CeO2 Nanosheets Research Articles

Sensitization of AgInS2 nanoparticles enhances photoelectrochemical water splitting performance of CeO2 nanosheet arrays photoanode

In this study, we present a promising CeO2/AgInS2 heterostructure photoanode for photoelectrochemical (PEC) water decomposition. Mott-Schottky analysis is employed to confirm the formation of a type-II heterostructure between AgInS2 nanoparticles and CeO2 nanosheet arrays (NSAs) fabricated through electrochemical deposition and successive ionic layer adsorption and reaction. Electrochemical impedance spectroscopy, photoluminescence analysis, and Bode diagram spectroscopy confirm the effective charge carrier separation and significantly prolonged the charge lifetime of the CeO2/AgInS2 heterojunction photoanode. Consequently, the maximum photocurrent density of the constructed CeO2/AgInS2 photoanode relative to Ag/AgCl under zero bias test conditions is 69.8 times higher than the pure CeO2 NSAs. Additionally, the charge transfer mechanism is further verified by the calculated work function and differential charge density of CeO2/AgInS2 heterojunction. This study provides a valuable reference for the synthesis and preparation of heterojunction photoanode for efficient PEC water decomposition.

Boosted antibiotic elimination over 2D/2D mesoporous CeO2/BiOCl S-scheme photocatalyst

Exploring efficient photocatalysts holds significant importance for the prevention and treatment of antibiotic pollution. This research reports a 2D/2D CeO2/BiOCl S-scheme photocatalyst constructed by mesoporous CeO2 and BiOCl nanosheets (NSs). Efficient charge separation and transfer was achieved by the synergistic effect of large-area contact and S-scheme charge transfer mechanism, which significantly enhanced the photocatalytic performance of CeO2/BiOCl. Experimental results demonstrated that the CeO2/BiOCl photocatalyst displayed superior photocatalytic activity to the individual components, which could efficiently eliminate four types of antibiotics, namely tetracycline (TC), chlortetracycline (CTC), doxycycline (DOC), and oxytetracycline (OTC) under UV light irradiation. Particularly, the sample of 0.4CeO2/BiOCl exhibited the highest catalytic efficiency, with a TC degradation rate constant of 0.01524 min−1, which was 1.85 and 22.74 times higher than that of single CeO2 and BiOCl, respectively. Moreover, liquid chromatograph-mass spectrometer (LC-MS) analysis is employed to reveal the degradation pathways of TC. This work offers an insightful idea for the fabrication of novel S-scheme photocatalysts applied in environmental purification.

Enriched Surface Oxygen Vacancies of CeO2 Nanosheets: Surfactant Free Synthesis at Room Temperature and its Enhanced Anti‐bacterial Property

AbstractIn this work, flower shape cerium oxide (CeO2) nanosheets were synthesized at room temperature through a facile precipitation method without adding any surfactant. The synthesized nanosheets were characterized by scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM), Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffractometry (XRD) and X‐ray photoelectron spectroscopy (XPS). Results showed that the CeO2 nanosheets form a petal‐like morphology and have fluorite crystal structure with no crystal phase impurity while the average crystallite size of nanosheets i. e. ~10 nm. The CeO2 nanosheets are applied as an antimicrobial agent and the antibacterial property against G+ and G− bacteria i. e. (E. coli and S. Aureus) were studied. The obtained results showed that the synthesized CeO2 nanosheets had good antibacterial performance at different concentrations, which should be attributed to the reversible Ce3+/Ce4+ valence states and greater oxygen vacancies. XPS study of CeO2 nanosheets after antibacterial test confirmed the existence of Ce3+ ions and oxygen vacancies. CeO2 nanosheets have showed the greater potential as antibacterial nanomaterials against both the bactericides.

