Catalyst CeO2 Research Articles

Boosting H2O2 activation by Cu and Ce co-doped g-C3N4 for pollutants removal: From the free radical pathway to the non-free radical pathway

Recently, materials synthesized by combining graphitic carbon nitride (g-C3N4) and metallic material have caught a lot of attention because of their high catalytic activity. In this paper, a novel g-C3N4 catalyst doped with Cu and Ce (labeled as CuCe-CN) is presented. CuCe-CN can effectively activate H2O2 to degrade tetracycline hydrochloride (TC-HCl) and cause TC-HCl to be completely degraded within one hour. The presence of CeO2 in catalyst provides the redox electron pairs of Ce(IV) and Ce(Ⅲ), and also facilitates the generation of 1O2 during the experimental process. By comparing the main active substances of CuCe-CN and Cu-CN, the fact that the doping of Ce changes the degradation pathway from free radical pathway to non-free radical pathway can be found. It can be demonstrated by electrochemical tests that the doping of Ce promotes the electron transfer in CuCe-CN, which can benefit the generation of reactive oxidation species (ROS), especially 1O2. CuCe-CN/H2O2 system has a good adaptability to the changes of environment. The catalytic performance of CuCe-CN does not be negatively affected by inorganic salt ions, and maintains high activity in natural aqueous environments. In this research, a new method for optimizing the activation behavior of g-C3N4 and a new non-free radical degradation method of TC-HCl were provided.

Study on the differences between non-catalytic and catalytic oxidation of soot based on catalyst CeO2

Exploring the differences between soot non-catalytic and catalytic oxidation process is beneficial to enhance the catalyst performance and soot removal efficiency of catalytic diesel particulate filters. In this paper, the soot samples are pretreated under high temperature conditions at both non-catalytic and catalytic oxidation atmosphere to obtain target pretreated soot samples with different mass loss. Five typical oxidation stages are analyzed with corresponding soot mass loss rate of 15 %, 25 %, 50 %, 70 %, 85 %. The soot physicochemical properties including oxidation activity, porous structure, particle layer, nanostructure, graphitization and functional groups are explored; further, the correlations among these physicochemical properties are analyzed, and three levels of catalytic effect mechanism are proposed based on CeO2 catalyst. This paper helps in understanding the differences of the mechanisms between non-catalytic and catalytic oxidation of soot.

Improvement of NOx and CO Reduction Performance at Low Temperature of H2-SCR Catalyst

The purpose of this study is to improve the simultaneous reduction of NOX and CO, harmful gases emitted from internal combustion engines, at low temperatures using a Pt/TiO2 H2-SCR catalyst. A better NOX/CO reduction performance was observed upon loading 2 wt% of the additive catalyst CeO2 on the main catalyst Pt because the oxygen storage capacity improved. In the presence of CO, the water gas reaction was promoted, resulting in the NOX conversion rate by the 0.5Pt−2CeO2/TiO2 SCR catalyst of 42 % at 75 °C and 70 % at 100 °C; this was a 15 ∼ 20 % higher NOX conversion as compared to without CO at low temperatures. The NOX reduction performance by the 0.5Pt−2CeO2−2ZrO2/TiO2 SCR catalyst was the highest at temperatures below 100 °C. At an appropriate amount of the additive catalyst ZrO2, the reaction rate improved because the acid point of the catalyst surface and the intensity of adsorption are adjusted. The optimum reduction temperature for NOX/CO reduction performance by the H2-SCR catalyst was 400 °C. Our results also indicate that the Pt species has a significant impact.

Catalytic Dye Oxidation over CeO2 Nanoparticles Supported on Regenerated Cellulose Membrane

A novel regenerated cellulose (RC) membrane containing cerium oxide (CeO2) nanoparticles is described in detail. In this work, CeO2 nanoparticles with high surface area and mesoporosity were prepared by a modified template-assisted precipitation method. Successful synthesis was achieved using cerium nitrate as a precursor, adjusting the final pH solution to around 11 by ammonium hydroxide and ethylene diamine, and annealing at 550 °C for 3 hours under a protective gas flow. This resulted in a surface area of 55.55 m².g–1 for the nanoparticles. The regenerated cellulose membrane containing CeO2 particles was synthesized by the novel and environmentally friendly method. The catalyst CeO2 and cellulose/CeO2 membrane were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Electron paramagnetic resonance (EPR), and Brunauer-Emmett-Teller (BET) measurements. The g-value of 2.276 has confirmed the presence of the surface superoxide species of CeO2 nanoparticles in EPR. The photocatalytic activity of the catalyst and the membrane containing the catalyst was evaluated through the degradation of methylene blue under visible light irradiation by UV-VIS measurements. The cellulose/CeO2 membrane degraded 80% of the methylene blue solution in 120 minutes, showing a better photocatalytic activity than the CeO2 catalyst, which degraded approximately 62% in the same period. It has been proven that the RC membrane is not only a good transparent supporting material but also a good adsorption for high-performance of CeO2 catalyst. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Degradation of persistent organic pollutants in soil by parallel tubes-array dielectric barrier discharge plasma cooperating with catalyst

