CeO2 Nanosheets Research Articles

Surfacial proton conducting CeO2 nanosheets

Proton conducting ceramic fuel cells (PCFCs) have been attracting much more attentions due to is affordable ionic conductivity lower operating temperatures (<600 °C). CeO2 nanosheets expose mainly to the (111) plane exhibit a super proton conductivity of 0.3 S cm−1 and a maximum power density of 948 mWcm−2 at 550 °C. In these two morphologies of CeO2, the difference in Ce3+/Ce4+ ratios and the formation of oxygen vacancies on the surface are mainly responsible for proton transport. Theoretical calculation proves that protons can move more easily on the CeO2 (111) facet with smaller binding energy (0.14 eV) and lower energy barrier for H–O formation (1.7 eV) than on other facets, also superior proton conduction for the nanosheet morphology over the nano-particles. This work has developed a morphological methodology for high proton surface conduction to design highly efficient ionic transport for advanced CFCs and electrochemical devices.

Atomically dispersed Ni catalyst to boost weak sunlight-driven CO2 hydrogenation with 100% CO selectivity

Ni based catalysts are highly stable and active for CO2 hydrogenation as CO, but the CO selectivity can not reach 100 %, which has not been realized so far. In this work, theoretical calculations are used to predict that Ni single atoms can cause Pauli incompatibility to block the CH4 production path of CO2 hydrogenation, so as to achieve 100 % CO produced selectivity of Ni based catalysts. Based on theoretical prediction, Ni single atoms supported on CeO2 nanosheets (SA Ni/CeO2) are synthesized for CO2 hydrogenation, which displays a high CO production rate of 47.06 mmol·g−1·h−1 at 500 °C and an unprecedented 100 % CO selectivity. Further, the SA Ni/CeO2 supported by homemade solar heating conversion device exhibits a CO production rate of 23.1 mmol·g−1·h−1 with 100 % CO selectivity from the solar heating CO2 hydrogenation under 3 suns irradiation, 4.7 times higher than the record of weak sunlight driven CO production.

The tuned selective catalytic reduction behaviors of NO over the Pt/CeO2 catalysts by preferentially exposing different facets of CeO2 supports

For the Pt catalysts supported on CeO2 nanosheet (NS), nanopolyhedron (NP) and nanorod (NR) with preferentially exposed {100}, {111} and {110} facets, respectively, the NO conversion and N2 selectivity for NO + CO reaction at 100–250 °C exhibit the order as Pt/CeO2-NS{100} > Pt/CeO2-NP{111} > Pt/CeO2-NR{110}. The higher surface concentration of oxygen vacancies on CeO2 (NS) can promote the dissociation of NO and result in the highest performance of Pt/CeO2-NS{100} catalyst. Moreover, CO intensively chemisorbs on the Pt2+ ions on CeO2 (NR) support, suppressing the dissociative chemisorption of NO and leading to lower reaction performance of Pt/CeO2-NR{110} catalyst.

Formulation of Bismuth (Bi2O3) and Cerium Oxides (CeO2) Nanosheets for Boosted Visible Light Degradation of Methyl Orange and Methylene Blue Dyes in Water