Investigation into the photothermal catalytic CO2 decomposition over CeO2 with different morphologies: Behaviors of oxygen vacancies

CO2 is a viable renewable energy source, as global CO2 emissions are perennially increasing. The decomposition of CO2 to CO and O2 through high-temperature cracking of metal oxides via a two-step thermochemical cycle has been an effective strategy to reduce CO2 concentrations in the atmosphere. However, this thermochemical cycle requires a high reaction temperature (1273 K). Hence, in this study, we investigated photothermal CO2 decomposition over three CeO2 catalysts with different morphologies: porous CeO2 nanosheets (2D-CeO2), cubic-shaped CeO2 (C-CeO2), and octahedral CeO2 (O-CeO2). The photothermal synergistic effect eliminated the necessity of high temperatures, where light illumination increased the generation of oxygen vacancies and electron transfer to promote CO2 decomposition. The maximum rate of CO production by 2D-CeO2 at 250 °C was 69 μmol g-1h−1, which is significantly higher than those of O-CeO2 (47 μmol g-1h−1) and C-CeO2 (19 μmol g-1h−1). However, no activity was observed in dark conditions, even at 250 °C. In-situ DRIFTS, quasi in-situ EPR, XPS, and Ar-TPD experiments revealed that light irradiation promotes the production of oxygen vacancies on the catalyst surface and generates the intermediate CO2•− species, which cleave the C=O bonds and CO2 conversion, while temperature promotes the adsorption of CO2 on the catalyst surface and facilitates electron transfer. DFT calculations revealed the differences in oxygen vacancy formation and CO2 adsorption among various exposed crystal facets of CeO2. These findings provide new avenues for CO2 decomposition based on the adsorption and activation of CO2 on metal oxide surfaces and the low-temperature synergistic photothermal effect.

Lamellar cross-linking Ni/CeO2 as an efficient and durable catalyst for dry reforming of methane

Dry reforming of methane provides a prospective process for converting greenhouse gases into syngas but suffers from the coking and sintering of catalyst at high operating temperatures. Here we report a lamellar cross-linking Ni/CeO2 catalyst that shows durable performance with 73 % CO2 and 60 % CH4 conversions for DRM at 700 °C in a continuous operation of 50 h. The sintering of Ni particles is inhibited due to the confined migration and aggregation of Ni nanoparticles provided by the lamellar CeO2 nanosheets. Meanwhile, the presence of these CeO2 nanosheets facilitates the release of lattice oxygen and the formation of oxygen vacancies, thereby generating more reactive oxygen species, as revealed by the characterization of Raman, XPS, H2-TPR and O2-TPD. The catalyst characterization using TGA and N2-TP indicates that the reactive oxygen species can realize the in-situ gasification of carbon deposition, thus achieving a balance between the rate of coke formation and carbon gasification. Due to the dynamic balance of carbon deposits, no further accumulation of carbon deposition is observed during the DRM test from 10 h to 50 h.

Atomic Pt Sites Anchored in the Interface between Grains on Vacancy-Enriched CeO2 Nanosheets: One-Step Precursor Combustion Synthesis.

Atomic metal catalysts have unique electronic, structural, and catalytic properties, which are widely used in the field of catalysis. However, designing new simple synthesis methods to fabricate atomic metal catalysts is a challenge in catalytic applications. Herein, a one-step precursor combustion strategy is presented that starts directly from precursors of metal salts, using a spontaneous combustion process convert platinum nitrate to atomic Pt sites. The atomic Pt sites with low valence are anchored in the formed interface between grains on vacancy-enriched CeO2 nanosheets. The obtained Pt/CeO2-2 catalyst exhibits much higher three-way catalytic activities at low temperatures than Pt/CeO2-C catalysts prepared using the traditional impregnation method. Density functional theory calculations show that the generated lower valent Pt atoms in the CeO2 interface promote catalytic activity through reducing the energy barrier, and lead to an overall improvement of three-way catalytic activities. This facile strategy provides new insights into the study of the properties and applications of atomic noble metal catalysts.

