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Item Open Access BaOx(Bilkent University, 2011) Emmez, EmreIn this work, formation anddecomposition pathways of of Ba(NO3)2 on BaOBaO2 /Pt(111) surfaces were investigated at the molecular levelfordifferent BaOBaO2coverages starting from small 2D islands of 0.5 MLE (MLE: monolayer equivalent) to thick multilayers of 10 MLE via temperature-programmed desorption (TPD), and X-ray Photoelectron Spectroscopy (XPS) and Low Energy Electron Diffraction (LEED). BaOxoverlayerswith a surface coverage of ~ 1 MLEreveallong range ordering with (2×2) and/or (1×2) structures while BaOx films with a surface coverage of1.5 MLEyields aBaO(110) termination and thicker films ( ≥ 5 MLE) were observed to be amorphous. Saturation of thick (10 MLE) BaOxoverlayers with NO2 leads to the formation of nitrates. Nitrate thermal decomposition was demonstrated to proceed through nitrite intermediates. In TPD experimentstwo major pathwaysfornitrate decomposition were observed: 1) nitrate decomposition yielding only NO evolutionat ~650 K, and 2) nitrate decomposition withNO + O2evolutionat ~700 K. This multi-step decomposition behavior was explained by BaO2 formation during the first stage. The influence of the BaOxdeposition method on the morphology of the BaOxoverlayers were established: when a thick BaOx layer is prepared using NO2 for Ba oxidation, BaOx overlayer efficiently wets the Pt(111) substrate forming a well-dispersed film. On the other hand, ifa thick BaOx layer is heated in O2 (to 873 K), BaOx overlayer agglomerates into 3D clusters, resulting in the formation of exposed (uncovered) Pt sites. BaOxoverlayers with uncoveredPt sitescan be “cured” by nitration – thermal decomposition procedures. When the BaOx layer coverage is below 2.5 MLE, nitrate decomposition temperature is observed at significantly lower temperatures, demonstrating the catalytic influence of the Pt sites facilitating the nitrate decomposition. It is proposed that initially, Ba(NO3)2 decomposesatthe boundary/peripheralsites of the Pt/BaOx interface, followed by the nitrate decomposition originating from 2D BaOx islands, and eventually from the 3D BaOx agglomerates. Catalytic deactivation of TiO2-promoted NOx-storage reduction (NSR) catalysts due to thermal aging effects was investigated using a BaO/TiO2/Pt(111) model catalyst system. At room temperature, metallic Ba overlayers on TiO2/Pt(111) was found to be very reactive towards oxide ions on TiO2/Pt(111) resulting in the formation of BaOx and partial reduction of TiO2. Ba films adsorbed on TiO2/Pt(111) that are further oxidized in O2 at 523 K lead to BaO and BaO2 surface domains which can efficiently adsorb both NO2 and CO2. Thermal treatment of BaOBaO2/TiO2/Pt(111) surface at T ≥ 300 K leads to a monotonic decrease in the surface Ba/Ti atomic ratio indicating the diffusion of BaO-BaO2 domains into the underlying TiO2 framework. Solid state reactions between BaOx and TiO2 particularly within 473-873K facilitate the formation of BaTiO3/Ba2TiO4/BaxTiyOz overlayers. After oxidation at higher temperatures (T > 873 K), surface becomes Badeficient and the enrichment of the surface with the Ti4+ sites results in a TiO2- terminated surface. Diffusion of BaOx into the TiO2 matrix and the enrichment of the surface with Ti sites drastically suppress the NO2 and CO2 adsorption/storage capacity of the model NOx storage system. These results reveal a direct evidence for the structural changes associated with the thermal deactivation of TiO2-promoted NSR catalysts.Item Open Access BaOx/ Pt(111) AND BaOx/ TiO2/ Pt(111) MODEL CATALYSTS FOR UNDERSTANDING NOx STORAGE-REDUCTION (NSR) CATALYSIS AT THE MOLECULAR LEVEL(Bilkent University, 2011) Emmez, EmreIn this work, formation anddecomposition pathways of of Ba(NO3)2 on BaOBaO2 /Pt(111) surfaces were investigated at the molecular levelfordifferent BaOBaO2coverages starting from small 2D islands of 0.5 MLE (MLE: monolayer equivalent) to thick multilayers of 10 MLE via temperature-programmed desorption (TPD), and X-ray Photoelectron Spectroscopy (XPS) and Low Energy Electron Diffraction (LEED). BaOxoverlayerswith a surface coverage of ~ 1 MLEreveallong range ordering with (2×2) and/or (1×2) structures while BaOx films with a surface coverage of1.5 MLEyields aBaO(110) termination and thicker films ( ≥ 5 MLE) were observed to be amorphous. Saturation