Peroxide Yield of the (001) La 0.6 Sr 0.4 MnO 3 Surface as a Bifunctional Electrocatalyst for the Oxygen Reduction Reaction and Oxygen Evolution Reaction in Alkaline Media (original) (raw)
Related papers
Reversible perovskite electrocatalysts for oxygen reduction/oxygen evolution
Chemical Science, 2019
The identification of electrocatalysts mediating both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are prerequisite for the development of reversible fuel cells and rechargeable metal-air batteries. The question remains as to whether a bifunctional catalyst, or a single catalyst site, will exhibit potentials converging to +1.23 V RHE. Transition metal-based perovskites provide tunable catalysts where site substitution can influence both ORR and OER, however substitution in the pseudobinary phases results in an anti-correlation in ORR and OER activities. We reveal that La x Mn y Ni 1Ày O 3Àd , compositions with lanthanum A-site sub-stoichiometry exhibit reversible activity correlating with the appearance of the Mn 3+ /Mn 4+ redox couple. The Mn 3+ /Mn 4+ couple is associated with Mn 4+ co-existing with Mn 3+ in the bulk, as La 3+ is substituted by Ni 2+ at the A-site to create a mixed valent system. We also show that a direct A-site substitution by the Ca 2+ cation in La x Ca 1Àx Mn y O 3Àd perovskites also results in the creation of Mn 4+ , the appearance of the Mn 3+ /Mn 4+ redox couple, and a concomitant reversible activity. These results highlight a general strategy of optimizing oxide electrocatalysts with reversible activity.
Catalysts, 2022
Perovskite oxides, being transition metal oxides, show promise as bifunctional catalysts being able to catalyze both oxygen evolution reactions (OER) and oxygen reduction reactions (ORR). These two reactions play a crucial role in energy storage and energy conversion devices. An important feature of perovskite catalyst is their ability to be tuned, as tuning can positively affect both reactivity and stability. In this study, Density Functional Theory (DFT) has been utilized to calculate both the equilibrium phase stability and the overpotentials (reactivity performance indicator of the catalysts) of La1−xSrxMnO3 (LSM) structures with different stoichiometry by introducing Mn and O vacancies for both the OER/ORR reactions. The electronic structures reveal that combined Mn and O vacancies can lead to higher catalytic activity for both OER and ORR due to the optimum filling of antibonding orbital electrons. Moreover, both O p-band centers and equilibrium phase stability plots show that...
Physical chemistry chemical physics : PCCP, 2015
In this work, we performed density functional theory (DFT) calculations with inclusion of Hubbard U corrections for the transition metal d-electrons, to investigate stability and electrocatalytic activities of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) for the ABO3 (A = La; B = Cr, Mn, Fe, Co, and Ni) (001) surfaces. We showed surface binding energies of relevant ORR/OER species are coupled strongly to surface polarity and local oxidation states, giving large (∼1 eV scale per adsorbate) differences in binding between (001) AO and BO2 surfaces, where the more oxidized BO2 bare surfaces in general exhibit weak coverage dependence, while the more reduced AO bare surfaces of the LaCrO3, LaMnO3, and LaFeO3 perovskites with lower d-electron filling show strong/moderate coverage dependences. We then predicted that surface coverage can play a key role in determining surface stability, and when coverage effects are included the AO and BO2(001) surfaces have eithe...
Chemically Driven Enhancement of Oxygen Reduction Electrocatalysis in Supported Perovskite Oxides
The journal of physical chemistry letters, 2017
Perovskite oxides have the capacity to efficiently catalyze the oxygen reduction reaction (ORR), which is of fundamental importance for electrochemical energy conversion. While the perovskite catalysts have been generally utilized with a support, the role of the supports, regarded as inert toward the ORR, has been emphasized mostly in terms of the thermal stability of the catalyst system and as an ancillary transport channel for oxygen ions during the ORR. We demonstrate a novel approach to improving the catalytic activity of perovskite oxides for solid oxide fuel cells by controlling the oxygen-ion conducting oxide supports. Catalytic activities of (La0.8Sr0.2)0.95MnO3 perovskite thin-film placed on different oxide supports are characterized by electrochemical impedance spectroscopy and X-ray absorption spectroscopy. These analyses confirm that the strong atomic orbital interactions between the support and the perovskite catalyst enhance the surface exchange kinetics by ∼2.4 times,...
