Defects‐Induced In‐Plane Heterophase in Cobalt Oxide Nanosheets for Oxygen Evolution Reaction

Abstract

and usually needs large overpotential to proceed, which seriously impedes the commercial application of these electrochemical energy devices. At present, noble metal catalysts, such as RuO 2 and IrO 2 , are generally regarded as the best electrocatalysts for OER. However, high cost, limited resources, and poor stability make them hard to satisfy the requirement of commercial demands. Thus, it's of extreme urgency to develop effective, cheap, and stable OER electrocatalysts.Spinels, which are briefly described as AB 2 O 4 (where metal ions A 2+ bond with O anions to form tetrahedrons and metal ions B 3+ bond with O anions to form octahedrons), [5] have attracted much attention as OER electrocatalysts because of low cost, rich resources and good stability in alkaline solution. However, the electrochemical activities of spinels are restricted by the limited number of reactive sites, little electrical conductivity, and poor intrinsic activity. Therefore, numerous strategies have been applied to improve electrochemical OER activities of metal oxide such as combining with conductive supports, [6] doping with other elements, [7] controlling facet phase, [8] incorporating vacancies, [9] and designing nanostructures. [10] In these strategies, constructing heterophase interface, which can inherit both functions of two different phases and accelerate electron transfer at interface with rapid reaction progress, is an extremely effective method to enhance the activity of electrocatalysts. [11,12] For example, Liu and co-workers have synthesized Pd@PdO 2 @Co 3 O 4 nanocubes to www.advancedsciencenews.com

Optimal Geometrical Configuration of Cobalt Cations in Spinel Oxides to Promote Oxygen Evolution Reaction

“…The Nyquist plots of MgCo 2 O 4 , CoCr 2 O 4 , Co 2 TiO 4 , and Co 3 O 4 were shown in the Supporting Information, Figure S25 b. The equivalent circuit in the Supporting Information, Figure S26 was used to fit the measured electrochemical response . Co 2 TiO 4 exhibits the biggest R ct (2.00 kΩ) and MgCo 2 O 4 exhibits the smallest R ct (158 Ω; Supporting Information, Figure S27).…”

Principles of Water Electrolysis and Recent Progress in Cobalt‐, Nickel‐, and Iron‐Based Oxides for the Oxygen Evolution Reaction

“…The surface area, crystal structure, and electronic structure and consequently the OER performance of cobalt oxides can be also tuned via post-treatment methods. Liu et al [102] reported that heterophase Co 3 O 4 /CoO nanosheets prepared via Ar-plasma etching on Co 3 O 4 could decrease the overpotential up to 92 mV. DFT calculations revealed that the phase transformation of Co 3 O 4 spinel into the CoO rocksalt phase is followed by lattice Co diffusion which causes oxygen vacancy.…”

Recent advances in defect electrocatalysts: Preparation and characterization

“…Notably, the recently developed plasma etching technique is one of the most effective methods to obtain various defects in carbon or metal composite nanomaterials as a high efficiency electrocatalyst by controlling the source of the gas, power level and the etching duration [11,32,33,36,90,[95][96][97][98][99][100][101][102][103][104][105][106]. For example, our group designed an oxygen vacancy defect Co 3 O 4 material with more Co 2+ sites using plasma etching [36].…”