of thick (10 MLE) BaOxoverlayers with NO2 leads to the formation of nitrates. Nitrate thermal decomposition was demonstrated to proceed through nitrite intermediates. In TPD experimentstwo major pathwaysfornitrate decomposition were observed: 1) nitrate decomposition yielding only NO evolutionat ~650 K, and 2) nitrate decomposition withNO + O2evolutionat ~700 K. This multi-step decomposition behavior was explained by BaO2 formation during the first stage. The influence of the BaOxdeposition method on the morphology of the BaOxoverlayers were established: when a thick BaOx layer is prepared using NO2 for Ba oxidation, BaOx overlayer efficiently wets the Pt(111) substrate forming a well-dispersed film. On the other hand, ifa thick BaOx layer is heated in O2 (to 873 K), BaOx overlayer agglomerates into 3D clusters, resulting in the formation of exposed (uncovered) Pt sites. BaOxoverlayers with uncoveredPt sitescan be “cured” by nitration – thermal decomposition procedures. When the BaOx layer coverage is below 2.5 MLE, nitrate decomposition temperature is observed at significantly lower temperatures, demonstrating the catalytic influence of the Pt sites facilitating the nitrate decomposition. It is proposed that initially, Ba(NO3)2 decomposesatthe boundary/peripheralsites of the Pt/BaOx interface, followed by the nitrate decomposition originating from 2D BaOx islands, and eventually from the 3D BaOx agglomerates. Catalytic deactivation of TiO2-promoted NOx-storage reduction (NSR) catalysts due to thermal aging effects was investigated using a BaO/TiO2/Pt(111) model catalyst system. At room temperature, metallic Ba overlayers on TiO2/Pt(111) was found to be very reactive towards oxide ions on TiO2/Pt(111) resulting in the formation of BaOx and partial reduction of TiO2. Ba films adsorbed on TiO2/Pt(111) that are further oxidized in O2 at 523 K lead to BaO and BaO2 surface domains which can efficiently adsorb both NO2 and CO2. Thermal treatment of BaOBaO2/TiO2/Pt(111) surface at T ≥ 300 K leads to a monotonic decrease in the surface Ba/Ti atomic ratio indicating the diffusion of BaO-BaO2 domains into the underlying TiO2 framework. Solid state reactions between BaOx and TiO2 particularly within 473-873K facilitate the formation of BaTiO3/Ba2TiO4/BaxTiyOz overlayers. After oxidation at higher temperatures (T > 873 K), surface becomes Badeficient and the enrichment of the surface with the Ti4+ sites results in a TiO2- terminated surface. Diffusion of BaOx into the TiO2 matrix and the enrichment of the surface with Ti sites drastically suppress the NO2 and CO2 adsorption/storage capacity of the model NOx storage system. These results reveal a direct evidence for the structural changes associated with the thermal deactivation of TiO2-promoted NSR catalysts.Item Open Access Ceria promoted NOx storage and reduction materials(Bilkent University, 2011) Say, ZaferIn the current work, the effect of CeO2 promotion on the NOx storage materials and NOx storage-reduction (NSR) catalysts is studied. Synthesized materials were prepared using different baria and ceria loadings in order to investigate the influence of the surface composition on the NOx storage process. Synthesized materials were also thermally treated in the temperature range within 300 - 1273 K to mimic the thermal aging effects on the material structure. Structural properties of the synthesized materials were investigated via spectroscopic and diffraction techniques such as Raman spectroscopy, X-ray diffraction (XRD), and BET (Brunauer, Emmett, ve Teller) surface area analysis. These ex-situ characterization studies revealed that materials containing Pt showed indications of sintering after thermal treatment at elevated temperatures where Pt sites grew in size and were partially covered by BaO domains. Pt addition to the BaO/Al2O3 system facilitated the formation of the undesired BaAl2O4 phase, particularly at high baria loadings. Decomposition of the Ba(NO3)2 species took place at lower temperatures for Pt containing materials. An indication for a strong-metal-support interaction (SMSI) between Pt and CeO2 sites was observed in Raman spectroscopic data, resulting in the formation of a new mixed oxide phase on the surface. BET results indicated that the specific surface area (SSA) of the synthesized materials monotonically decreased with increasing temperature