Crystals
The electrocatalytic activity characterization of the oxygen reduction reaction (ORR) is commonly characterized using a rotating disk electrode (RDE) with linear sweep voltammetry (LSV) or cyclic voltammetry (CV) measurements. Despite the wide application of this method in the literature, its reproducibility and comparability are rarely mentioned in articles. LSV and CV are sensitive to experimental conditions, thus the reproducibility is a significant concern. In this article, the perovskite oxides La1−xSrxMnO3 (LSMOx, x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) are chosen for the case study to measure their electroactivity using the RDE method. The main elements that influence the reproducibility of the experiment are presented and the corresponding explanations as well as the means for ensuring the reproducibility are given. Through the case study of LSMOx with variations in x and calcination temperatures, the values for the kinetic current of ORR on different catalysts are compared. It is f...
Chemistry of Materials, 2017
Oxygen electrocatalysis is at the heart of the emerging energy conversion and storage devices including reversible fuel cells and metal-air batteries. However, replacing the noble-metal-based oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts with affordable and robust alternatives remains challenging to date. Herein, we report a cation-ordered double perovskite oxide, i.e., PrBa 0.85-Ca 0.15 MnFeO 5+δ , with excellent stability and activity in both OER and ORR. The layered crystal structure provides ordered oxygen vacancy channels and a vast amount of surface oxygen defects, while the moderate amount of iron dopant keeps the B-site cations at high oxidation state with optimal e g fillings. Importantly, the DFT calculations along with the advanced TEM analysis verify that the incorporation of Ca at the A-site stabilizes the perovskite structure under potential bias. Such a bifunctional catalyst shows comparable, if not better, activity relative to the state-of-the-art perovskite oxides (e.g., Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ) while demonstrating remarkably enhanced robustness. This work presents a rational approach of designing efficient, robust, and cost-effective perovskite oxide for oxygen electrocatalysis and sheds light on the influences of the crystallographic structure on the catalytic property.
Nano-Sized Double Perovskite Oxide as Bifunctional Oxygen Electrocatalysts
Annals of Materials Science & Engineering, 2021
Double perovskite oxide La2Co0.5Fe0.5MnO6-d is synthesized by the moltensalt- assisted method with Nano-sized particles (≈55 nm). The as-obtained La2Co0.5Fe0.5MnO6-d exhibits obviously enhanced electro catalytic activities towards oxygen evolution reaction and oxygen reduction reaction compared to the counterpart La2CoMnO6-d. This work provides a simple method to synthesize Nano-sized double perovskite oxide as superior electro catalysts for energy conversion.
AMnO3 (A = Sr, La, Ca, Y) Perovskite Oxides as Oxygen Reduction Electrocatalysts
Topics in Catalysis, 2018
A series of perovskite-type manganites AMnO 3 (A = Sr, La, Ca and Y) particles were investigated as electrocatalysts for the oxygen reduction reaction. AMnO 3 materials were synthesized by means of an ionic-liquid method, yielding phase pure particles at different temperatures. Depending on the calcination temperature, particles with mean diameter between 20 and 150 nm were obtained. Bulk versus surface composition and structure are probed by X-ray photoelectron spectroscopy and extended X-ray absorption fine structure. Electrochemical studies were performed on composite carbon-oxide electrodes in alkaline environment. The electrocatalytic activity is discussed in terms of the effective Mn oxidation state, A:Mn particle surface ratio and the Mn-O distances.