Thermal Activiation of Sr₃Fe₂O₇ Electrocatalysts for Water Oxidation at Neutral pH

Abstract

The Ruddlesden-Popper-type layered perovskite strontium ferrite (Sr3Fe2O7) was studied as an electrocatalyst for water oxidation to molecular oxygen (O2). The electrocatalytic activity of Sr3Fe2O7 was found to be dependent on the temperature, and the overpotential for water oxidation was markedly lower at 70 oC than at 30 oC. Namely, at pH 7, O2 evolution initiated with overpotentials of approximately 100 and 300 mV at 70 and 30 oC, respectively. When lanthanum-substituted Sr3Fe2O7, Sr2.6La0.4Fe2O7, was used to catalyze O2 evolution, the distinctive temperature dependence disappeared and O2 evolution was driven with a low overpotential even at 30 oC. These results suggest that the formation of Fe4+ is important for decreasing the overpotential for water oxidation to produce O2.

Detection of Intermediate Species in Oxygen Evolution on Hematite Electrodes Using Spectroelectrochemical Measurements

“…They found that CaCu 3 Fe 4 O 12 had superior activity to state-of-the-art catalysts such as RuO 2 and Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3‑δ . In addition, we demonstrated that the availability of Fe 4+ significantly affected OER activity of strontium ferrite (Sr 3 Fe 2 O 7 ) derivatives, which contain Fe 4+ but suffer from charge disproportionation (2Fe 4+ → Fe 3+ + Fe 5+ ) at room temperature . When we suppressed the consumption of Fe 4+ owing to this reaction by increasing the temperature or introducing a dopant element, its OER activity considerably increased.…”

Thermal suppression of charge disproportionation accelerates interface electron transfer of water electrolysis

“…Sr 3 Fe 2 O 7 and SrFeO 3 powders were synthesized by a solid-state reaction using α-iron oxide and strontium carbonate as precursors ( 33 , 34 ). A stoichiometric mixture of α-iron oxide (α-Fe 2 O 3 , Shanghai Aladdin Biochemical Technology Co., Ltd., 99.8%) and strontium carbonate (SrCO 3 , Bide Pharmatech Ltd., 99%) was fully ground and spread out in an alumina crucible.…”

The use of strontium ferrite perovskite as an oxygen carrier in the chemical looping epoxidation of ethylene

“…So far, most of the studies focusing on strontium ferrites have used one material alone, viz. SrFeO3- [4,14] or Sr3Fe2O7- [15,16]. In this study, we propose a simple preparation method that results in a mixture of the two perovskite phases.…”