and increasing BaO and CeO2 loadings. The behavior of the synthesized materials in NOx and SOx adsorption experiments were also investigated via temperature programmed desorption (TPD) and in-situ Fourier transform infrared (FTIR) spectroscopy. Ceria promotion had no significant influence on the nature of the adsorbed nitrate species and the NOx uptake ability of the alumina support material. On the other hand, addition of Pt to CeO2/Al2O3 binary and BaO/CeO2/Al2O3 ternary systems was observed to enhance the NOx storage. For the ternary mixed oxide NOx storage systems (BaO/CeO2/Al2O3), increasing BaO or CeO2 loadings results in a decrease in the specific surface area values, which in turn leads to decreasing NOx uptake. SO2 (g) + O2 (g) interaction with a selected set of samples were also investigated via in-situ FTIR spectroscopy. These experiments reveal that ceria promotion and platinum addition assisted the formation of surface sulfate species. Furthermore, the presence of ceria also resulted in a decrease in the thermal stability of sulfates and enabled easier regeneration.Item Open Access Enhanced sulfur tolerance of ceria-promoted NOx storage reduction (NSR) catalysts: sulfur uptake, thermal regeneration and reduction with H2(g)(Springer New York LLC, 2013) Say, Z.; Vovk, E. I.; Bukhtiyarov, V. I.; Ozensoy, E.SOx uptake, thermal regeneration and the reduction of SOx via H2(g) over ceria-promoted NSR catalysts were investigated. Sulfur poisoning and desulfation pathways of the complex BaO/Pt/CeO2/Al2O3 NSR system was investigated using a systematic approach where the functional sub-components such as Al2O3, CeO2/Al2O3, BaO/Al2O3, BaO/CeO2/Al2O3, and BaO/Pt/Al2O3 were studied in a comparative fashion. Incorporation of ceria significantly increases the S-uptake of Al2O3 and BaO/ Al2O3 under both moderate and extreme S-poisoning conditions. Under moderate S-poisoning conditions, Pt sites seem to be the critical species for SOx oxidation and SOx storage, where BaO/Pt/Al2O3 and BaO/Pt/CeO2/Al2O3 catalysts reveal a comparable extent of sulfation. After extreme S-poisoning due to the deactivation of most of the Pt sites, ceria domains are the main SOx storage sites on the BaO/Pt/CeO2/Al2O3 surface. Thus, under these conditions, BaO/Pt/CeO2/Al2O3 surface stores more sulfur than that of BaO/Pt/Al2O3. BaO/Pt/CeO2/Al2O3 reveals a significantly improved thermal regeneration behavior in vacuum with respect to the conventional BaO/Pt/Al2O3 catalyst. Ceria promotion remarkably enhances the SOx reduction with H2(g).Item Open Access Finding an optimum surface chemistry for [Formula] systems as NOx storage materials(Bilkent University, 2010) Şentürk, Göksu SedaTitania promoted NOx storage materials in the form of BaO/TiO2/Al2O3 were synthesized via two different sol-gel preparation techniques, with varying surface compositions and morphologies [1, 2]. The influence of the TiO2 units on the NOx storage component (8 - 20 wt. % BaO), the nature of the crystallographic phases, thermal stabilities and the dispersion of the surface oxide/nitrate domains were investigated. The structural characterization of the synthesized NOx storage materials were analyzed by means of BET surface area analysis, X-ray diffraction (XRD), ex-situ Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X- ray (EDX) and transmission electron microscopy (TEM). Comparative analysis of the results showed that the TiO2/Al2O3 support material derived by the co-precipitation of the corresponding hydroxides via the sol-gel technique, exhibited distinctively more homogenous distribution of TiO2 domains. The functionality/performance of these materials upon NOx and SOx adsorptions were monitored by temperature programmed desorption (TPD) and insitu Fourier transform infrared (FTIR) spectroscopy. An improved Ba surface dispersion was observed for the BaO/TiO2/Al2O3 materials synthesized via the coprecipitation of alkoxide precursors which was found to originate mostly from the increased fraction of accessible TiO2/TiOx sites on the surface. These TiO2/TiOx sites functioned as strong anchoring sites for surface BaO domains and were tailored to enhance surface dispersion of BaO. The relative stability of the NOx species adsorbed on the BaO/TiO2/Al2O3 system was found to increase in the following order: NO+ /N2O3 on alumina << nitrates on alumina < surface nitrates on BaO < bridged/bidentate nitrates on large/isolated TiO2 clusters < bulk nitrates on BaO on alumina surface and bridged/bidentate nitrates on TiO2 crystallites homogenously distributed on the surface < bulk nitrates on the BaO sites located on the TiO2 domains. The detailed study of the interaction of SOx with BaO/TiO2/Al2O3 ternary oxide materials showed that titania (TiO2) was a promising candidate for improving the sulfur tolerance on these type of surfaces. Adsorption of SOx on both pure Al2O3 and TiO2 showed that Al2O3 formed strongly bound SOx species, that were thermally stable up to T > 1073 K. SOx adsorption directly altered stability of the nitrate species on the Ti/Al (Protocol 1, Protocol 2) samples. SOx uptake properties of the BaO/TiO2/Al2O3 materials were found to be strongly influenced by the morphology of the TiO2/TiOx domains and the BaO loadings (8/20 wt% BaO). Consequently, the presence of titania domains was seen to decrease the SOx desorption temperatures and enhance the sulfur-tolerance of these materials by destabilizing the accumulated sulfate species. SOx exposure on the synthesized materials led to a significant decrease in the NOx adsorption capacities. The results obtained from FT-IR spectra showed that the sulfur deposition on the NOx storage materials promoted by TiItem Open Access NOx storage and reduction pathways on zirconia and titania functionalized binary and ternary oxides as NOx storage and reduction (NSR) systems(Elsevier, 2014-08-01) Say, Z.; Tohumeken, M.; Ozensoy, E.Binary and ternary oxide materials, ZrO2/TiO2 (ZT) and Al2O3/ZrO2/TiO2 (AZT), as well as their Ptfunctionalized counterparts were synthesized and characterized via XRD, Raman spectroscopy, BET, in situ FTIR and TPD techniques. In the ZT system, a strong interaction between TiO2 and ZrO2 domains at high temperatures (>973K) resulted in the formation of a low specific surface area (i.e. 26 m2/g at 973K) ZT material containing a highly ordered crystalline ZrTiO4 phase. Incorporation of Al2O3 in the AZT structure renders the material highly resilient toward crystallization and ordering. Alumina acts as a diffusion barrier in the AZT structure, preventing the formation of ZrTiO4 and leading to a high specific surface area (i.e. 264 m2/g at 973K). NOx adsorption on the AZT system was found to be significantly greater than that of ZT, due to almost ten-fold greater SSA of the former surface. While Pt incorporation did not alter the type of the adsorbed nitrate species, it significantly boosted the NOx adsorption on both Pt/ZT and Pt/AZT systems. Thermal stability of nitrates was higher on the AZT compared to ZT, most likely due to the defective structure and the presence of coordinatively unsaturated sites on the former surface. Pt sites also facilitate the decomposition of nitrates in the absence of an external reducing agent by shifting the decomposition temperatures to lower values. Presence of Pt also enhances partial/complete NOx reduction in the absence of an external reducing agent and the formation of N2 and N2O. In the presence of H2(g), reduction of surface nitrates was completed at 623K on ZT, while this was achieved at 723K for AZT. Nitrate reduction over Pt/ZT and Pt/AZT via H2(g) under mild conditions initially leads to conversion of bridging nitrates into monodentate nitrates/nitrites and the formation of surface OH and NHx functionalities. N2O(g) was also continuously generated during the reduction process as an intermediate/byproduct.Item Open Access SOx uptake and release properties of TiO2/Al2O3 and BaO/TiO2/Al2O3 mixed oxide systems as NOx storage materials(Elsevier, 2012-04-30) Şentürk, G. S.; Vovk, E. I.; Zaikovskii, V. I.; Say, Z.; Soylu, A. M.; Bukhtiyarov, V. I.; Ozensoy, E.Titania was used as a promoter to obtain novel materials in the form of TiO2/Al2O3 (Ti/Al) and BaO/TiO2/Al2O3 (Ba/Ti/Al, containing 8 wt% or 20 wt% BaO) that are relevant to NOx storage reduction (NSR) catalysis. Two different protocols (P1, P2) were utilized in the synthesis. Ti/Al(P1) manifests itself as crystallites of TiO2 on -Al2O3, while Ti/Al(P2) reveals an amorphous AlxTiyOz mixed oxide. The structures of the synthesized materials were investigated via TEM, EDX, BET analysis and XPS while the catalytic functionality/performance of these support materials upon SOx and subsequent NOx adsorption were investigated with TPD