General synthesis of CoCeMO_x trimetallic oxides via a cation exchange reaction for the oxygen evolution reaction

Abstract

Cobalt-based spinel oxides are considered as potential candidates for oxygen evolution reaction (OER) due to their abundant valence changes and promising electrochemical activity, but low intrinsic activity hinders their practical...

Bird Nest-Like Fe3O4/CoOx Nanosphere Heterojunctions with Amorphous/Crystalline Structure for Enhanced Electrochemical Oxygen Evolution

“…When the reaction was extended to 3–6 h, the CoFe-SUCS structure remained almost the same morphology of the sea urchin-like hollow core–shell nanosphere, which is completely different from that of Co-CDSAAs (Figures f–i and S2f–i). Fourier transform infrared (FT-IR) spectroscopy (Figure S3) revealed that their characteristic absorption peaks are almost the same except for the infrared absorption peaks in the fingerprint region, which is different from our report. − This may be the reason for the different morphologies of the CoFe-SUCS and Co-CDSAAs.…”

“…It is evident that the Co species changes to multiple valence states from Co 2+ after CoFe-SUCS was calcined in an Ar/H 2 atmosphere (Figures b and S10a). In the Co 2p spectrum (Figure b), with the presence of satellite peaks at 802.7, 798.8, 786.8, and 785.1 eV, the Co 3+ and Co 2+ fitted peaks of Co 2p 3/2 located at 779.7 and 782.3 eV respectively, and the peaks located at 794.4 and 795.5 eV fitted Co 2p 1/2 orbital, except that a new small signal of Co mental was detected, which confirmed the part reduction process in Ar/H 2 atmosphere. ,− As for Fe 2p orbital regions (Figure c), the spectra show peaks located at 711.3 and 709.6 eV correspond to Fe 3+ and Fe 2+ of Fe 2p 3/2 orbital, respectively. − The reason for the number of fitted peaks in BN-Fe 3 O 4 /CoO x being more than that in CoFe-SUCS could be this: the Co element in CoFe-SUCS assembled through the coordination of Co 2+ with the organic ligand HL 10 resulted in the presence of the fitted peaks of Co 2+ . After the calcination in the reducing gas Ar/H 2 , some Co 2+ is reduced to Co 0 , and the O element in the organic ligand HL 10 can partially oxidize Co 2+ to Co 3+ during the pyrolysis process.…”

“…Oxygen vacancy can lead to the upward shift of Fermi energy level, which is conducive to accelerating the charge transfer, thus promoting the kinetic process of OER. 41 The electrocatalytic activities for the OER are examined in a 1.0 M KOH electrolyte at a scan rate of 5 mV s −1 at room temperature. All catalysts were cyclic voltammetry (CV) cycled to a stable state prior to testing, and not corrected by iRcompensation.…”

“…In this design, cobalt coordination-driven self-assembled aggregates (Co-CDSAAs) are still the precursor as we used before . Ammonium ferrous sulfate, a kind of double salt, has the doping metal source and the etching effect, which replaces the Lewis acid in our previous publications. , Interestingly, an exquisite hollow heterostructure different from that of our published work is formed by calcination eventually. Benefiting from these advantageous features of transition metal doping, a/c heterostructure, and distinct morphology, the BN-Fe 3 O 4 /CoO x nanosphere shows enhanced OER activity and durability in alkaline media.…”

“…Considering these points, with the inspiration of our previous work, − we report a strategy of cation exchange followed by Ar/H 2 annealing to construct a bird nest-like bimetallic OER electrocatalyst with a/c heterostructure nanosphere (BN-Fe 3 O 4 /CoO x ). In this design, cobalt coordination-driven self-assembled aggregates (Co-CDSAAs) are still the precursor as we used before .…”