Cobalt enhanced (H/C-CdS)/CeO2 activity for visible light catalytic oxidation of formaldehyde at room temperature

The visible light catalytic oxidation of formaldehyde (HCHO) at room temperature is of great interest for improving the indoor air quality. Here, a cobalt (Co)-doped CdS-based catalyst ((H/C-CdS)/CeO2) with high visible light catalytic activity was successfully synthesized for HCHO removal at room temperature. Co addition enhanced the catalytic activity of (H/C-CdS)/CeO2, and the HCHO conversion rate reached 99.5 % for a 1 mg/L aqueous HCHO solution on the Co–(H/C-CdS)/CeO2 catalyst after 1 h at room temperature under visible light, which was greater than that of (H/C-CdS)/CeO2 (92.0 %). The (H/C-CdS)/CeO2 and Co–(H/C-CdS)/CeO2 catalysts were systemically characterized, and the results showed that the interfacial phase junction between the hexagonal (H) and cubic (C) phases of the CdS nanoparticles (NPs) and the synergistic effect of the type II heterojunction between the CdS NPs and CeO2 nanosheets (NSs) promoted the separation of e-/h+. Moreover, the addition of Co species strongly promoted the separation of photogenerated carriers. The excellent photocatalytic activity was attributed to the good dispersion of CdS NPs, which broadened the light absorption range, exposed more active sites, and provided close contact, decreasing the migration distance of photogenerated electron-hole pairs. After that, the visible light catalytic oxidation mechanism of HCHO on both (H/C-CdS)/CeO2 and Co–(H/C-CdS)/CeO2 followed the reaction pathway of HCHO to (CO2 + H2O).

Plasma-Engineered CeOx Nanosheet Array with Nitrogen-Doping and Porous Architecture for Efficient Electrocatalysis.

Surface engineering has been proved efficient and universally applicable in improving the performance of CeO2 in various fields. However, previous approaches have typically required high-temperature calcination or tedious procedures, which makes discovery of a moderate and facile modification approach for CeO2 an attractive subject. In this paper, porous CeO2 nanosheets with effective nitrogen-doping were synthesized via a low-temperature NH3/Ar plasma treatment and exhibited boosted hydrogen evolution reaction performance with low overpotential (65 mV) and long-term stability. The mechanism of the elevated performance was investigated by introducing Ar-plasma-treated CeO2 with no nitrogen-doping as the control group, which revealed the dominant role of nitrogen-doping by providing abundant active sites and improving charge transfer characteristics. This work illuminates further investigations into the surface engineering methodologies boosted by plasma and the relative mechanism of the structure-activity relationship.

A novel 2D/2D MoS2/CeO2 nanohybrid and its lubricating mechanism in green rapeseed oil

The incomplete stacking of two distinct types of two-dimensional (2D) layered materials to form a 2D/2D nanohybrid, accompanied by the generation of ultra-low friction at the interface, offers a novel solution for designing lubricants with superior tribological performance. This work utilized a facile and gentle method to synthesize MoS2 and CeO2 nanosheets with varying sizes, which were then stacked to form 2D/2D nanohybrid. This nanohybrid was employed as dispersant additives in eco-friendly lubricant to effectively reduce friction. The tribological testing results revealed that this nanohybrid exhibited remarkable reductions in the average coefficient of friction (COF) and wear rate of rapeseed oil, compared to single MoS2 or CeO2. At a 1.5 wt% addition of MoS2/CeO2, the average COF and wear rate decreased to the lowest value, respectively. Moreover, the frictional behaviors of the rapeseed oil containing MoS2/CeO2 nanohybrid under various sliding conditions were explored as well. By analyzing the microstructure and composition of the counterparts’ surfaces, a lubrication mechanism for 2D/2D nanohybrid of MoS2/CeO2 was proposed. This research might promote the application of MoS2/CeO2 nanohybrid as additive for ecologically friendly lubricants.

An ultra-thin 2D-CeO2 non-carbon support for significantly improving the methanol oxidation and oxygen reduction reactions

The order-disordered CeO2 nanosheets were used as the non-carbon support of PtCu electrocatalyst for enhancing the MOR and ORR.

