Boosting the Electrocatalytic Activity of Co₃O₄ Nanosheets for a Li-O₂ Battery through Modulating Inner Oxygen Vacancy and Exterior Co³⁺/Co²⁺ Ratio

Abstract

Rechargeable Li-O2 batteries have been considered as the most promising chemical power owing to their ultrahigh specific energy density. But the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) result in the high overpotential (~1.5V), the poor rate capability and even the short cycle life, which critically hinder their practical applications. Herein, we propose a synergistic strategy to boost the electrocatalytic activity of Co3O4 nanosheets for Li-O2 battery by tuning the inner oxygen vacancies and the exterior Co 3+ /Co 2+ ratio which have been identified by Raman spectroscopy, X-ray photoelectron spectroscopy and X-ray Absorption Near Edge Structure spectroscopy. Operando X-ray diffraction and ex-situ Scanning Electron Microscope are used to probe the evolution of the discharge product. In comparison with bulk Co3O4, the cells catalyzed by Co3O4 nanosheets show a much higher initial capacity (~24051.2mAh g -1 ), better rate capability (8683.3mAh g -1 @400mA g -1 ) and cycling stability (150 cycles@400mA g -1 ), and lower overpotential. The large enhancement of the electrochemical performances can be greatly attributed to the synergistic effect of the architectured 2D nanosheets, the oxygen vacancies and Co 3+ /Co 2+ difference between the surface and the interior.Moreover, the addition of LiI in the electrolyte can further reduce the overpotential making the battery more practical. This study offers some insights into designing high performance electrocatalysts for Li-O2 batteries through the combination of the 2D nanosheets architecture, oxygen vacancy and surface electronic structure regulation.

Simultaneous Modulation of Composition and Oxygen Vacancies on Hierarchical ZnCo2O4/Co3O4/NC‐CNT Mesoporous Dodecahedron for Enhanced Oxygen Evolution Reaction

“…[8] As imilars trong band at 198 cm À1 is observed in Table S2 in the Supporting Information). Upon increasing the temperature, the Zn/Co ratio gradually decreases, which indicates ah igh degree of volatilization of nanosizedZ na th igher temperature;t his is also consistent with TXRF results ( Table S1 in [8,52] The O A /O L ratio increases with the introduction of Zn, the linear sweep voltammetry (LSV) curves, for which 50 mA cm À2 was chosen as an indicator due to the rapid rising current for the oxidation of Co 3 + to Co 4 + at about 1.5 V. [21] /NC-CNT-X could play more criticalr oles in activation of the catalytic sites by decreasingt he adsorption energy of H 2 Om olecules onto the active sites, andt hus, leading to an increasei nt he OER activity. [54,56] DFT calculations have suggestedt hat the existence of oxygen vacancies could decrease the hindrance of the adsorption of H 2 O/OH À at low-coordination Co 3 + sites.…”

“…The HR N 1 s XPS results can be deconvoluted into three peaks located at 398.7, 399.8, and 401.6 eV (Figure S6 D in the Supporting Information), which can be assigned to pyridinic N, pyrrolic N, and quaternary N, respectively. The O 1 s spectrum (Figure S6 E in the Supporting Information) displays two oxygen states at around 529.9 and 531.5 eV, which are related to lattice oxygen bound to metals (O L ) and oxygen vacancies on the surface (O A ) . The O A /O L ratio increases with the introduction of Zn, which indicates a higher concentration of vacancies.…”

“…Amongt hese materials, cobalt-based oxides have exhibited excellent OER performance in the improvement of reactionk inetics andm inimization of the overpotential in the electrolysis process. [1][2][3][4][5][6][7][8][9][10][11][12] Generally,e lemental doping,i ntegration with con-ductive substrates, and open architectures are effective strategies to further increaset heir intrinsic activity and accessible active sites. [2,5,[13][14][15] Different doping at the surface/interface or homogenous metal mixing provides the possibility of tuning the inherent electronic and/or surface structures of the host material.…”

Self‐Supported ZIF‐Derived Co3O4 Nanoparticles‐Decorated Porous N‐Doped Carbon Fibers as Oxygen Reduction Catalyst

“…[49,54] Recently,C o 3 O 4 has been extensivelys tudied and applieda s the cathode catalysti nL i-O 2 battery due to its excellent catalytic activity in non-aqueous electrolyte. [23,35,55] As can be known from the above-mentionedr esultso fT GA/DSC, ZIF-Co 3 O 4 /NCF has ah igh content of Co 3 O 4 .T herefore, in this work, the combination of Co 3 O 4 and N-doped carbon fibre enable the composite catalyst to work in both aqueous and non-aqueous solution.T he ORR activity of ZIF-Co 3 O 4 /NCF in non-aqueous electrolyte was confirmed by performing steadystate staircase voltammetry measurement in O 2 -saturated 0.1 m LiPF 6 in 1,2-dimethoxyethane. As shown in Figure S11, no plateau can be achieved at the low potentialr ange for the both catalysts, which is differentf rom the polarizations in the aqueous electrolyte.…”

Design and Synthesis of Cobalt‐Based Electrocatalysts for Oxygen Reduction Reaction

“…Besides, it is effective strategy to enhance the electrocatalytic activity of cobalt oxide catalysts by adjusting the exterior Co 3+ /Co 2+ ratio. Liu et al . boosted the electrocatalytic activity of Co 3 O 4 nanosheets through modulating inner oxygen vacancy and exterior Co 3+ /Co 2+ ratio, which had been identified by Raman spectroscopy, X‐ray photoelectron spectroscopy, and X‐ray absorption near edge structure spectroscopy.…”