Enhancement of Electrocatalytic Activity as a Function of Structural Order in Perovskite Oxides

Abstract

Electrocatalytic splitting of water is a promising method of hydrogen generation. Here, we report an enhanced electrocatalytic performance for water electrolysis, achieved through a progressive increase in the ordering of oxygen vacancies in the structural network of oxides. In transition from Sr2FeCoO6−δ (disordered) to CaSrFeCoO6−δ (ordered) and Ca2FeCoO6−δ (highly ordered), the change in the average ionic radius of the A-site metals leads to an increase in the concentration and ordering of oxygen vacancies, resulting in a progressive enhancement of the electrocatalytic activity for both cathodic and anodic half-reactions of water splitting, i.e., hydrogen-evolution (HER) and oxygen-evolution (OER) reactions. The OER electrocatalysis is particularly important, as it is considered the bottleneck for water electrolysis. These electrocatalysts show better activity than the precious metal catalyst RuO2. In contrast to most bifunctional catalysts reported to date, these catalysts can be used in bulk form, without the need for nanofabrication, composite formation, or any additional processing. Density functional theory calculations indicate that the vacancy order leads to a shift of the electronic bands toward the Fermi level. We propose that the ordering of oxygen vacancies can be used as a handle for the design of highly active electrocatalysts.

La-Doped Alumina, Lanthanum Aluminate, Lanthanum Hexaaluminate, and Related Compounds: A Review Covering Synthesis, Structure, and Practical Importance

“…The application in thermal barrier coatings was also considered, whereby layered perovskites of so-called Ruddlesden–Popper structure have an exceptional low thermal conductivity . Chemical, − combustion-, ,− environmental, , , − photo-, , and electrocatalysis − are other areas of potential use. , , − Electrocatalysis includes high-temperature solid-oxide electrolysis cells and water splitting. − Photocatalysis includes water splitting ,− and CO 2 conversions . Emery et al performed a computational screening of perovskites for the solar-driven thermochemical splitting of water, resulting in 139 promising candidates.…”

Transition Metal‐based Perovskite Oxides: Emerging Electrocatalysts for Oxygen Evolution Reaction

“…They are of the form ABO 3 type where A is a larger cation generally lanthanoids or rare earth metals with 12 fold coordination and B is a smaller cation having 6 fold geometry coordinated with six face-centered oxygen (O) anions. [13] Earth's crust contains various types of perovskites and approximately 90 % of the metallic elements of the periodic table can exist in perovskite form which may fulfill the demand for abundant and low-cost materials. The B-site position in perovskites is perfectly held by transition metal elements owing to their special electron configuration and multivalency.…”

Structure Effect on Pseudocapacitive Properties of A2LaMn2O7 (A = Ca, Sr)

“…In recent years, our group has studied various properties of perovskite‐related oxides, [ 10–15 ] including pseudocapacitive properties. [ 7,8 ] In the present study, we demonstrate the change in pseudocapacitive properties as a function of structural symmetry in two materials with perovskite‐related structures.…”

“…For example, perovskite oxides with cubic, tetragonal, orthorhombic, and hexagonal structures have been investigated in an attempt to examine the effect of structure on pseudocapacitance. [9] In recent years, our group has studied various properties of perovskite-related oxides, [10][11][12][13][14][15] including pseudocapacitive properties. [7,8] In the present study, we demonstrate the change in pseudocapacitive properties as a function of structural symmetry in two materials with perovskite-related structures.…”