A‐site Cation Defects (Ba_0.5Sr_0.5)_1–xCo_0.8Fe_0.2O_3–δ Perovskites as Active Oxygen Evolution Reaction Catalyst in Alkaline Electrolyte^†

Abstract

Main observation and conclusion Perovskites (Ba0.5Sr0.5)1–xCo0.8Fe0.2O3–δ (x = 0.02, 0.05, 0.1 denoted as BSCF‐0.98, BSCF‐0.95, BSCF‐0.9, respectively) with A‐site cation defects are synthesized by simple and efficient sol‐gel method and are proved to have better OER catalytic effect than the well‐known Ba0.5Sr0.5Co0.8Fe0.2O3–δ (BSCF) oxides. BSCF‐0.95 exhibits the best OER catalytic activity in the series perovskite. The current density of BSCF‐0.95 is about 56% higher than that of BSCF oxide at a potential of 1.7 V. The experimental studies have shown that compared with BSCF, BSCF‐0.95 oxide has a larger electrochemical surface area (ECSA), a higher content of O22– species related to surface oxygen vacancies, and faster charge transfer rate, which may be the factors for the enhancement of OER activity. The theoretical calculation results prove that the center positions of the O 2p‐band of perovskite with A‐site cation defects are closer to the Fermi level than BSCF oxide, which agrees with the OER performance trend of the material.

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

“…For SCF-C and BSCF, the diffraction peaks can be assigned to the cubic phase structures of a = 3.8466 Å and a = 3.9931 Å, respectively (similar to the literature reports). 35,36…”

Promoting nitrate electroreduction to ammonia over A-site deficient cobalt-based perovskite oxides

“…For the (BS) 1− x CF samples, the position of the main peak corresponding to the (110) plane shifted slightly to a higher angle with the increasing A-site cation deficiencies. 30 This indicates lattice shrinkage (Fig. S2†) mainly due to a small amount of BO 6 octahedra tilted toward the extra space of the A-site deficiency or oxygen vacancy.…”

“…The peaks at 528.7, 529.4, 530.9, and 532.8 eV are attributed to lattice O 2− , highly oxidative oxygen species (O 2 2− /O − , corresponding to oxygen vacancies), surface adsorbed O 2 or hydroxyl groups, and surface adsorbed H 2 O, respectively. 30 The relationship between surface oxygen vacancies and A-site cation deficiencies is obtained from the O 1s XPS spectra and iodometric titration (Fig. 2d and Table S4†).…”

Cation Defect Engineering of Transition Metal Electrocatalysts for Oxygen Evolution Reaction

“…The method called the “nonstoichiometric strategy” is normally used to induce A‐site deficiency by changing the proportion of the metal salts when preparing. [ 123–130 ] Controlling the rate of the crystal growth process can also contribute to generating cation vacancies. α‐Ni(OH) 2 with rich Ni cation vacancies was prepared by a rapid hydrolysis rate of Ni 2+ in the presence of less water ( Figure 10 a).…”