Persistent organic pollutants are harmful to the human health and environment due to their toxicity, chemical stability, degradation resistance and high bioaccumulation. In this paper, a parallel tubes-array dielectric barrier discharge reactor is developed to generate homogeneous discharge plasma and degrade the persistent organic pollutants in soil. The effects of applied voltage, initial concentration of pyrene and catalysts on the pyrene degradation efficiency in soil are studied. The results show that the degradation effect can be greatly improved by tuning these influencing parameters. The degradation efficiency of pyrene is significantly enhanced as the applied voltage increases. It reaches 96.23% at 28 kV in simulated soil and 98.26% at 26 kV in actual soil with 100 mg/kg initial concentration, and 10 min plasma treatment time. A significant promotion effect on the degradation efficiency can be obtained with the decrease of the initial pyrene concentration. Likewise, the addition of the catalysts CeO2 and TiO2 significantly improves the pyrene degradation efficiency and presents obvious synergistic effect with plasma. The discharge characteristics are discussed in combination with discharge images, waveforms of current and voltage. And the degradation mechanism of pyrene is analyzed combine with the optical emission spectra.

Enriched oxygen vacancy promoted heteroatoms (B, P, N, and S) doped CeO2: Challenging electrocatalysts for oxygen evolution reaction (OER) in alkaline medium

Increasing worldwide energy consumption has prompted considerable study into energy generation and energy storage systems in recent years. Chemical fuels may be produced efficiently via electrocatalytic water splitting, which uses electric and solar power. The development of efficient anodic electrocatalysts for efficient oxygen evolution reaction (OER) is a greater concern of present energy research. Cerium oxide (CeO2) are promising electrocatalysts that exhibit outstanding OER but their reduced stability obstructs the practical application. A novel strategy was established to construct an effective catalyst of heteroatom (N, B, P and S) doped CeO2 matrix were prepared. Moreover, the doping of heteroatoms into the CeO2 matrix processes the improved electronic conductivity, reactive sites, increases the electrochemical catalytic activity, which enhances the water oxidation reaction. Consequently, well-suited alkaline electrolysers were brought together for water oxidation to ideal OER electrocatalytic activity. The OER activity of the electrocatalysts follows the order of S–CeO2 (190 mV@10 mA cm−2), N– CeO2 (220 mV @10 mA cm−2), P– CeO2 (230 mV @10 mA cm−2), B–CeO2 (250 mV @10 mA cm−2) and CeO2 (260 mV @10 mA cm−2) in 1 M of KOH. From the kinetics analysis, Tafel slope value achieved for catalysts CeO2, B–CeO2, P–CeO2, N–CeO2 and S–CeO2 are 142 mV dec−1,121 mV dec−1, 102 mV dec−1, 98 mV dec−1 and 83 mV dec−1 respectively. These results validate that the S–CeO2 electrode is prominent for OER performance with the requirement of cell voltage of 1.42 V at 10 mA cm−2 current density. In addition, sulphur doped CeO2 relatively have excellent stability through chrono-potentiometric analysis lasting for 20 h. Although the heteroatoms doped CeO2 is acts as anode material, the preparation method is widespread, which will reduce the synthesis cost and streamline the preparation of electrode for OER. This research effort delivers a complete advantage for the development of robust, environmentally friendly and highly dynamic electrocatalysts for OER activity.

