Pressure Regulations on the Surface Properties of CeO2 Nanorods and Their Catalytic Activity for CO Oxidation and Nitrile Hydrolysis Reactions

Resistant starch grafted cerium-sulfasalazine infinite coordination polymers synergistically remold intestinal metabolic microenvironment for inflammatory bowel disease therapy

Inflammatory bowel disease (IBD) is a chronic gastrointestinal disease which is closely related with the overproduced reactive oxygen species (ROS), increased pro-inflammatory cytokines and disordered intestinal microbes. However, current therapeutic methods usually ignored the interrelation among the pathogenesis, and mainly focused on a single factor, inducing clinical outcomes unsatisfied. Herein, biocompatible infinite coordination polymers of drugs (Ce-SASP-RS ICPs) composed of Ce ions, FDA-approved drug sulfasalazine (SASP) and natural ingredient resistant starch (RS) were developed for synergistic treatment of IBD. The proper Ce3+/Ce4+ ratio in Ce-SASP-RS ICPs can endow them with SOD-like activities, POD-like activities and •OH scavenging ability, which guarantee Ce-SASP-RS ICPs to simultaneously kill bacteria and maintain ROS balance through cascade reactions. Owing to the recovered redox balance microenvironment, SASP in Ce-SASP-RS ICPs can better play their anti-inflammatory function. Moreover, benefitting from the recovered metabolic balance of ROS and inflammatory cytokines in colon, resistant starch can also function better in modifying gut microbiota through generating short-chain fatty acids. Collectively, Ce-SASP-RS ICPs can synergistically restore intestinal metabolic microenvironment through modulating redox balance, attenuating inflammation and modifying intestinal flora. Hence, in view of the mutual influences among IBD pathogenesis, this work presents a synergistic intervention approach for effectively treating IBD.

Ce-based three-dimensional mesoporous microspheres with Mn homogeneous incorporation for toluene oxidation

Ce-based three-dimensional (3D) mesoporous microspheres with Mn homogeneous incorporation were synthesized. The CeMn-0.4, characterized by a Ce/Mn molar ratio of 6:4, demonstrated exceptional catalytic activity and stability. The formation of CeMn solid solution strengthened the Ce-Mn interaction, yielding higher concentrations of Ce3+ and Mn4+. Mn4+ initiated toluene preliminary activation owing to its robust oxidative properties, while Ce3+ contributed to oxygen vacancy generation, enhancing the activation of gaseous oxygen and lattice oxygen mobility. Integrating experiments and Density Functional Theory (DFT) calculations elucidated the oxygen reaction mechanisms. A portion of oxygen was converted into surface reactive oxygen species (Oads) that directly oxidized toluene. Additionally, the presence of oxygen vacancies promoted the participation of oxygen in toluene oxidation by converting it into lattice oxygen, which was crucial for the deep oxidation of toluene. Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS) indicated the accumulation of benzene-ring intermediates on the catalyst surface hindered continuous toluene oxidation. Thus, the abundant oxygen vacancies in CeMn-0.4 played a pivotal role in sustaining the oxidation process by bolstering the activation of gaseous oxygen and the mobility of lattice oxygen.

Demonstration of a Gel-Polymer Electrolyte-Based Electrochromic Device Outperforming Its Solution-Type Counterpart in All Merits: Architectural Benefits of CeO2 Quantum Dot and Nanorods

For years, solution-type electrochromic devices (ECDs) have intrigued researchers' interest and eventually rendered themselves into commercialization. Regrettably, challenges such as electrolyte leakage, high flammability, and complicated edge-encapsulation processes limit their practical utilization, hence necessitating an efficient alternate. In this quest, although the concept of solid/gel-polymer electrolyte (SPE/GPE)-based ECDs settled some issues of solution-type ECDs, an array of problems like high operating voltage, sluggish response time, and poor cycling stability have paralyzed their commercial applicability. Herein, we demonstrate a choreographed-CeO2-nanofiller-doped GPE-based ECD outperforming its solution-type counterpart in all merits. The filler-incorporated polymer electrolyte assembly was meticulously weaved through the electrospinning method, and the resultant host was employed for immobilizing electrochromic viologen species. The filler engineering benefits conceived through the tuned shape of CeO2 nanorod and quantum dots, along with the excellent redox shuttling effect of Ce3+/Ce4+, synchronously yielded an outstanding class of GPE, which upon utilization in ECDs delivered impressive electrochromic properties. A combination of features possessed by a particular device (QD-NR/PVDF-HFP/IL/BzV-Fc ECD) such as exceptionally low driving voltage (0.9 V), high transmittance change (ΔT, ∼69%), fast response time (∼1.8 s), high coloration efficiency (∼339 cm2/C), and remarkable cycling stability (∼90% ΔT-retention after 25,000 cycles) showcased a striking potential in the yet-to-realize market of GPE-based ECDs. This study unveils the untapped potential of choreographed nanofillers that can promisingly drive GPE-based ECDs to the doorstep of commercialization.

