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Hari Prasad Uppara,Sunit Kumar Singh,Nitin Kumar Labhsetwar,Mudiyaru Subrahmanya Murari,Harshini Dasari 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.7
The synthesis of binary mixed oxide Ce-Hf (CH), ternary mixed oxide Ce-Hf-Ru (CHR), and Ce-Hf-Mg (CHM) has been attempted using the PVP-assisted sol-gel method. The structural and surface morphology of the prepared catalysts were investigated and studied for the generation of superoxides (O2 )/peroxides (O2 2) species and availability of lattice oxygen (O) during soot oxidation reactions. The successfully incorporated Hf4+/Mg2+ into ceria (CH, CHM) enhances the redox potential sites on nano-flake morphology, thus produces more oxygen vacancies (□). However, Ru4+/Hf4+ was not doped into the ceria structure in CHR catalyst; it showed lesser structural distortions generating fewer oxygen vacancies. In addition, it was observed that better performing catalysts should possess lower oxidation temperature and be catalytically stable. Indeed, the ternary oxide CHR featured excellent catalytic properties when compared with the others. However, CHM was found structurally and catalytically stable with self-regenerative capability even after the repeated soot oxidation experiments. Thus, the possible soot oxidation mechanism has been proposed on the prepared catalysts.
이종호,Dasari Hari Prasad,손지원,Byung-Kook Kim,이해원 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.2
Using a glycine nitrate process (GNP), nanocrystalline GDC powder has been successfully prepared that can be sintered at 1200 oC to a relative density of 97% which is a significantly lower sintering temperature compared to that of conventional ceria-based electrolytes prepared by traditional solid state techniques. The effect of the glycine content on the particle size,morphology, and sintering behavior has been studied by changing the glycine-to-nitrate (G/N) ratio during the combustion synthesis. A range of techniques including thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR),X-ray diffraction (XRD), specific surface area determination (BET), particle size analysis (PSA) and scanning electron microscopy (SEM) were employed to characterize the GDC powders prepared. From the dilatometric studies, it is observed that the GDC powders prepared with a G/N ratio 0.55 show superior sintering activity compared to GDC powders prepared with a lower G/N ratio. A sintered GDC sample showed an ionic conductivity of 2.01 × 10−2 S/cm at 600 oC in air.
Effect of Ag loading on praseodymium doped ceria catalyst for soot oxidation activity
Pandurangappa Govardhan,Anjana Payyalore Anantharaman,Sunaina Shivasharanappa Patil,Hari Prasad Dasari,Harshini Dasari,Atmuri Shourya 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.2
Silver-loaded praseodymium doped ceria (XAg/PDC) was synthesized by microwave-assisted co-precipitation and wetness impregnation. XRD confirms the fluorite structure of ceria without secondary phase, and Raman spectroscopy represents the increased generation of oxygen vacancies with Ag loading. The TEM analysis shows lattice fringes corresponding to both CeO2 and Ag on the surface. The BET and BJH analysis of catalyst confirms the high porosity accompanied by high surface area and pore diameter of 5Ag/PDC and 15Ag/PDC, making it more active for the oxidation reaction. From the XPS analysis the amount of surface Ce3+ concentration and the surface chemisorbed oxygen species (O2 2) is high for 5Ag/PDC and 15Ag/PDC, in line with XRD and Raman results. The soot oxidation T50 temperature follows the trend: 5Ag/PDC~15Ag/PDC>10Ag/PDC>20Ag/PDC>0Ag/PDC. The Ag loading increased the surface reducibility of cerium ions and thus 5 wt% was optimized.
Praseodymium doped ceria as electrolyte material for IT-SOFC applications
Shajahan, Irfana,Ahn, Junsung,Nair, Parvathi,Medisetti, Srikar,Patil, Sunaina,Niveditha, V.,Uday Bhaskar Babu, G.,Dasari, Hari Prasad,Lee, Jong-Ho Elsevier 2018 Materials chemistry and physics Vol.216 No.-
<P><B>Abstract</B></P> <P>Praseodymium-doped ceria (PDC, Ce<SUB>0.9</SUB>Pr<SUB>0.1</SUB>O<SUB>2</SUB>) electrolyte material for intermediate temperature solid oxide fuel cells (IT-SOFCs) has been successfully synthesised by EDTA-citrate method. From X-Ray diffraction (XRD), fluorite structure along with a crystallite size of 5.4 nm is obtained for PDC nanopowder calcined at 350 °C/24 h. Raman spectroscopy confirmed the structure, presence of oxygen vacancies with the manifestation of the main peak at 457 cm<SUP>−1</SUP> and with a secondary peak at 550 cm<SUP>−1</SUP>. From Transmission Electron Microscopy (TEM) analysis, the average particle size is around 7–10 nm and selected area electron diffraction (SAED) patterns further confirmed the fluorite structure of PDC nanopowder. The PDC nanopowder displayed a BET surface area of 65 m<SUP>2</SUP>/g with a primary particle size of ∼13 nm (calculated from BET surface area). Dilatometer studies revealed a multi-step shrinkage behaviour with the multiple peaks at 522, 1171 and 1461 °C which may be originated due to the presence of multiple size hard agglomerates. The PDC electrolyte pellet sintered at 1500 °C displayed an ionic conductivity of 1.213E-03 S cm<SUP>−1</SUP> along with an activation energy of 1.28eV. Instead of a single fluorite structure, XRD of sintered PDC pellet showed multiple structures (Fluorite structure (CeO<SUB>2</SUB>) and cubic structure (PrO<SUB>2</SUB>).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Praseodymium doped ceria (PDC) electrolyte was synthesised by EDTA citrate method. </LI> <LI> Dilatometer study revealed multiple shrinkage behaviour of PDC. </LI> <LI> PDC showed an ionic conductivity of 1.213E-03 S cm<SUP>−1</SUP> at 700 °C. </LI> <LI> XRD at 1500 °C revealed that they crystallize as fluorite CeO<SUB>2</SUB> + cubic PrO<SUB>2</SUB> phase. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Oh, Eun‐,Ok,Whang, Chin‐,Myung,Lee, Yu‐,Ri,Park, Sun‐,Young,Prasad, Dasari Hari,Yoon, Kyung Joong,Son, Ji‐,Won,Lee, Jong‐,Ho,Lee, Hae‐,Weon WILEY‐VCH Verlag 2012 Advanced Materials Vol.24 No.25
<P><B>An extremely thin bilayer electrolyte</B> consisting of yttria‐stabilized zirconia (YSZ) and gadolinia‐doped ceria (GDC) is successfully fabricated on a sintered NiO‐YSZ substrate (see figure). Major processing flaws are effectively eliminated by applying local constraints to YSZ nanoparticles, and excellent open circuit voltage and cell performance are demonstrated in a solid oxide fuel cell (SOFC) at intermediate operating temperatures.</P>