Selectivity of Mixed Iron-Cobalt Spinels Deposited on a N,S-Doped Mesoporous Carbon Support in the Oxygen Reduction Reaction in Alkaline Media

Abstract

One of the practical efforts in the development of oxygen reduction reaction (ORR) catalysts applicable to fuel cells and metal-air batteries is focused on reducing the cost of the catalysts production. Herein, we have examined the ORR performance of cheap, non-noble metal based catalysts comprised of nanosized mixed Fe-Co spinels deposited on N,S-doped mesoporous carbon support (N,S-MPC). The effect of the chemical and phase composition of the active phase on the selectivity of catalysts in the ORR process in alkaline media was elucidated by changing the iron content. The synthesized materials were thoroughly characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy (RS). Detailed S/TEM/EDX and Raman analysis of the phase composition of the synthesized ORR catalysts revealed that the dominant mixed iron-cobalt spinel is accompanied by minor fractions of bare cobalt and highly dispersed spurious iron oxides (Fe2O3 and Fe3O4). The contribution of individual phases and their degree of agglomeration on the carbon support directly influence the selectivity of the obtained catalysts. It was found that the mixed iron-cobalt spinel single phase gives rise to significant improvement of the catalyst selectivity towards the desired 4e− reaction pathway, in comparison to the reference bare cobalt spinel, whereas spurious iron oxides play a negative role for the catalyst selectivity.

The Roles of Composition and Mesostructure of Cobalt‐Based Spinel Catalysts in Oxygen Evolution Reactions

“… [8] In addition they showed the influence of composition and especially phase purity for the selectivity and activity of mixed iron cobalt spinels. [9] Using systematic cation substitution and tuning of the catalysts mesostructure with constant cation ratios, we herein exploit and extend this powerful approach to different oxygen evolving reactions.…”

Operando EPR Study of Radical Formation in Anion-Exchange Membrane Fuel Cells

“…We specifically employed Pd, Ag, PdAg, and (MnCo) 3 O 4 as cathode catalysts to investigate the potential of oxygen radicals formed in different classes of catalysts. These catalysts are chosen as they have relatively high activities as cathodes in AEMFCs, − ,− and they are significantly different.…”

“…Anion-exchange membrane fuel cells (AEMFCs) are regarded as a promising fuel cell technology because of their significant potential to replace the current expensive proton-exchange membrane fuel cell (PEMFC). − Recently, AEMFCs achieved remarkable power densities − with high voltage efficiencies, which makes the technology a serious contender for matured PEMFCs. Additionally, AEMFCs provide the opportunity to incorporate platinum group metal (PGM)-free − catalysts into the electrodes, as well as a greater variety of low-cost polymers for use as membranes . In spite of these benefits, major challenges still need to be addressed before this technology can be utilized in practical applications.…”

CoP nanoparticles embedded in three-dimensional porous network-like structured N, O co-doped carbon nanofibers as an effective bi-functional electrocatalyst for rechargeable zinc–air batteries

“…Researchers have found that heteroatoms, such as N, P, S, O, B and so on, can significantly improve the electronic conductivity and electrocatalytic activity due to the altered electroneutrality and asymmetry of charge distribution around adjacent carbon atoms. [11][12][13][14] For example, due to the high electronegativity of oxygen, O-doping has been widely demonstrated to effectively tune the electronic structure of carbon and thus activate its electrocatalytic activity. [15][16][17] The current study shows that combining metal-based electrocatalysts with O-doped graphite layers can further improve the electrocatalytic activity.…”