and in situ FTIR spectroscopy. Ti/Al(P1, P2) revealed a high affinity towards SOx. Overall thermal stabilities of the adsorbed SOx species and the total SOx uptake of the Ba-free samples increase in the following order: TiO2(anatase) -Al2O3 < Ti/Al(P1) < Ti/Al(P2). The superior SOx uptake of Ti/Al(P1, P2) support materials can be tentatively attributed to the increasing specific surface area upon TiO2 promotion and/or the changes in the surface acidity. Promotion of BaO/Al2O3 with TiO2 leads to the attenuation of the SOx uptake and a significant decrease in the thermal stability of the adsorbed SOx species. The relative SOx adsorption capacities of the investigated materials can be ranked as follows: 8Ba/Ti/Al(P1) < 8Ba/Ti/Al(P2) < 8Ba/Al ∼ 20Ba/Ti/Al(P1) < 20Ba/Al < 20Ba/Ti/Al(P2).Item Open Access Structure and NOx uptakr properties of Fe-Ba/Al2O3 as a model NOx storage material(Bilkent University, 2009) Kayhan, EmineThe composition-effect of iron (5 and 10 wt. % Fe) on the nature of the NOx species and NOx storage properties of (8 and 20 wt. %) BaO/γ-Al2O3 was investigated. Nitrate-loaded samples, which were synthesized by incipient-wetness impregnation with nitrate precursors, were further treated at elevated temperatures (323 K-1273 K) in order to monitor the thermally induced structural changes. In the first part of this study, diffraction (X-ray Diffraction, XRD), BET (Brunauer, Emmett, and Teller) surface area measurement, spectroscopy (Raman and X-Ray Photoelectron Spectroscopy, XPS) and microscopy (Transmission Electron Microscopy, TEM and Electron Energy Loss Spectroscopy, EELS) techniques were used for investigating the thermally induced structural changes on the sample surfaces. In the second part of the text, NO2 (g) adsorption experiments were performed on the NOx-free samples. FTIR (Fourier Transform Infrared) spectroscopy technique was used to monitor the NOx species stored on the samples. To illustrate the desorption behavior of the adsorbed NOx on 8Ba/Al sample, Temperature Programmed Desorption (TPD) technique was also exploited. For the as prepared (nitrated) samples, the surface distribution and the thermal stability of the deposited Ba-nitrates were found to depend strongly on the interaction with the Fe-containing domains and the γ-Al2O3 support material. It was observed that deposited nitrates have a different thermal stability on the Fe/Ba/Al samples in comparison to the Fe-free Ba/Al samples. Besides, XRD data revealed that BaAl2O4 formation at elevated temperatures was diminished to a certain extent in the presence of Fe. Moreover, the presence of Fe in the form of α- Fe2O3 in the Fe/Al and BaFe/Al systems depressed the γ-Al2O3 → α-Al2O3 phase transformation temperature and favored the corundum formation above 1073 K. Relative surface dispersions of the Fe- and Ba-species on the 10Fe/20Ba/Al sample were also analyzed via TEM and EELS where the dispersion of barium species were found to be relatively higher than that of iron. FTIR experiments revealed that NO2 (g) adsorption at 323 K leads to the formation of nitrites for all of the samples at the initial introduction of NO2 (g). In addition, iron containing samples indicate nitrosyl formation as well. With further doses of NO2 (g), nitrite bands were converted into nitrate signals. NO2 (g) adsorption on 5(10)Fe/8(20)Ba/Al system resulted in the accentuation of the surface/bidentate nitrates. Temperature dependent FTIR experiments showed that ionic (bulk) nitrates were thermally more stable than the surface nitrates in 8(20)Ba/Al and 5(10)Fe/8(20)Ba/Al systems. TPD profile for the 8Ba/Al sample was also found to be in line with the FTIR results, indicating that the high-temperature decomposition of bulk nitrates were in the form of NO (g) and O2 (g) while the surface nitrates decomposed at lower temperatures and mostly as NO2 (g). In the presence of Fe (5 and 10 wt %) thermal stability of the nitrates were found to decrease.Item Open Access Sulfur tolerance of Fe promoted BaO/Al2O3 systems as NOx storage materials(Bilkent University, 2011) Parmak, EmrahTernary mixed oxide systems in the form of BaO/FeOx/Al2O3 were studied with varying compositions as an alternative to the conventional NOx storage materials (i.e. BaO/Al2O3). NOx uptake properties of the freshly prepared samples, sulfur adsorption and NOx storage in the presence of sulfur were