Annealing of periodic mesoporous organosilica supported with bismuth (Bi@PMOS) and cerium (Ce@PMOS) nanoparticles was carried out to derive bismuth oxide (Bi2O3) and cerium oxide (CeO2) nanosheets. The hydrothermal sol-gel method was used to synthesize hexagonal Bi@PMOS and Ce@PMOS. These PMOS provided an opportunity for bismuth and cerium to retain a hexagonal configuration alongside their traditional crystalline phases (tetragonal and cubic) in Bi2O3 and CeO2 nanosheets. All produced materials were found to be dynamic under sunlight irradiation for the degradation of methylene blue (MB) and methyl orange (MO). However, the Bi2O3 and CeO2 nanosheets showed better potential and photo-catalytic performances than Bi@PMOS and Ce@PMOS due to the presence of the unique blend of crystalline phases. The synthesized Bi@PMOS, Ce@PMOS, Bi2O3, and CeO2 were structurally characterized by FTIR and XRD techniques. These showed characteristic vibrations of successfully loaded bismuth and cerium with hexagonal symmetry. EDX results confirmed the elemental detection of bismuth and cerium, while SEM images revealed the nanosheets in the synthesized materials. The optical response and detection of reactive species were carried out by photoluminescence (PL) and showed emissions at 700 nm. The PL data were also used to calculate band gaps of 3.72, 3.70, 3.35, and 2.88 eV for Ce@PMOS, Bi@PMOS, CeO2, and Bi2O3, respectively. A UV/visible spectrophotometer scanned the photocatalytic competences of the synthesized nanomaterials through the degradation of MB and MO dyes. Then, 10 mg of Bi@PMOS and Ce@PMOS degraded 15 mg and 8.4 mg of MB and 10.8 mg and 8 mg of MO, respectively, in 20 mg/L solutions. However, equivalent quantities of Bi2O3 and CeO2 (10 mg of each) exhibited more efficient photocatalysis of the 20 mg/L solutions of MB and MO, degrading 18.4 mg and 15.4 mg, and 12.4 mg and 17 mg, respectively, in only 1 h. The Bi2O3 and CeO2 photocatalysts were regenerated and their photodegradation results were also recovered. Bi2O3 and CeO2 showed only 10% and 8% (for MB), and 8% and 10% (for MO) decline in catalytic efficiency, respectively, even after four consecutive recycles. These results demonstrate that these materials are dynamic, long-lasting photocatalysts for the rapid degradation of azo dyes in contaminated water.

Low Temperature Thermal and Solar Heating Carbon‐Free Hydrogen Production from Ammonia Using Nickel Single Atom Catalysts

AbstractCatalytic splitting NH3 to H2 is one of the foundations for building a carbon‐free H2 energy system but requires NH3 splitting catalysts that are highly active and durable at low temperatures. Although various non‐noble catalysts have been designed, NH3 splitting still operates at relatively high temperatures (600–850 °C). Herein, theoretical calculations predict that the Ni single atoms can change the bonding mode of NiN from covalent bond to ionic bond to boost the NH3 splitting activity. Further, Ni single atoms supported on CeO2 nanosheets (SA Ni/CeO2) are synthesized by the sol–gel method, which exhibits a robust 3.544 mmol g−1 min−1 of H2 yield speed of NH3 splitting at 300 °C, superior to all non‐noble catalysts and most of the noble catalysts. Combing with the homemade solar heating device, the one sun‐driven NH3 splitting over SA Ni/CeO2 shows a stable H2 yield of 1.58 mmol g−1 min−1, 100 times the record value of advanced weak solar‐powered NH3 splitting, demonstrating the potential for practical application in carbon‐free H2 systems.

Solution Plasma Processing Single‐Atom Au1 on CeO2 Nanosheet for Low Temperature Photo‐Enhanced Mars–van Krevelen CO Oxidation

AbstractCreating oxygen vacancies in metal oxide support holds promise in anchoring and stabilizing single atom metals, activating the lattice oxygen of metal oxide and accelerating Mars–van Krevelen (MvK) catalytic oxidation. However, it is challenging to achieve nearly 100% trapping of single atom metal in solution by oxygen vacancy typed metal oxide, resulting from the difficulty in synchronized formation of oxygen vacancies and capture of the single atom metal. In this study, a solution plasma process (SPP) is developed, enabling ≈99% trapping of single atom Au by using oxygen vacancy typed CeO2 nanosheet in 2 min. Owing to the large number of electrons and free radicals present in the plasma region, the SPP can simultaneously reduce HAuCl4 to single‐atom Au and bring oxygen vacancies as anchoring sites onto CeO2. The catalytic test of CO oxidation assisted by solar light can reach a conversion of 91.7% with a high turnover frequency of 1.3 s−1 at room temperature, far exceeding the requirements for the “150 °C challenge.” A photo‐enhanced MvK pathway is proposed for the superior performance of Au1/CeO2. This study not only explores a novel solution approach to prepare single‐atom metal catalysts, but also provides an effective strategy for efficient low‐temperature catalytic oxidation.