Influence of CeO2 nanoparticles on microstructure and hydrogen storage performance of Mg-Ni-Zn alloy

The Mg85Ni10Zn5 + x wt% CeO2 (x = 0, 2, 4, 8) composites were synthesized by high energy ball milling. The phase structures of as-milled composites were characterized, and the results showed that the hydrogen storage reaction mechanism can be concluded as: Mg + H2 ↔ MgH2, Mg2Ni + H2 ↔ Mg2NiH4, and MgZn2 phase and the catalyst CeO2 nanoparticles do not react during the hydrogenation/dehydrogenation process. The composites can absorb/desorb ~5.28 wt% hydrogen reversibly in about 10 min above 320 °C. Moreover, the hydriding/dehydriding reaction rate of CeO2 catalyzed composites is much faster than un-catalyzed one. The activation energy of dehydrogenation was decreased from 109.83 to 82.93 kJ/mol H2 by adding 4 wt% CeO2. It indicates that the hydrogen storage kinetics of the composites was expedited by the adding of catalyst CeO2 nanoparticles, which is attributing to more phase interfaces and grain boundaries were provided by milling Mg85Ni10Zn5 with CeO2 nanoparticles and it means more hydrogen atom diffusion channels and reaction nucleation positions were offered for hydrogenation/dehydrogenation reaction. However, the hydrogen storage thermodynamic properties of Mg85Ni10Zn5 alloy have enhanced slightly by milling Mg85Ni10Zn5 with CeO2 nanoparticles.

Study on the effect of Ce1-xMnxO2 catalyst on improving diesel emission performance

To reduce diesel emissions while permitting the passive regeneration of the diesel particulate filter (DPF) at low temperatures, we developed three after-treatment DPF devices. These devices consisted of a ceramic body that was either bare or loaded with the catalysts CeO2 (DPF-CeO2) or Ce0.5Mn0.5O2 (DPF-Ce0.5Mn0.5O2). The effects of these units on soot, NOx, CO, and hydrocarbon emissions were assessed. On average, the DPF-Ce0.5Mn0.5O2 device outperformed the DPF-CeO2 device. In addition, increasing the engine load was found to raise the exhaust temperature while increasing the soot oxidation efficiency and reducing soot emissions. The maximum soot removal percentages of the DPF-CeO2 and DPF-Ce0.5Mn0.5O2 were 37.6% and 55.1%, respectively, under B100 working conditions. The extent of NOx removal also gradually increased as the load increased, and the average removal percentages were 8.6% and 15.0%, respectively. Both catalytic devices lowered CO emissions to a much greater extent than the bare DPF, with average removals of 45.8% and 55.6%, respectively, while the average hydrocarbon oxidation values were 39.1% and 50.9%, respectively. Notably, the hydrocarbon emissions were almost zero after Ce1-xMnxO2 catalysis under C100 working conditions.

High activity of CeO2-TiO2 composites for deep oxidation of 1,2-dichloroethane

CeO2-TiO2 catalysts prepared by different methods were investigated for deep oxidation of 1,2-dichloroethane (DCE), as a typical representative of the chlorinated volatile organic compounds (CVOCs). Characterization analysis reveals that CeO2-TiO2 catalysts prepared by sol-gel and coprecipitation methods exhibit higher specific area, CeO2 and TiO2 particles are highly dispersed into each other and the reducibility and mobility of active oxygen species are obviously promoted due to the strong interaction between the two catalysts CeO2 and TiO2, resulting in higher catalytic activity for DCE oxidation to and less chlorinated byproduct. The high calcination temperature would lead to the formation of a new monoclinic phase Ce0.3Ti0.7O2 and sintering, which is the main reason for the catalytic activity for DCE oxidation markedly decreases.

Preparation of CeO2 nanorods-reduced graphene oxide hybrid nanostructure with highly enhanced decolorization performance

Decolorization by both adsorption and catalysis method, especially for the synergistic effect of these two methods is very important. Here, we report that CeO2 nanorods (NRs) with different amounts (wt%) of reduced graphene oxide (RGO) have been prepared by a facile hydrothermal method. The decolorization tests show that decolorization of methyl blue (MB) is attributed to both catalysis and absorption, though its adsorption over the catalyst CeO2 NRs-RGO mainly influences the decolorization, the visible light irradiation plays a vital role in increasing the decolorization efficiency. Incorporating RGO into CeO2 NRs matrix not only changes surface morphology and area, particle size, band gap, crystal structure and oxygen vacancy content of the latter, but also causes mutual charge transfer between RGO and CeO2 NRs, which therefore increases the decolorization efficiency of CeO2 NRs-RGO to be 95.4% and to be as high as 99.5% after addition of electron scavenger H2O2. The study demonstrates the synergistic effect of adsorption and photo-catalysis are very important in MB decolorization process over CeO2 NRs-RGO (9.2 wt%) and provides a possible way in the design of decolorization agent.

