• Benjaram M Reddy

      Articles written in Journal of Chemical Sciences

    • Facile synthesis of catalytically active CeO2-Gd2O3 solid solutions for soot oxidation

      D Naga Durgasri T Vinodkumar Benjaram M Reddy

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      CeO2-Gd2O3 oxides were synthesized by a modified coprecipitation method and subjected to thermal treatments at different temperatures to understand their thermal behaviour. The obtained samples were characterized by XRD, BET, TEM, Raman and TPR techniques. Catalytic efficiencies for oxygen storage/release capacity (OSC) and soot oxidation were evaluated by a thermogravimetric (TG) method. XRD and Raman results indicated the formation of Ce0.8Gd0.2O$_{2−\delta}$ (CG) solid solutions at lower calcination temperatures, and TEM studies confirmed nanosized nature of the particles. Raman studies further confirmed the presence of oxygen vacancies and lattice defects in the CG sample. TPR measurements indicated a facile reduction of ceria after Gd3+ addition. Activity studies revealed that incorporation of Gd3+ into the ceria matrix favoured the creation of more structural defects, which accelerates the oxidation rate of soot compared to pure ceria.

    • Tuning the structural and catalytic properties of ceria by doping with Zr4+, La3+ and Eu3+ cations

      T Vinodkumar D Naga Durgasri Swamy Maloth Benjaram M Reddy

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      This work attempts to gain information about the role of trivalent and tetravalent dopants on the structural and catalytic properties of ceria (CeO2). In this study, we have prepared Zr4+, La3+, and Eu3+ doped ceria (CZ, CL, and CE) by coprecipitation method and calcined at 773 K. The physicochemical characterization was achieved by using various techniques, namely, X-ray powder diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area, high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), and electron spin resonance (ESR) spectroscopy. The catalytic efficiency for soot oxidation was evaluated by thermogravimetric (TG) method and compared with undoped CeO2. Doped CeO2 catalysts decreased the soot oxidation temperature by more than 158 K compared to pure ceria. This is ascribed to mutual interaction and synergistic effect between the dopant species and the ceria. Among the synthesized nanocatalysts, the CE sample exhibited better performance. The observed better activity of CE was attributed to the presence of more number of oxygen vacancies, a high specific surface area, and easy reducibility as confirmed from Raman, BET surface area, and TPR measurements, respectively.

    • Investigation of physicochemical properties and catalytic activity of nanostructured Ce0.7M0.3O2−𝛿 (M = Mn, Fe, Co) solid solutions for CO oxidation

      P Venkataswamy D Jampaiah C U Aniz Benjaram M Reddy

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      In this work, nanosized Ce0.7M0.3O2−𝛿 (M = Mn, Fe, Co) solid solutions were prepared by a facile coprecipitation method and evaluated for CO oxidation. The physicochemical properties of the synthesized samples were investigated by various characterization techniques, namely, XRD, ICP-OES, BET surface area, SEM-EDX, TEM and HRTEM, Raman, XPS, and H2 -TPR. XRD studies confirmed the formation of nanocrystalline single phase Ce0.7M0.3O2−𝛿 solid solutions. ICP-OES analysis confirmed actual amount of metal loadings in the respective catalysts. The BET surface area of Ce0.7M0.3O2−𝛿 samples significantly enhanced after the incorporation of dopants. TEM studies confirmed nanosized nature of the samples and the average particle sizes of Ce0.7M0.3O2−𝛿 were found to be in the range of ~8–16 nm. Raman studies indicated that the incorporation of dopant ions into the CeO2 lattice promote the formation of more oxygen vacancies. The existence of oxygen vacancies and different oxidation states (Ce3+/Ce4+ and Mn2+/Mn3+, Fe2+/ Fe3+, and Co2+/Co3+) in the doped CeO2 samples were further confirmed from XPS investigation. TPR measurements revealed an enhanced reducibility of ceria after the incorporation of dopants. The catalytic activity results indicated that the doped CeO2 samples show excellent CO oxidation activity and the order of activity was found to be Ce0.7Mn0.3O2−𝛿 > Ce0.7Fe0.3O2−𝛿 > Ce0.7Co0.3O2−𝛿 > CeO2. The superior CO oxidation performance of CeO2-MnOx has been attributed to a unique Ce-Mn synergistic interaction, which facilitates materials with promoted redox properties and improved oxidation activity.

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