Co₃O₄ Nanostructures with Different Morphologies and their Field‐Emission Properties

Abstract

We report an efficient method to synthesize vertically aligned Co3O4 nanostructures on the surface of cobalt foils. This synthesis is accomplished by simply heating the cobalt foils in the presence of oxygen gas. The resultant morphologies of the nanostructures can be tailored to be either one‐dimensional nanowires or two‐dimensional nanowalls by controlling the reactivity and the diffusion rate of the oxygen species during the growth process. A possible growth mechanism governing the formation of such nanostructures is discussed. The field‐emission properties of the as‐synthesized nanostructures are investigated in detail. The turn‐on field was determined to be 6.4 and 7.7 V μm–1 for nanowires and nanowalls, respectively. The nanowire samples show superior field‐emission characteristics with a lower turn‐on field and higher current density because of their sharp tip geometry and high aspect ratio.

Co3O4@CeO2 Core@Shell Cubes: Designed Synthesis and Optimization of Catalytic Properties

“…As reported previously, the XPS curve of Co 2p shows two major peaks at 795.5 and 780.4 eV, corresponding to the Co 2p 1/2 and Co 2p 3/2 spin-orbit signals, respectively. [27] As shown in Figure S15 b, there are no clear Co signals in the binding energy range 775-810 eV. However, it is well known that the XPS characterization is only suitable for testing the superficial composition of samples, so the absence of Co peaks and the presence of Ce peaks confirms the core@shell structure of the as-obtained Co 3 O 4 @CeO 2 cubes, in accordance with the SEM and TEM analysis results.…”

Synthesis of 2D/2D Structured Mesoporous Co3O4 Nanosheet/N‐Doped Reduced Graphene Oxide Composites as a Highly Stable Negative Electrode for Lithium Battery Applications

“…The two peaks at 781.8 and 796.6 eV are assigned to the Co 2 + state, whereas two other peaks positioned at 779.5 and 794.5 eV are attributed to the existence of Co 3 + ions. [25][26][27] The spin-orbit splitting is about 14.7 eV which clearly suggest the formation of Co 3 O 4 .T he deconvoluted C1 ss pectrum showedf oura dditional sublevels (Figure 6c). The C1 sp eaks clearly exhibits ac onsiderable degree of oxidation with four components corresponding to various functionalities over carbonaceous materials;t hese include non-oxygenated ring C=Cb onding at 284.6 eV,C ÀOb onding at 286.03 eV,t he carbonyl carbon (C=O) at 287.3 eV,a nd the carboxylate carbon (OÀC=O) at 288.4 eV.T his clearlyi ndicates the presenceo fs urfacef unctional groupso ver carbonaceous materials.…”

Tuning the Morphology of Metal Oxides for Catalytic Applications

“…104 Besides chemical routes in liquid solution, physical techniques and hard-templating methods, such as template directing and electrospinning, have been applied to prepare one-dimensional Co 3 O 4 nanostructures. [105][106][107][108][109][110][111][112][113][114][115][116] Co 3 O 4 nanowires/nanorods can be accomplished by growing on solid substrates, typically involving the reaction of gaseous oxygen molecules with cobalt foil. 105-108 A solution-based route has been developed for the direct growth of freestanding hollow Co 3 O 4 nanowire arrays on a variety of substrates, such as transparent conducting glass, Si wafer, Cu or Ti foil, and polystyrene substrate.…”