CuO/CeO2–MnO2 Catalyst Prepared by Redox Method for Preferential Oxidation of CO in H2-Rich Gases

CuO/CeO2–MnO2 (CuCeMn-4) catalyst was prepared by redox method and was tested in the CO preferential oxidation in H2-rich gases (CO PROX). CuO/CeO2–Mn2O3 (CuCeMn-3) catalyst was prepared and tested for comparison. CuCeMn-4 exhibits higher catalytic activity than CuCeMn-3. The complete CO conversion with CO2 selectivity of 92% can be obtained at 120 °C over CuCeMn-4. The catalysts were characterized by means of N2 adsorption/desorption, XRD, H2-TPR and XPS techniques. The results show that the interaction between MnO2 and CeO2 in catalyst is stronger than Mn2O3 and CeO2, which can promote the mobility of oxygen species from CeO2–MnO2 to active copper species. XPS characterization further revealed that CuCeMn-4 contains richer lattice oxygen, higher amount of Cu+ species and less carbonate species on the surface as compared with CuCeMn-3. All these should be greatly responsible for the high activity of CuCeMn-4 catalyst.

Exploration of reaction mechanism between acid gases and elemental mercury on the CeO2–WO3/TiO2 catalyst via in situ DRIFTS

Although the oxidation of elemental mercury (Hg0) on catalyst can be significantly affected by acid gases, its mechanism is still unclear. This study used in situ DRIFT to research the influence of acid gases (NO, HCl and SO2) on the performance of mercury oxidation on catalyst CeO2(5)–WO3(9)/TiO2. The catalyst could capture a large amount of Hg0 on the surface yet not oxidize all Hg0 into gaseous oxidation mercury (Hg2+) due to the limit of oxidation sites (CeO2). The addition of NO and HCl improved the mercury oxidation efficiency because this process transformed the adsorbed mercury on the catalyst into gaseous Hg2+ and formed new active sites. The in situ DRIFTS result indicated that NO2 and nitrate served as active sites for mercury oxidation. The formation of active chlorine (Cl∗) via HCl adsorption on the catalyst promoted the transformation of mercury into gaseous HgCl2. The NO and HCl addition could keep the mercury oxidation efficiency over 91.5% with the presence of 500–3000 ppm SO2 and increase the SO2 resistance of the catalyst. The reaction of NO and Hg0 conforms to the Eley-Ridcal mechanism, while the reaction of HCl and Hg0 follows the Languir-Hinshelwood mechanism.

Combination of catalytic combustion and catalytic denitration on semi-coke with Fe2O3 and CeO2

The processes of catalytic combustion and catalytic denitration of semi-coke were conducted in the presence of catalysts Fe2O3 and CeO2, The comprehensive performance of these processes was evaluated with thermogravimetry analysis and infrared spectroscopy. The results indicate that the combustion activity improved significantly when we added Fe2O3 and CeO2 separately. Furthermore, the mixture of Fe2O3 and CeO2 has better combustion efficienty. When Fe2O3 and CeO2 were added separately, there was a decline in NO and CO emission (NO: 10.11% vs. 6.48%, CO: 7.18% vs. 5.28%). Meanwhile, the mixture of Fe2O3 and CeO2 caused a great decline in the total amounts of NO and CO emission (NO: 20.70%, CO: 16.33%). The denitration effect is ascribed to the homogeneous reduction of NO by CO, enhanced by adding the catalysts CeO2 and Fe2O3. Fe2O3 and CeO2 are catalytically active in promoting not only coke combustion but also NO reduction. Fe2O3 and CeO2 are associated, synergically catalyzing the semi-coke combustion.

Hydrogen storage performance of the as-milled Y[sbnd]Mg[sbnd]Ni alloy catalyzed by CeO2

The YMgNi-based YMg11Ni + 5 wt%CeO2 (named YMg11Ni5CeO2) alloys were prepared by using mechanical ball milling. The influences of CeO2 on the structure and gaseous hydrogen storage performance of YMg11Ni alloy were studied systematically. The structures of sample alloy were determined by X-ray diffraction (XRD) and high resolution transmission electron microscope (HRTEM). The gaseous hydrogen storage performances were tested by using an automatically controlled Sieverts apparatus. The dehydrogenation performance was studied by thermogravimetry (TG) and differential scanning calorimetry (DSC). The hydrogen desorption activation energy was calculated by adopting Kissinger methods. The results show that adding CeO2 into YMg11Ni can lower the hydrogen storage thermodynamics slightly and increase the hydrogen absorption/desorption rate obviously. Moreover, the hydrogen desorption activation energy (Ede(k)) of the alloys is 91.53 kJ mol−1 for YMg11Ni alloy and 74.89 kJ mol−1 for YMg11Ni5CeO2 alloy, respectively. This is because the hydrogen desorption kinetic of the alloy is improved by adding catalyst CeO2.