Photocatalytic degradation of Estrone and Congo red by the magnetic antibacterial photocatalyst g-C3N4/CeO2/M-rGO under visible light and optimization by Box-Behnken statistical design (BBD)

Construction of multi-interface contact step-scheme photocatalyst is a promising pathway to achieve high-electron transfer efficiency for photodegradation Estrone and Congo red (CR). In this work, g-C3N4 was selected as the main component, CeO2 nanosheets with unique Ce4+→Ce3+ conversion property and M-rGO were loaded on the surface of g-C3N4 to construct magnetic photocatalyst, whose structure imparted reusability by magnetic retrieval and at the same time M-rGO acted as an efficient host for g-C3N4/CeO2 composite photocatalyst. The photocatalytic performances were investigated with Estrone and CR, and the results showed that the composite photocatalyst g-C3N4/CeO2/M-rGO could degrade 71% of Estrone and 92% of CR. Free radical scavenger test showed that superoxide and hydroxyl radical species played a major role in the degradation. Furthermore, it was demonstrated that the magnetic photocatalyst g-C3N4/CeO2/M-rGO possessed strong antibacterial properties against Proteus mirabilis. A three-factor-three-level Box-Behnken design (BBD) was selected to optimize three greatly influential parameters: light irradiation time (min), the mass of photocatalyst (mg) and pollution concentration (ppm) by responding surface methodology. It was expected that the g-C3N4/CeO2/M-rGO can be used as a magnetic photocatalyst to achieve its valorization, which has very broad development prospects in the field of environmental remediation or catalysis.

Coupling of SiC and CeO2 nanosheets to enhance solar energy utilization and optimize catalytic ozonation

The coupling of solar energy conversion and catalytic ozonation is an effective way to eliminate volatile organic compounds with high-efficiency and low-energy-consumption. In this work, we presented a non-noble-metal SiC/CeO2 system for solar-light-assisted catalytic ozonation of toluene. Temperature and light-controlled experiments and atmosphere surface photovoltage measurement were conducted to evaluate photothermal and photoelectric processes. Results show that toluene removal and mineralization efficiencies of 25%SiC-CeO2 were 69.7% and 67.1%, respectively, under full-spectrum illumination with an hourly space velocity of 6000 /h. The SiC enhanced the conversion of incident visible and infrared (IR) light to heat, thereby increasing the reaction temperature over 25%SiC-CeO2. Moreover, SiC transferred electrons to CeO2 in 25%SiC-CeO2, generating more surface Ce3+ sites and promoting charge carriers separation efficiency. Given these characteristics, 25%SiC-CeO2 exhibited outstanding performance in toluene mineralization, even better than Pd-loaded CeO2.

CeO2 nanosheets with anion-induced oxygen vacancies for promoting photocatalytic toluene mineralization: Toluene adsorption and reactive oxygen species

The deep oxidation of toluene is recognized as a major challenge for photocatalytic oxidation of toluene. Herein, we introduced oxygen vacancies into CeO2 nanosheets through novel anion-removal of Ce-LDH, with the calcining temperatures of 750, 850, 950 °C. The photocatalytic toluene performance was ordered by CeMO-850 > CeMO-750 > CeMO-950, and CeMO-850 had better activity than P25, common CeO2, and CeO2-H2. Different reaction pathways were founded on CeMO photocatalysts, i.e., on CeMO-950 and CeMO-750, the cresol and hydroquinone intermediates were observed, which hindered toluene adsorption/activation and were hard to deep-mineralization. Whereas, more benzoic acid, open-loop oxygen-containing intermediates were observed on CeMO-850, which were resulted from its oxygen vacancies (Ov), i.e., surface Ov and Ce3+ were beneficial for toluene adsorption, B acid sites and active radicals’ generation, respectively, and bulk Ov were helpful for oxygen mobility and efficient deep-mineralization. The mechanism of Ov generation and toluene degradation were proposed.

