Porous calcium–manganese oxide microspheres for electrocatalytic oxygen reduction with high activity

Abstract

A series of calcium-manganese oxides (Ca-Mn-O) were prepared through thermal decomposition of carbonate solid-solution precursors and investigated as electrocatalysts for oxygen reduction reaction (ORR). The synthesized crystalline Ca-Mn-O compounds, including perovskite-type CaMnO 3 , layered structured Ca 2 Mn 3 O 8 , post-spinel CaMn 2 O 4 and CaMn 3 O 6 , presented similar morphologies of porous microspheres with agglomerated nanoparticles. Electrochemical results, surface analysis, and computational studies revealed that the catalytic activities of Ca-Mn-O oxides, in terms of onset potential, reduction current, and transferred electron number, depended strongly on both the surface Mn oxidation state and the crystallographic structures. Remarkably, the as-synthesized CaMnO 3 and CaMn 3 O 6 exhibited considerable activity and enabled an apparent quasi 4-electron oxygen reduction with low yield of peroxide species in alkaline solutions, suggesting their potential applications as cheap and abundant ORR catalysts.

Nitrogen-Doped Mesoporous Graphene as a Synergistic Electrocatalyst Matrix for High-Performance Oxygen Reduction Reaction

“…The data were fitted by the equivalent circuit model and the corresponding Nyquist plots were depicted in Figure 2d. The results showed that N-MG modified electrode had a lower charge transfer resistance (R ct ) value of 51 Ω than that for MG modified electrode (357 Ω), indicating that N-MG exhibited higher electrical conductivity for the electron transfer between Fe(CN) 6 3−/4− and the electrode. Most likely, the higher degree of graphitization in N-MG is related to the better conductivity.…”

“…All ORRs were examined in 0.1 M KOH saturated with O 2 (or N 2 for comparison) at RT. Electrochemical impedance spectroscopy (EIS) was carried out in 10 mM of Fe(CN) 6 −3/−4 solution at open circuit potential by AutoLab PGSTST 30 analyzer (Metrohm Autolab B.V., Switzerland) over a frequency range from 10 5 to 10 −1 Hz with a single modulated AC potential of 10 mV. EIS data were analyzed and fitted by using NOVA 1.7.…”

Oxygen reduction reaction activity of LaMn1-xCoxO3-graphene nanocomposite for zinc-air battery

“…With the shake-up peak considered, the Mn 2p 3/2 peak is separated into two peaks at about 641.0 and 642.3 eV, corresponding to Mn (III) and Mn (IV), respectively [34]. Due to the coexistence of Mn (III) and Mn (IV), cation redox reaction, surface charge storage as well as electronic and ionic properties are feasible to be enhanced [35].…”

Spinel MnCo2O4 and Spinel-Nanocarbon Hybrids as Bifunctional Catalysts for Alternating Oxygen Reduction and Evolution Reactions

“…Mixed-valent transition-metal oxides with spinel structure, particularly cobalt-based spinel oxides, are excellent candidates as alternative bifunctional catalysts due to the high abundance, ease of preparation and outstanding redox stability in aqueous alkaline solutions [12][13][14]. Additionally, the variable valence states and the structural flexibility of the spinel offer great opportunities to fine-tune their catalytic properties [15,16].…”