782][783][784][785] A nano-scaled oxide hybrid material comprising CoFe 2 O 4 spinel modified by CeO 2 (CeO 2 @CoFe 2 O 4 ) displayed outstanding OER activity in 1 M KOH: a very low overpotential (Z = 213 mV) was enough to reach j = 100 mA cm À2 . 780 A strategy to increase the number of octahedral OER active sites on the surface of spinel oxides was recently shown by Yue et al: 784 a solid solution comprising MoFe 2 O 4 and CoFe 2 O 4 nanosheets supported on iron foam was synthesised through a hydrothermal route + annealing step (Fig.…”