La1-xCaxMn1-yAlyO3 perovskites as efficient catalysts for two-step thermochemical water splitting in conjunction with exceptional hydrogen yields

Solar-driven thermochemical water splitting represents one efficient route to the generation of H2 as a clean and renewable fuel. Due to their outstanding catalytic abilities and promising solar fuel production capacities, perovskite-type redox catalysts have attracted significant attention in this regard. In the present study, the perovskite series La1-xCaxMn1-yAlyO3 (x, y = 0.2, 0.4, 0.6, or 0.8) was fabricated using a modified Pechini method and comprehensively investigated to determine the applicability of these materials to solar H2 production via two-step thermochemical water splitting. The thermochemical redox behaviors of these perovskites were optimized by doping at either the A (Ca) or B (Al) sites over a broad range of substitution values, from 0.2 to 0.8. Through this doping, a highly efficient perovskite (La0.6Ca0.4Mn0.6Al0.4O3) was developed, which yielded a remarkable H2 production rate of 429 μmol/g during two-step thermochemical H2O splitting, going between 1400 and 1000 °C. Moreover, the performance of the optimized perovskite was found to be eight times higher than that of the benchmark catalyst CeO2 under the same experimental conditions. Furthermore, these perovskites also showed impressive catalytic stability during two-step thermochemical cycling tests. These newly developed La1-xCaxMn1-yAlyO3 redox catalysts appear to have great potential for future practical applications in thermochemical solar fuel production.

Hydriding/dehydriding properties of NdMgNi alloy with catalyst CeO2

Hydrogen storage composites Nd2Mg17-50 wt.%Ni-x wt.%CeO2 (x=0, 0.5, 1.0, 1.5, 2.0) were obtained by induction-ball milling method. The catalytic effect of CeO2 on hydriding kinetics of Nd2Mg17-50 wt.%Ni composite was investigated. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) analyses showed that Nd2Mg17-50 wt.%Ni alloy had a multiphase structure, consisting of NdMg12, NdMg2Ni, Mg2Ni and Ni phases and the addition of catalyst CeO2 prompted the composites to be partly transformed into amorphous strucutre. The CeO2 improved the maximum hydrogen capacity of Nd2Mg17-50 wt.%Ni alloy from 3.192 wt.% to 3.376 wt.% (x=1.0). What's more, the increment of diffusion coefficient D led to the faster hydriding kinetics, which was calculated by Avrami-Erofeev equation. The dehydrogenation temperature reduced from 515.54 to 504.72 K was mainly caused by the decrease of activation energy from 93.28 to 69.36 kJ/mol, which was proved by the Kissinger equation.

ChemInform Abstract: Transformylating Amine with DMF to Formamide over CeO2 Catalyst.

AbstractThe acid‐base bifunctional property of the heterogeneous catalyst CeO2 is crucial and it is the only heterogeneous catalytic system reported to accomplish this reaction in good yields.

96/01859 Operating procedure for fluidized-bed reactor for gasification of carbonaceous fuels

Solar-driven thermochemical water splitting represents one efficient route to the generation of H2 as a clean and renewable fuel. Due to their outstanding catalytic abilities and promising solar fuel production capacities, perovskite-type redox catalysts have attracted significant attention in this regard. In the present study, the perovskite series La1-xCaxMn1-yAlyO3 (x, y = 0.2, 0.4, 0.6, or 0.8) was fabricated using a modified Pechini method and comprehensively investigated to determine the applicability of these materials to solar H2 production via two-step thermochemical water splitting. The thermochemical redox behaviors of these perovskites were optimized by doping at either the A (Ca) or B (Al) sites over a broad range of substitution values, from 0.2 to 0.8. Through this doping, a highly efficient perovskite (La0.6Ca0.4Mn0.6Al0.4O3) was developed, which yielded a remarkable H2 production rate of 429 μmol/g during two-step thermochemical H2O splitting, going between 1400 and 1000 °C. Moreover, the performance of the optimized perovskite was found to be eight times higher than that of the benchmark catalyst CeO2 under the same experimental conditions. Furthermore, these perovskites also showed impressive catalytic stability during two-step thermochemical cycling tests. These newly developed La1-xCaxMn1-yAlyO3 redox catalysts appear to have great potential for future practical applications in thermochemical solar fuel production.