Surface Engineering in MgCo₂O₄ Spinel Oxide for an Improved Oxygen Evolution Reaction

Abstract

Spinel-type oxides exhibit great potential for the electrocatalytic oxygen evolution reaction (OER) due to their variable surficial composition and electronic structure. Herein, taking MgCo 2 O 4 as a prototype, we put forward a surface engineering procedure to tailor the surface composition and valence state of cobalt ions for enhancing the OER performance. We discovered that the calcination temperature can finely tailor the ratio of Co/Mg and Co 3+ /Co 2+ on the surface of MgCo 2 O 4 . MgCo 2 O 4 with the maximum ratio of Co 3+ /Co 2+ gives a current density of 10 mA cm −2 at a small overpotential of 283 mV. Such an overpotential is significantly lower than that of most cobaltbased spinel oxides ever reported. X-ray photoelectron spectra demonstrate that increasing the ratio of Co 3+ /Co 2+ plays key roles in improving the OER performance. This work furnishes an instructive idea in pursuit of spinel-type oxides with high OER catalytic activity and stability by surface engineering.

WITHDRAWN: Twofold ion effect to develop PANI@MgCoO2 nanocomposites for magnesium batteries

“…The F 2g peak at roughly 520 cm − 1 , shows the stretching vibration of the Co-O bond. The E g mode at ~ 478 cm − 1 is caused by stretching of Mg-O and Co-O bonds in the tetrahedral sublattice [32]. For the PANI (emeraldine salt), Raman band at 1604 cm − 1 is related to the C-C stretching vibration of benzene ring.…”

A Novel Biomimetic Catalyst with Mn4‐xNixCaO5 Structure for Superior Oxygen Evolution Reaction

“…[44] 3) Favorable electronic state: the introduction of Ni brings a unique synergy effect between Ni and Mn, the opposite valence distribution of Ni and Mn accelerates the electron transfer. [53,54] 4) Low impedance: the small R ct originates from the rich defects and interface structure, which promotes charge transfer. 5) Superior hydrophilic and gas-removing properties: surface Ca 2+ ions lead to good hydrophilic and gas-removing properties, which effectively reduce the hindrance of bubbles to mass and charge transfer, thus promoting the reaction kinetic process and increasing the stability of the catalyst.…”

Cobalt–Magnesium Oxide Catalysts for Deep Oxidation of Hydrocarbons

“…Other studies note the high thermal stability of CoO-MgO solid solutions and their low tendency to coking, which determines their high potential in the dry reforming of methane [12]. Recently, the number of studies on MgCo 2 O 4 spinel has increased in connection with the search for active components and supports for catalysts [24][25][26][27], as well as nanostructured compositions for electrocatalysis [28], thermochemical energy storage cycles [29], and electrodes for Li-ion batteries and supercapacitors [30,31]. However, studies examining the genesis of the Co-Mg oxide system during its heat treatment with the transition of the spinel into the solid solution are few and contradictory [12,31,32].…”