Abstract
In-situ investigations of structural transitions during the thermal-oxidative event of mixed-metal spinel oxide precursors, the so-called nickel- (NCO) and zinc-containing (ZCO) cobaltite spinel precursors, were investigated to understand the formations of the derived NiCo2O4 and ZnCo2O4 spinel oxides, respectively. In-situ XRD investigation revealed that emerged temperatures for spinel oxide phase were between 325 and 400 °C, depending on the cationic substituent. It indicated that the emerged temperature correlated with the absolute octahedral site preference energy (OSPE) of those cations that participated in the development of the spinel framework. Moreover, the incorporated nickel and zinc in the precursors was beneficial for inhibiting the occurrence of the undesired CoO phase. Time-resolved X-ray absorption spectroscopic (TRXAS) data suggested the local structure rearrangement of nickel and zinc throughout the calcination process, which differed from the behavior of single-metal cobalt system. The essential information reported herein provides a benefit to control the cationic distribution within spinel materials, leading to the tunable physical and chemical properties.
Highlights
Cobaltite spinel oxide (CoCo2O4, or Co3O4) has gained great interest as a material with high potential for energy storage, magnetic, and chemical catalytic applications [1,2,3]
In-situ X-ray diffraction (XRD) profiles in Figure 1 illustrate the transformation of the cobaltite spinel precursors (CCO) precursor toward cobalt oxide product by the elevating temperature from room temperature (RT) toward 475 ◦C
The interesting information concerning structural and phase transformation for nickel- (NCO), zinc-containing (ZCO), and undoped cobaltite spinel precursors (CCO) along the thermal-oxidative conversion was revealed by in-situ XRD and time-resolved X-ray absorption (TRXAS) techniques
Summary
Cobaltite spinel oxide (CoCo2O4, or Co3O4) has gained great interest as a material with high potential for energy storage, magnetic, and chemical catalytic applications [1,2,3]. The cobaltite spinel framework can accommodate other first-row transition metals (such as nickel, copper, and zinc) as the substituents, leading to a variety of mixed-metal spinel derivatives [8,9,10,11,12]. In this aspect, the ZnCo2O4 and NiCo2O4 mixed-metal spinels are the major derivatives of cobalt-based spinels. The ZnCo2O4 and NiCo2O4 mixed-metal spinels are the major derivatives of cobalt-based spinels Both materials have significantly attracted extensive consideration in the energy storage field regarding their remarkable electrochemical activities [6,13,14,15,16]. A suitable synthesis condition which could lead to a production of high purity mixed-metal spinel oxides on a large scale is necessary to serve their future demand
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