Ultrathin heteroatom-doped CeO2 nanosheet assemblies for durable oxygen evolution: Oxygen vacancy engineering to trigger deprotonation

The manipulation of oxygen vacancies (OVs) in metal oxides has progressively emerged as a versatile strategy for improving their catalytic performance. In this study, we aim to enhance the oxygen evolution reaction (OER) performance of cerium oxide (CeO2) by doping heteroatoms (Fe, Co, Ni) to generate additional OVs. We systematically analyzed both the morphology and electronic structure of the obtained CeO2 catalysts. The experimental results revealed the self-assembly of two-dimensional (2D) CeO2 nanosheets, with an approximate thickness of ∼1.7 nm, into 2D nanosheet assemblies (NSAs). Moreover, the incorporation of heteroatoms into the CeO2 matrix promoted the formation of OVs, resulting in a significant enhancement of the OER performance of CeO2. Among them, the Co-doped CeO2 NSAs sample displayed the highest activity and durability, with almost negligible activity loss during extended operating periods. The roles of heteroatom doping in improving OER activity were explored by DFT calculations. The produced OVs improve the adsorption of hydroxyl groups (OH−), promote the deprotonation process, and increase more active sites. These findings suggest that doping CeO2 with heteroatoms is a promising strategy for improving electrocatalytic OER activity, with great potential for the development of clean energy technologies, including but not limited to water splitting and fuel cells.

Engineering of Micro-mesoporous two-dimensional CeO2-based heterojunction oxides for energy storage applications

With growing demands on energy supply and storage, there is a need for advanced devices that can meet the high power and energy requirements. One such device is a supercapacitor, which is classified into two types, namely the electrical double-layer capacitor (EDLC) and the pseudocapacitor. Pseudocapacitors show energy storage properties that are between EDLCs and batteries and generally, transition metal oxides are used for these applications. Recent work has demonstrated that CeO2 is a potential material for such applications owing to its reversible charge-switching capabilities and good stability in different environments. In the present work, novel ultrathin nanosheets of CeO2-x and a composite of ruthenium (Ru)-CeO2-x, with the Ru in the form of mixed heteroatoms and dopants were synthesised using a Ce-based coordination polymer (Ce-CP) as the precursor using modified anodic chronoamperometric electrodeposition (MACE) technique. The ready exfoliation of Ce-CP in triethanolamine, which was the exfoliation medium, followed by solvent removal and annealing at 300 °C resulted in the formation of ultrathin 2D CeO2 nanosheets that are partially stacked, resulting in the formation of flower-like 3D nanostructures. The ultrathin 2D CeO2 formed 3D flower-like nanostructures with high concentrations of defects, active sites, and mesopores, which increased with the concentration of Ru in the CeO2-x nanostructure. Additionally, the specific surface area of the Ru-CeO2-x samples was higher, increasing to 354 m2·g−1 compared to the value of 146 m2·g−1 for pristine CeO2-x. The cyclic voltammetry analysis revealed that the introduction of Ru increased the capacitance of pristine CeO2-x from 665 F·g−1 to 923 F·g−1 at a scan rate of 5 mV·s−1. These findings suggest that Ru-CeO2-x nanosheets have potential for use in supercapacitor applications.

Photocatalytic degradation efficiencies of ZnO nanoparticles and CeO2 nanosheets synthesized via combustion method

Photocatalytic degradation efficiencies of ZnO nanoparticles and CeO2 nanosheets synthesized via combustion method

Polarized Active Pairs at Grain Boundary Boost CO2 Chemical Fixation.