Defect-rich Fe-doped CeO2 nanosheets as effective oxygen evolution electrocatalysts

Designing nanocatalysts with defect architectures and heteroatom doping can increase the performance of the electrocatalyst used for OER. With the assistance of microwave strategy, we synthesized two-dimensional (2D) Fe-doped CeO2 nano-sheets (Fe/CeO2 NSs) containing oxygen vacancies (Ov) for oxygen evolution reaction (OER) electrocatalyst by calcining Fe-doped Ce(C2O4)3 as precursor at different temperatures. Benefiting from lattice defects derived from Ov and doped Fe, the electrocatalysis of Fe/CeO2-400 NSs shows a much smaller Tafel slope of 46 mV·decade-1 than that of pure CeO2. Furthermore, the polarization curves only slightly changed after 1000 cyclic voltammetry (CV) cycles which also confirmed the good stability of the Fe/CeO2-400 NSs. The outstanding electrocatalytic properties as well as the stability of Fe/CeO2 NSs should be attributed to the active sites contributed by the defective regions on the nanosheets, while Fe is doped into the CeO2 lattice as a heteroatom and affects the electronic structure, improving the overall OER performance.

Mechanistic insight into the dynamic transformation of acid sites on ceria supported molybdenum oxide catalyst for NOx reduction

Acidity is a crucial factor limiting the application of ceria-based catalyst for selective catalytic reduction (SCR) of NOx with NH3. Unravelling the participation mechanism of acid sites on ceria-based catalyst is imperative but still lacking. Herein, by tuning the electronic interaction between MoOx and CeO2 nanosheet with numerous pits (P-CeO2) via controlling the number of surface pits of P-CeO2, we demonstrate that electronic interaction strongly determines the acidity properties of catalyst to modulate the catalytic performance. The MoOx/P-CeO2 exhibits much better catalytic activity, N2 selectivity and tolerance to SO2 and H2O than MoOx/CeO2 with few pits in a temperature range of 250–400 °C with a gas hourly space velocity (GHSV) of 60,000 h−1, which is due to the highly dispersion of Mo-O-Mo structure over P-CeO2 as determined by Raman. Furthermore, XPS and DFT calculations demonstrate that electrons transfer from P-CeO2 to MoOx result in a unique dynamic transformation from Brønsted acid site to Lewis acid site, enhancing the catalytic activity. This work increases the acidity sites on the catalyst by regulating the electron oxide-support interaction, which provides a new strategy for designing highly efficient ceria-based SCR catalysts.

Selective CO2 Photoreduction to CH4 via Pdδ+‐Assisted Hydrodeoxygenation over CeO2 Nanosheets

AbstractHere, noble‐metal‐doped two‐dimensional metal oxide nanosheets are designed to realize selective CO2 photoreduction to CH4. As a prototype, Pd‐doped CeO2 nanosheets are fabricated, where the active sites of Pdδ+ (2&lt;δ&lt;4) and Ce3+−Ov are revealed by quasi in situ X‐ray photoelectron spectra and in situ electron paramagnetic resonance spectra. Moreover, in situ Fourier‐transform infrared spectra of D2O photodissociation and desorption verify the existence of the Pd−OD bond, implying that Pdδ+ sites can participate in water oxidation to deliver H* species for facilitating the protonation of the intermediates. Furthermore, theoretical calculations suggest the Pd doping could regulate the formation energy barrier of the key intermediates CO* and CH3O*, thus making CO2 reduction to CH4 become the favorable process. Accordingly, Pd‐doped CeO2 nanosheets achieve nearly 100 % CH4 selectivity of CO2 photoreduction, with the raising CH4 evolution rate of 41.6 μmol g−1 h−1.

