Durable and Efficient Hollow Porous Oxide Spinel Microspheres for Oxygen Reduction

Abstract

The oxygen reduction reaction performance of the hollow porous oxide spinel microspheres was investigated. The ZnMnCoO 4 possessed a high onset potential of 1.00 V and an outstanding durability in the alkaline solution. The electronic transition of Co 3+ ions was found to weaken the Co 3+ -OH bond and facilitate the O 2À /OH À displacement. Thus, it may offer promising potential for use as an effective catalyst with high oxygen reduction activity and durability in fuel cells and metal-air batteries, among other applications.

Redox‐Inert Fe3+ Ions in Octahedral Sites of Co‐Fe Spinel Oxides with Enhanced Oxygen Catalytic Activity for Rechargeable Zinc–Air Batteries

“…[13,14] Recently,i twas reported that Fe substitution just served as as upportive core element in spinel, which can contribute to the long-term durability. [15] In this work, we present af acile strategy to activate Co 3+ Oct .C o À Ob ond length changes caused by replacement of Co by Fe can also affect the covalencyofthe bond. Moreover,N-doped carbon nanotubes (NCNTs) can act as an ideal conductive substrate for metal oxides,o wing to its high electrical conductivity, large surface area, and intrinsic flexibility.…”

A Phthalocyanine‐Based Layered Two‐Dimensional Conjugated Metal–Organic Framework as a Highly Efficient Electrocatalyst for the Oxygen Reduction Reaction

“…The2 D porous structure ensures fast mass transport while the defined active sites (Ni-N 4 )e ffectively catalyze the ORR. [29,30] Such Co-O x sites effectively promote the breaking of the M-OH À bond as well as the O 2 2À /OH À exchange reaction. [29] Fori nstance,p erovskites (e.g.L aCO 3 )a nd AB 2 O 4 spinel with Co-O x sites with single-electron occupation of the e g orbital of the Co atom show ORR performance comparable to that of platinum-based electrocatalysts.…”

“…[17] Apart from M-N x sites, [28] the catalytic activity of M-O x sites with unique electronic structures is intrinsically high for electrocatalytic ORR. [29][30][31] Therefore,i ncorporating molecular Co-O x structures within the highly conductive 2D conjugated MOFs hints at the promise for achieving superior catalytic ORR activity for fuel cells and metal-air batteries. [29,30] Such Co-O x sites effectively promote the breaking of the M-OH À bond as well as the O 2 2À /OH À exchange reaction.…”

“…[29] Fori nstance,p erovskites (e.g.L aCO 3 )a nd AB 2 O 4 spinel with Co-O x sites with single-electron occupation of the e g orbital of the Co atom show ORR performance comparable to that of platinum-based electrocatalysts. [29,30] Such Co-O x sites effectively promote the breaking of the M-OH À bond as well as the O 2 2À /OH À exchange reaction. [29][30][31] Therefore,i ncorporating molecular Co-O x structures within the highly conductive 2D conjugated MOFs hints at the promise for achieving superior catalytic ORR activity for fuel cells and metal-air batteries.…”

“…[35,38] Importantly,t his phenomenon also suggests that the electronic configuration of Co is relevant to t 2g 6 e g 1 ,which is near the optimal e g filling of 1a nd favorable for high electrocatalytic activity toward ORR. [29,30] Thec hemical states of Co and Cu atoms in PcCu-O 8 -Co were further determined by X-ray absorption near-edge structure (XANES) analysis (Figure 2a). [39][40][41] Cu K-edge spectra of PcCu-O 8 -Co and the monomer {PcCu-(OH) 8 }a re similar and resemble that of the reference compound copper-(II) phthalocyanine (PcCu) since they all have the same common Cu-N motif.These spectra are distinctly different to those of Cu foil and CuO,c onfirming the CuÀNb onding in PcCu-O 8 -Co.I nt he Co K-edge spectra, the pre-edge at 7709 eV originates from the absorption transition from 1s to 3d.…”