investigated in order to elucidate the sulfur tolerance of these advanced NOx storage systems in comparison to their conventional counterparts. The structural characterization of the poisoned NOx storage materials was analyzed by means of scanning electron microscopy (SEM). The performance and sulfur tolerance of these materials upon SOx adsorption were monitored by in-situ Fourier transform infrared (FTIR) spectroscopy, temperature programmed desorption (TPD) and X-Ray Photoelectron Spectroscopy (XPS). Addition of FeOx domains to the conventional BaO/Al2O3 system was observed to introduce additional NOx storage sites and tends to increase the total NOx uptake capacity. SO2+O2 adsorption on the investigated samples was found to lead to the formation of sulfites at low temperatures which are converted into surface and bulk sulfates with increasing temperatures. After annealing at 1173 K in vacuum most of the sulfates can be removed from the surface and the samples can be regenerated. However, for Fe/Ba/Al samples formation of various highly-stable sulfite and sulfate species were also observed which survive on the surface even after annealing at elevated temperatures (1173 K). Sulfur poisoning on 5(10)Fe/8Ba/Al samples leads to preferential poisoning of the FeOx, Al2O3 and surface BaO sites where bulk BaO sites seems to be more tolerant towards sulfur poisoning. In contrast, sulfur poisoning occurs in a rather non-preferential manner on the 5(10)Fe/20Ba/Al samples influencing all of the NOx storage sites. Thermal stability of the sulfate species seem to increase in the following order: surface alumina sulfates < surface Ba sulfates ≈ Fe sulfates < bulk Ba sulfates ≈ bulk alumina sulfates < highly stable sulfates and sulfites on Fe/Ba/Al surfaces. In overall, it can be argued that the Fe promotion has a positive influence on the NOx storage capacity as well as a positive effect on the sulfur tolerance when the Ba loading is equal to 8 wt% (i.e. 5(10)Fe/8Ba/Al). For these samples, even the surface uptakes more SOx than conventional 8Ba/Al system, NOx uptake properties as well as thermal regeneration properties seem slightly improved. On the other hand, for higher Ba loadings (i.e. 5(10)Fe/20Ba/Al) Fe promotion has a minor positive effect on NOx uptake capacity and SOx tolerance for 5 wt% Fe promotion while 10 wt% Fe promotion seems to have no positive influence.Item Open Access Utilization of reducible mixed metal oxides as promoters for the enhancement of sulfur regeneration in nsr catalysts(Bilkent University, 2016-07) Samast, Zehra AybegümPt functionalized binary, ternary, and quaternary oxides (e.g. Pt/BaO/CeO2/ZrO2/Al2O3) were synthesized by wetness impregnation method and characterized by X-ray Diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, in-situ Fourier Transform Infrared (FTIR), and temperature programmed desorption (TPD) techniques. Effect of the synthesis sequence on the NOx storage capacity was investigated by synthesizing subsequently impregnated and co-impregnated ternary oxides. Influence of BaO loading on NOx uptake of quaternary oxides was examined by utilizing two different BaO loadings namely; 8 wt% and 20 wt% on co-impregnated ternary oxide, Pt10-10CeZrAl. Co-presence of CeO2-ZrO2 oxide domains leads to an increase in NOx storage. As BaO loading increases in quaternary oxides, thermal stabilities of nitrates and nitrites increase due to the formation of bulk/ionic nitrates. Although BaO impregnation on co-impregnated ternary oxides leads to a decrease in specific surface area (SSA) values due to sintering, NOx adsorption on BaO-functionalized quaternary oxides was found to be higher than the BaO deficient ternary oxides. Upon sulfur poisoning, formation of strongly bound bulk/ionic sulfate/sulfite functional groups on BaO containing catalysts result in a need for higher temperatures for complete sulfur regeneration. Comparison of the CeO2-ZrO2 promoted systems with that of the Pt/ 20 wt% Ba/Al2O3 conventional NOx Storage Reduction (NSR) catalyst suggests that ceria-zirconia promotion enhances the sulfur tolerance. In conclusion, in this study a new NSR catalyst namely, Pt20Ba10-10CeZrAl, which is promoted with reducible mixed metal oxides, was synthesized and characterized. This novel NSR catalyst formulation revealed favorable sulfur resistance with minor sacrifice in NOx storage ability.