The chemical fixation of CO2 as a C1 feedstock is considered one of the most promising ways to obtain long-chain chemicals, but its efficiency was limited by the ineffective activation of CO2. Herein, we propose a grain boundary engineering strategy to construct polarized active pairs with electron poor-rich character for effective CO2 activation. By taking CeO2 as a model system, we illustrate that the polarized "Ce4+-Ce3+-Ce4+" pairs at the grain boundary can simultaneously accept and donate electrons to coordinate with O and C, respectively, in CO2. By the combination of synchrotron radiation in situ technique and density functional theory calculations, the mechanism of the catalytic reaction has been systematically investigated. As a result, the CeO2 nanosheets with a rich grain boundary show a high DMC yield of 60.3 mmol/gcat with 100% atomic economy. This study provides a practical way for the chemical fixation of CO2 to high-value-added chemicals via grain boundary engineering.

Ti doped CeO2 nanosheets supported Pd catalyst for alcohol oxidation: Catalysis of interfacial sites

AbstractThe oxidation of alcohols is a significant chemical reaction, and the efficient oxidation of alcohols over heterogeneous catalysts using oxygen as oxidant has attracted much attention in recent years. Among them, Pd/CeO2 exhibits excellent alcohol oxidation performance. However, the structure-activity relationship between the catalyst's structure and its catalytic performance for alcohol oxidation is still not clearly understood. This study involved the preparation of CeO2 nanosheets with different concentrations of surface oxygen vacancies (Ov) and their subsequent loading with Pd to explore their catalytic performance for alcohol oxidation. The findings obtained through XPS, Raman, and XAS indicated a positive correlation between the surface Ov concentration of CeO2 as well as the ratio of Pd2+ fraction. The alcohol oxidation results and structure-performance relationship studies showed that there was a good linear relationship between the Pd2+ ratio as well as the surface Ce3+ concentration and the TOF of benzyl alcohol oxidation reaction, respectively. And the interfacial site (Pd–O–Ce) formed by Pd and CeO2 was the main catalytic site for this type of alcohol oxidation catalysts. This study contributes to the understanding of the catalytic role of interfacial sites in metal and oxide support for the development of better alcohol oxidation catalysts.

Construction of 2D/2D Mesoporous WO3/CeO2 Laminated Heterojunctions for Optimized Photocatalytic Performance.

Photocatalytic elimination of antibiotics from the environment and drinking water is of great significance for human health. However, the efficiency of photoremoval of antibiotics such as tetracycline is severely limited by the prompt recombination of electron holes and slow charge migration efficacy. Fabrication of low-dimensional heterojunction composites is an efficient method for shortening charge carrier migration distance and enhancing charge transfer efficiency. Herein, 2D/2D mesoporous WO3/CeO2 laminated Z-scheme heterojunctions were successfully prepared using a two-step hydrothermal process. The mesoporous structure of the composites was proved by nitrogen sorption isotherms, in which sorption-desorption hysteresis was observed. The intimate contact and charge transfer mechanism between WO3 nanoplates and CeO2 nanosheets was investigated using high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy measurements, respectively. Photocatalytic tetracycline degradation efficiency was noticeably promoted by the formation of 2D/2D laminated heterojunctions. The improved photocatalytic activity could be attributed to the formation of Z-scheme laminated heterostructure and 2D morphology favoring spatial charge separation, confirmed by various characterizations. The optimized 5WO3/CeO2 (5 wt.% WO3) composites can degrade more than 99% of tetracycline in 80 min, achieving a peak TC photodegradation efficiency of 0.0482 min-1, which is approximately 3.4 times that of pristine CeO2. A Z-scheme mechanism is proposed for photocatalytic tetracycline by from WO3/CeO2 Z-scheme laminated heterojunctions based on the experimental results.