Selective CO2 Photoreduction to CH4 via Pdδ+ -Assisted Hydrodeoxygenation over CeO2 Nanosheets.

Here, noble-metal-doped two-dimensional metal oxide nanosheets are designed to realize selective CO2 photoreduction to CH4 . As a prototype, Pd-doped CeO2 nanosheets are fabricated, where the active sites of Pdδ+ (2<δ<4) and Ce3+ -Ov are revealed by quasi in situ X-ray photoelectron spectra and in situ electron paramagnetic resonance spectra. Moreover, in situ Fourier-transform infrared spectra of D2 O photodissociation and desorption verify the existence of the Pd-OD bond, implying that Pdδ+ sites can participate in water oxidation to deliver H* species for facilitating the protonation of the intermediates. Furthermore, theoretical calculations suggest the Pd doping could regulate the formation energy barrier of the key intermediates CO* and CH3 O*, thus making CO2 reduction to CH4 become the favorable process. Accordingly, Pd-doped CeO2 nanosheets achieve nearly 100 % CH4 selectivity of CO2 photoreduction, with the raising CH4 evolution rate of 41.6 μmol g-1 h-1 .

Oxy-Anionic Doping: A New Strategy for Improving Selectivity of Ru/CeO2 with Synergetic Versatility and Thermal Stability for Catalytic Oxidation of Chlorinated Volatile Organic Compounds.

Understanding the formation and inhibition of more toxic polychlorinated byproducts from the catalytic oxidation elimination of chlorinated volatile organic compounds (Cl-VOCs) and unveiling efficient strategies have been essential and challenging. Here, RuOx supported on CePO4-doped CeO2 nanosheets (Ru/Pi-CeO2) is designed for boosting catalytic oxidation for the removal of dichloromethane (DCM) as a representative Cl-VOC. The promoted acid strength/number and sintering resistance due to the doping of electron-rich and thermally stable CePO4 are observed along with the undescended redox ability and the exposed multi-active sites, which demonstrates a high activity and durability of DCM oxidation (4000 mg/m3 and 15,000 mL/g·h, stable complete-oxidation at 300 °C), exceptional versatility for different Cl-VOCs, alkanes, aromatics, N-containing VOCs, CO and their multicomponent VOCs, and enhanced thermal stability. The suppression of polychlorinated byproducts is determined over Ru/Pi-CeO2 and oxy-anionic S, V, Mo, Nb, or W doping CeO2, thus the oxy-anionic doping strategy is proposed based on the quenching of the electron-rich oxy-anions on chlorine radicals. Moreover, the simple mechanical mixing with these oxy-anionic salts is also workable even for other catalysts such as Co, Sn, Mn, and noble metal-based catalysts. This work offers further insights into the inhibition of polychlorinated byproducts and contributes to the convenient manufacture of monolithic catalysts with superior chlorine-poisoning resistance for the catalytic oxidation of Cl-VOCs.

Selective laser welding in liquid: A strategy for preparation of high-antibacterial activity nanozyme against Staphylococcus aureus

Nanozyme was considered as one of the most promising substitutes for antibiotics, due to the selective catalysis for pathogens. In this work, a high-antibacterial activity SOD-like nanozyme based on hybrid Ag/CeO2 nanocomposite was facilely prepared by using an innovative approach of selective laser welding in liquid. This prepared nanozyme displayed a high antimicrobial effect against Staphylococcus aureus under visible light illumination, the sterilization rate as high as 82.4%, which was 2.93 and 2.99 times higher than those of pure Ag and pure CeO2, respectively. The enhanced antibacterial activity was attributed to the anchoring of Ag nanospheres on the surface of CeO2 nanosheets, which induced the reduction of CeO2 bandgap and boosted the visible light harvesting. Therefore, the charge carriers can be effectively stimulated to produce abundant reactive oxygen species on the Ag/CeO2 nanocomposite via a SOD-like route. This work demonstrated a facile strategy for the preparation of high-antibacterial activity nanozyme, giving it great potential for scalable application in the biomedical and pharmaceutical industry.

