Amorphization of LaCoO₃ Perovskite Nanostructures for Efficient Oxygen Evolution

Abstract

It has become a challenge to further enhance the electrocatalytic performance of perovskite oxides due to their limited active surface area. Herein, we propose a top-down strategy for the amorphization of crystalline LaCoO3 nanopowders with significantly enhanced specific surface area and electrocatalytic oxygen evolution reaction (OER) activity and durability, in which the overpotential at the current density of 10 mA cm–2 reduced from 405 to 293 mV, and the Tafel slope decreased from 96.6 to 63.4 mV dec–1. This work provides an effective method for the property optimization of nanometer perovskite oxides and the design of high-performance electrocatalysts.

Fe-Doped Metal Complex (LaCo0.9Fe0.1O3) and g-C3N4 Formed a Nanoheterojunction for the Photocatalytic Decomposition of Water

“…There is also a satellite peak at 717.9 eV . From Table , we can see that with Fe doping, the ratio of M 2+ /M 3+ increases, enriching oxygen vacancies (OVs) and suppressing direct electron–hole recombination . In short, the XPS results further demonstrate that LaCo 0.9 Fe 0.1 O 3 /g-C 3 N 4 composites were successfully obtained and that the main electron transfer pathway was from LaCo 0.9 Fe 0.1 O 3 to g-C 3 N 4 .…”

“…Through a large number of tests, we can prove that Fe is successfully doped and increases the oxygen vacancy. Our study found that the band gap of LaCo x Fe 1– x O 3 after Fe doping is smaller, the specific surface area is reduced, and the ratio of M 2+ /M 3+ is increased by X-ray photoelectron spectroscopy (XPS) testing, with the introduction of oxygen defects . This reduces the direct recombination of electron–hole pairs and effectively suppresses photogenerated electron–hole pair recombination .…”

“…For example, LaCoO 3 perovskite has attracted wide attention due to its excellent properties and its invention applications including photocatalytic water splitting hydrogen production catalysts, sensors, electromagnetic wave absorption, solid oxide fuel cells, and so forth. − However, its wide band gap, small specific surface area, and fast electron–hole complexation are unfavorable for hydrogen precipitation reactions. By modulating the metal cation or valence state at the B-site while increasing the number of oxygen defects, the catalytic activity of the catalyst can be modulated efficiently. , One of the most studied methods is to replace part of the B-site “Co” with iron. Tang and Wan , reported that Fe-doped nanostructures can be used for efficient electrochemical water splitting for hydrogen production with a hydrogen yield of 6.06 L min –1 g –1 .…”

The Multifunctionality of Lanthanum–Strontium Cobaltite Nanopowder: High-Pressure Magnetic Studies and Excellent Electrocatalytic Properties for OER

“…It is associated with the amorphization of the LSCO-900 surface and the appearance of chemical defects due to a positive core-level shift of 0.4−1.2 eV. 35 Figure 10c shows Sr 3d spectra, which exhibit two main components from the perovskite lattice-bound Sr lat at binding energies of 131.6 eV (Sr 3d 5/2 ) and 133.4 eV (Sr 3d 3/2 ) for LSCO-900 before electrocatalysis. In addition, a shoulder with higher binding energies of 135.2 eV from surface Sr surf is also presented, which is usually associated with surface strontiumrich phases often observed for LSCO materials.…”

“…However, the high electrocatalytic activity of perovskites for OER in an alkaline medium is primarily the result of the redox behavior of the hybridization of transition metal 3d and oxygen 2p orbits . Numerical studies of perovskites as electrocatalysts revealed that, in addition to the chemical composition, activity in oxygen electrocatalysis reactions is also affected by a significant number of factors, namely, method and conditions of preparation of the material (annealing at different temperatures and in a controlled atmosphere can cause different types of defects on the surface); , particle size, porosity, and shape (affects active surface area); − , doping; ,,,, and amorphization of the surface …”