Cobalt-Doped Ba₂In₂O₅ Brownmillerites: An Efficient Electrocatalyst for Oxygen Reduction in Alkaline Medium

Abstract

A series of compounds with cobalt doping in the indium site of Ba 2 In 2 O 5 brownmillerites exhibited excellent oxygen reduction activity under alkaline conditions. Doping (25%) retains the brownmillerite structure with disorder in the O3 site in the two-dimensional alternate layer along the ab plane. Further substitution of cobalt in the indium site leads to the loss of a brownmillerite structure, and the compound attains a perovskite structure. Cobalt-doped samples exhibited far better oxygen reduction reaction (ORR) activity when compared to the parent Ba 2 In 2 O 5 brownmillerite. Among the series of compounds, BaIn 0.25 Co 0.75 O 3−δ with the highest Co doping and oxygen vacancies randomly distributed in the lattice exhibited the best ORR activity. BaIn 0.25 Co 0.75 O 3−δ showed a 40 mV positive shift in the onset potential with better limiting current density and a nearly four-electron-transfer reduction pathway when compared to the parent Ba 2 In 2 O 5 brownmillerite.

Visible‐Light‐Driven One‐Pot Synthesis of Benzimidazoles, Benzothiazoles, and Quinazolinones Catalyzed by Scalable and Reusable Ba‐Doped CoMoO4 Nanoparticles Under Air Atmosphere

“…Figure 5d shows the XPS spectra of Ba 3d level. The peak splits into two binding energies of 794.4 and 780.3 eV, corresponding to Ba 3d 3/2 and Ba 3d 5/2 spin states with a splitting width of 15.1 eV [38a] . This reveals that barium is in Ba 2+ state in the nanostructures.…”

Hexagonal Boron Nitride-Supported Crystalline Manganese Oxide Nanorods/Carbon: A Tunable Nanocomposite Catalyst for Dioxygen Electroreduction

“…A Koutecky–Levich (K-L) approach provides kinetic information in the form of the number of electrons transferred ( n ) per oxygen molecule during electroreduction of oxygen. Accordingly, Figure c shows the K-L plot (J –1 vs ω –1/2 ), and the number of electrons transferred to the MnBN/C-75 electrode was calculated using the K-L equation: where where I is the measured current, I k is the kinetic limiting current, I d is the diffusion-limiting current, ω is the rotation rate of RDE, B is the K-L slope, which is determined by using the K-L plot, n is the number of electrons transferred during the ORR process, F is the Faraday constant (96485 C/mol), ν is the kinematic viscosity of the 0.1 M KOH electrolyte (0.01 cm 2 /s), D O 2 is the diffusion coefficient of oxygen (1.9 × 10 –5 cm 2 /s), C O 2 is the bulk concentration of oxygen (1.2 × 10 –6 mol/L), and A is the geometrical surface area of RDE . Usually for the classic Pt-based catalyst, the direct 4-electron transfer oxygen electroreduction is a more favorable pathway (eq ) than initially a 2-electron electrochemical reduction of the O 2 molecule into peroxide (HO 2 – ) followed by instantaneous decomposition of HO 2 – via another 2-electron (eqs and ) for the ORR. , …”

“…is the kinematic viscosity of the 0.1 M KOH electrolyte (0.01 cm 2 /s), D O 2 is the diffusion coefficient of oxygen (1.9 × 10 −5 cm 2 /s), C O 2 is the bulk concentration of oxygen (1.2 × 10 −6 mol/L), and A is the geometrical surface area of RDE. 64 Usually for the classic Pt-based catalyst, the direct 4-electron transfer oxygen electroreduction is a more favorable pathway (eq 5) than initially a 2-electron electrochemical reduction of the O 2 molecule into peroxide (HO 2 − ) followed by instantaneous decomposition of HO 2 − via another 2-electron (eqs 6 and 7) for the ORR. 65,66…”

The effects of sintering atmospheres on piezoelectric performances of Co‐doped Ba0.88Ca0.12Zr0.12Ti0.88O3 ceramics

“…The spin-orbit splitting value of Co 2p 1/2 and Co 2p 3/2 is 15.4, and a satellite structure is observed at approximately 787.5 eV, and both of them indicate the coexistence of Co 3+ and Co 2+ . [22][23][24] The peaks present at 780.2 and 795.6 eV are Co 3+ 2p 3/2 and 2p 1/2 , whereas the peaks existing at 782.5 and 797.9 eV are related to Co 2+ 2p 3/2 and 2p 1/2 . 25 In Figure 1B, the fitting graph of Co ion shows two distinguished peaks with a bonding energy of 781.4 and 796.9 eV, which are assigned to Co 2p 3/2 and Co 2p 1/2 .…”