Novel Pd/Al2O3–CeO2 Nanosheets for One-Pot Synthesis of Methyl Isobutyl Ketone from Acetone

Novel Pd/Al2O3–CeO2 Nanosheets for One-Pot Synthesis of Methyl Isobutyl Ketone from Acetone

Ultra-active Ru supported on CeO2 nanosheets for catalytic combustion of Propane: Experimental insights into interfacial active sites

Catalytic oxidation of propane as a representative molecule of light hydrocarbons (LHs) is of special interest for energy utilization and pollution abatement but is challengeable due to its stable C–H bonds. Here, Ru supported on porous and defect-rich CeO2 nanosheets catalysts were prepared and investigated for catalytic oxidation of propane, and the Ru/CeO2 catalyst using chlorine-free Ru precursor (RuN/CeNS) presented an ultra-high activity with complete conversion at 150 °C. A series of well-designed experiments and characterizations illustrated that the high-density and uniform Ru-O-Ce interfaces were determinant for propane oxidation due to the possible asymmetric bridged adsorption and activation. The presence of chlorine species suppressed the dispersion of RuOx species and the formation of Ru-O-Ce interfaces, which also accelerated the sintering of CeO2 and Ru-O-Ce interfaces at high temperatures. This work highlighted the experimental insights into the active interfacial sites of ultra-active Ru/CeO2 for propane oxidation. It contributed to an in-depth understanding of the activation of C–H bonds in LHs and the preparation of supported noble metal catalysts.

Self-template-oriented synthesis of lead-free perovskite Cs3Bi2I9 nanosheets for boosting photocatalysis of CO2 reduction over Z-scheme heterojunction Cs3Bi2I9/CeO2

Lead halide perovskite (LHP) nanocrystals have been intensely studied as photocatalysts for artificial photosynthesis in recent years. However, the toxicity of lead in LHP seriously limits their potential for widespread applications. Herein, we first present the synthesis of 2D lead-free halide perovskite (Cs3Bi2I9) nanosheets with self-template-oriented method, in which BiOI/Bi2O2.7 nanosheets were used as the template and Bi ion source simultaneously. Through facile electrostatic self-assembly strategy, a Z-scheme heterojunction composed of Cs3Bi2I9 nanosheets and CeO2 nanosheets (Cs3Bi2I9/CeO2-3:1) was constructed as photocatalyst for the photo-reduction of CO2 coupled with the oxidation of H2O. Due to the matching energy levels and the close interfacial contact between Cs3Bi2I9 and CeO2 nanosheets, the separation efficiency of the photogenerated carriers in Cs3Bi2I9/CeO2-3:1 composite was significantly improved. Consequently, the environment-friendly halide perovskite heterojunction Cs3Bi2I9/CeO2-3:1 presents impressive photocatalytic activity for the reduction of CO2 to CH4 and CO with an electron consumption yield of 877.04 μmol g−1, which is over 7 and 15 times higher than those of pristine Cs3Bi2I9 and CeO2 nanosheets, exceeding the yield of other reported bismuth-based perovskite for photocatalytic CO2 reduction.

Ultra-Active Ru Supported on Ceo2 Nanosheets for Catalytic Combustion of Propane: Experimental Insights into Interfacial Active Sites

Ultra-Active Ru Supported on Ceo2 Nanosheets for Catalytic Combustion of Propane: Experimental Insights into Interfacial Active Sites

Coke and sintering resistant nickel atomically doped with ceria nanosheets for highly efficient solar driven hydrogen production from bioethanol

Ni single atoms doped with CeO2 nanosheets combined with a Ti2O3 based photothermal device showed 3 Suns driven ESR with 462 °C temperature, 519 mmol g−1 h−1 H2 production rate, 16.7% solar-to-fuel efficiency and 60 hours of stable operation.