Potassium-Substituted LaMnO₃ as a Highly Active and Exceptionally Stable Electrocatalyst toward Bifunctional Oxygen Reduction and Oxygen Evolution Reactions

Abstract

Efficient, low-cost, and long-lasting electrocatalysts that accelerate sluggish oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) kinetics are highly desirable for a variety of applications, including metal–air batteries and fuel cells, but they are uncommon. Such bifunctional catalysts are primarily harmed by either low catalytic activity or degradation during prolonged cycling. We devise a relatively low-temperature hydrothermal strategy for producing a perovskite oxide-based catalyst composed of potassium-substituted LaMnO3. In an alkaline environment, the catalyst performs admirably, with improved kinetics and activity for the ORR (half-wave potential of 0.78 V) and OER (potential at the current density of 10 mA cm–2 is 1.66 V). Furthermore, as a two-electrode cell, this catalyst renders the potential for use as an electrode in zinc–air batteries with unprecedented stability (no visible sign of degradation even after 1000 cycles of charge–discharge).

Recent Advances in Manganese-Based Materials for Electrolytic Water Splitting

“…Defect engineering can also optimize the charge distribution around the active site, accelerate the charge transfer rate, and change the morphology and structure of the material. The resulting abundant lattice dislocation and surface vacancy are conducive to the acceleration of the electron transfer and enhancement of the catalytic performance of the OER and the HER [ 66 , 121 , 122 , 123 , 124 , 125 ]. Finally, phase engineering regulates the different morphologies of catalytic materials by changing the reaction temperature.…”

Importance of K Substitution in LaMnO3 Nanostructures for the Selective Reduction of α,β-Unsaturated Carbonyl Compounds and Nitroarenes

“…This La(OH) 3 phase was successfully separated using density-based separation techniques (described in the Supporting Information, SI), as depicted in Figure 2c,d. 8 Using inductively coupled plasma atomic emission spectroscopy (ICP-AES), we analyzed the purity of the LKMO sample in terms of possible residue elements, including chlorides. According to the findings, these contaminants are absent from the final product.…”

“…For decades, lanthanum-based 3d metal perovskite oxides (LMOs) have remained one of the most intriguing classes of materials due to their remarkable properties, such as superconductivity, colossal magnetoresistance, and supercapacitance . In addition to some NO x reductions, the catalytic activity of LMOs and their substitutional analogues is primarily concentrated on oxidative reactions. , They have not been investigated with regard to the selective hydrogenation of α,β-unsaturated carbonyl compounds and nitroarenes.…”

“…Figure c depicts a FESEM micrograph of LKMO microcubes, which are micron-sized cubes prepared by the reported 7-day basic (18 M KOH) hydrothermal treatment of La­(NO 3 ) 3 ·6H 2 O with MnCl 2 ·4H 2 O and KMnO 4 at 265 °C . The typical sizes range from 4.5 to 27.5 μm, with an average size of 12.7 μm.…”

“…The formation of crystalline LKMO and La­(OH) 3 phases in the as-prepared LKMO samples is revealed by SEM and powder XRD analysis (Figure S1a–c). This La­(OH) 3 phase was successfully separated using density-based separation techniques (described in the Supporting Information, SI), as depicted in Figure c,d . Using inductively coupled plasma atomic emission spectroscopy (ICP-AES), we analyzed the purity of the LKMO sample in terms of possible residue elements, including chlorides.…”