Abstract
In this work, mesoporous Ni–Co composite oxides were synthesized by a facile liquid-precipitation method without the addition of surfactant, and their ability to catalyse a low temperature CO oxidation reaction was investigated. To explore the effect of the synergetic interaction between Ni and Co on the physicochemical properties and catalytic performance of these catalysts, the as-prepared samples were characterized using XRF, XRD, LRS, N2-physisorption (BET), SEM, TEM, XPS, H2-TPR, O2-TPD and in situ DRIFTS characterization techniques. The results are as follows: (1) the doping of cobalt can reduces the size of NiO, thus massive amorphous NiO have formed and highly dispersed on the catalyst surface, resulting in the formation of abundant surface Ni2+ ions; (2) Ni2+ ions partially substitute Co3+ ions to form a Ni–Co spinel solid solution, generating an abundance of surface oxygen vacancies, which are vital for CO oxidation; (3) the Ni0.8Co0.2 catalyst exhibits the highest catalytic activity and a satisfactory stability for CO oxidation, whereas a larger cobalt content results in a decrease in activity, suggesting that the amorphous NiO phase is the dominant active phase instead of Co3O4 for CO oxidation; (4) the introduction of Co can alter the morphology of catalyst from plate-like to flower-like and then to dense granules. This morphological variation is related to the textural properties and catalytic performance of the catalysts. Lastly, a possible mechanism for CO oxidation reaction is tentatively proposed.
Highlights
Carbon monoxide is a major atmospheric pollutant
Mesoporous Ni–Co composite oxides were synthesized by a facile liquid-precipitation method without the addition of surfactant, and their ability to catalyse a low temperature carbon monoxide (CO) oxidation reaction was investigated
This study focuses on: (1) investigating the effects of Co doping on textural properties, morphology, chemical composition, redox properties and catalytic performance of NiO; (2) studying the surface structure and structure–activity correlation of the Ni–Co catalysts for low temperature CO oxidation; (3) and analysing the interaction of CO or/and O2 over typical samples by in situ DRIFTS, to reveal a possible reaction mechanism for CO oxidation
Summary
Nickel oxide is an earth-abundant transition metal oxide with superior redox property, electrochemical performance and gas sensing property. Ni–Co materials obtained by different synthetic methods have demonstrated modi ed catalytic performance and stability in various elds including CO and CO2 methanation,[19,20] propane oxidation,[21] reforming reactions[22,23] and as an electrode material.[24] Yu et al.[19] have revealed that the synergetic effect between Ni and Co over bimetallic catalysts can reduce nickel size to enhance the metal particle dispersion and accelerate the activation of adsorbed CO, thereby improving the catalytic activity and coke resistance. This study focuses on: (1) investigating the effects of Co doping on textural properties, morphology, chemical composition, redox properties and catalytic performance of NiO; (2) studying the surface structure and structure–activity correlation of the Ni–Co catalysts for low temperature CO oxidation; (3) and analysing the interaction of CO or/and O2 over typical samples by in situ DRIFTS, to reveal a possible reaction mechanism for CO oxidation
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