Rationally Designed CeO2 Nanosheets over Co9S8 Nanoparticles form S‐Scheme Heterojunction for Efficient Hydrogen Production

AbstractEnriching the active sites of catalysts and artificially regulating the directional migration of photogenerated carriers are effective means to improve the catalytic activity of photocatalysts. In this work, CeO2 nanosheets are prepared by calcination at high temperatures, and the S‐scheme heterojunction photocatalyst CeO2@Co9S8 is prepared by coupling the Co9S8 nanoparticles prepared by hydrothermal method on CeO2 nanosheets. The large specific surface area of CeO2 nanosheets provides sufficient loading sites for Co9S8 and Co9S8 nanoparticles can effectively disperse with the help of CeO2 nanosheet structure, which effectively inhibits the agglomeration of nanoparticles. The high photosensitivity of Co9S8 increases the utilization of CeO2@Co9S8 S‐scheme heterojunction to visible light. The construction of S‐scheme heterojunction improves the separation efficiency of photogenerated carriers, prolongs the service life of photogenerated charges, retains the photogenerated electrons and holes with strong reduction and oxidation ability in the catalyst system, and improves the performance of photocatalytic hydrogen production. The hydrogen yield of 15 wt% Co9S8 supported CeO2@Co9S8 can reach 15.7 times CeO2 and 2.5 times Co9S8, and the composite catalyst has good stability. This work provides a new way for adjusting the surface structure and carrier behavior of photocatalysts.

Improved NH3-SCR activity by the cooperation of FeVO4 and CeO2 nanosheet catalysts: structure and mechanism

The cooperation of FeVO4 and CeO2 nanosheets significantly improves NH3-SCR activity via the nanosheet structure with lattice defects and Fe–V–Ce interaction.

Atomic strategy to boost the solar heating ammonia decomposition of cobalt-based catalyst

Solar heating catalysis can solve the massively fossil energy consumption of ammonia decomposition to produce carbon-free hydrogen energy. Efficient and non-noble catalysts have always been the pursuit in solar heating ammonia decomposition. Herein, Co single atoms supported on CeO2 nanosheets (SA Co/CeO2) are synthesized and show the 29.1 mmol g−1 min−1 of H2 production rate from ammonia decomposition at 450 °C, which is 291 times higher than the corresponding Co nanoparticles and equivalent to the noble metal catalysts. Theoretical calculations illustrate that the SA Co/CeO2 can effectively reduce the energy barrier of nitrogen binding in ammonia decomposition, beneficial to the progress of ammonia decomposition reaction. The SA Co/CeO2 makes solar heating ammonia decomposition exhibit a stable H2 generation rate of 2.7 mmol g−1 min−1 under 2 suns irradiation, 572 times higher than the weak sunlight-driven ammonia decomposition, and the produced hydrogen can direct drive hydrogen fuel cell without any purification. This discovery not only opens a new route to develop ultra-active catalysts for ammonia decomposition but also demonstrates the potential of solar driven hydrogen fuel cell.

Photocatalytic activity and mechanism of cerium dioxide with different morphologies for tetracycline degradation

Cerium dioxide (CeO2) semiconductor has received wide attention in the field of energy and environment due to its excellent oxygen storage capacity and abundant oxygen vacancies (OVs). Previous research demonstrated that the morphology and structure of the crystal had great influence on the physicochemical properties of the material. Herein, CeO2 nanomaterials with different morphologies were prepared via a facile hydrothermal and template method. Systematic material characterizations suggested that the synthetic CeO2 has different morphologies with CeO2 nanorods (NRs), nanocubes (NCs), nanosheets (NSs), hollow spheres (HSs), and mesoporous CeO2 (m-CeO2), respectively. The visible-light-induced degradation performance of CeO2 with different morphologies was investigated in aqueous solution using the antibiotic tetracycline (TC) as a model pollutant. The experimental results exhibited that the CeO2NRs possessed the best adsorption capacity and photocatalytic activity and more than 89.35% TC could be removed within 90 min. Combined with the XPS characterization results implied that the concentrations of Ce3+ and OVs on the surface of CeO2 with different morphologies were discrepancy, and the improved photocatalytic performance of CeO2NRs was mainly due to the higher concentration of Ce3+ and OVs on the catalyst surface. These results confirmed that the regulation of the morphology of CeO2 could effectively enhance its photocatalytic activity. Furthermore, the results of active species trapping experiments proved that the super oxide anion (•O2-) radical and hole (h+) played dominant roles in the degradation of TC.