Catalysts Prepared from Atomically Dispersed Ce(III) on MgO Rival Bulk Ceria for CO Oxidation

Atomically dispersed cerium catalysts on an inert, crystalline MgO powder support were prepared by using both Ce(III) and Ce(IV) precursors. The materials were used as catalysts for CO oxidation in a once-through flow reactor and characterized by atomic-resolution scanning transmission electron microscopy, X-ray absorption near-edge structure spectroscopy, X-ray photoelectron spectroscopy, and temperature-programmed reduction, among other techniques, before and after catalysis. The most active catalysts, formed from the precursor incorporating Ce(III), displayed performance similar to that reported for bulk ceria under comparable conditions. The catalyst provided stable time-on-stream performance for as long as it was kept on-stream, 2 days, increasing slightly in activity as the atomically dispersed cerium ions were transformed into ceria nanodomains represented as CeOx and having increased reducibility on the MgO support. The results suggest how highly dispersed supported ceria catalysts with low cerium loadings can be prepared and may pave the way for improved efficiencies of cerium utilization in oxidation catalysis.

Ultrasonically assisted surface modified CeO2 nanospindle catalysts for conversion of CO2 and methanol to DMC

This study developed a facile and effective approach to engineer the surface properties of cerium oxide (CeO2) nanospindle catalysts for the direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol. CeO2 nanospindles were first prepared by a simple precipitation method followed by wet chemical redox etching with sodium borohydride (NaBH4) under high intensity ultrasonication (ultrasonic horn, 20 kHz, 150 W/cm2). The ultrasonically assisted surface modification of the CeO2 nanospindles in NaBH4 led to particle collisions and surface reduction that resulted in an increase in the number of surface-active sites of exposed Ce3+ and oxygen vacancies. The surface modified CeO2 nanospindles showed an improvement of catalytic activity for DMC formation, yielding 17.90 mmol·gcat-1 with 100 % DMC selectivity. This study offers a simple and effective method to modify a CeO2 surface, and it can further be applied for other chemical activities.

Cerium-terephthalic acid metal-organic frameworks for ratiometric fluorescence detecting and scavenging·OH from fuel combustion gas

Hydroxyl radical (•OH) in fuel combustion gas seriously damages human health. The techniques for simultaneously detecting and scavenging •OH in these gases are limited by poor thermal resistance. To meet this challenge, herein, metal organic frameworks (MOFs) with high thermal stability (80-400 °C) and dual function (•OH detection and elimination) are developed by coordinating Ce ions with terephthalic acid (TA) (Ce-BDC). Due to the reversible conversion between Ce³⁺ and Ce⁴⁺, and the high concentration of Ce³⁺ on the surface of Ce-BDC MOFs (89.6%), an •OH scavenging efficiency over 90% is realized. Ratiometric fluorescence (I_440 nm/I_355 nm) detection of •OH with a low detection limit of ∼4 μM is established by adopting Ce ions as an internal standard and TA as an •OH-responsive fluorophore. For real applications, the Ce-BDC MOFs demonstrate excellent •OH detection sensitivity and high •OH scavenging efficiency in gas produced from cigarettes, wood fiber and machine oil. Mouse model results show that the damage caused by •OH in cigarette smoke can be greatly reduced by Ce-BDC MOFs. This work provides a promising strategy for sensitively detecting and efficiently eliminating •OH in fuel combustion gas.

Enhanced catalytic performance of atomically dispersed Pd on Pr-doped CeO2 nanorod in CO oxidation

Single-atom noble metal catalysts have been widely studied for catalytic oxidation of CO. Regulating the coordination environment of single metal atom site is an effective strategy to improve the intrinsic catalytic activity of single atom catalyst. In this work, single atom Pd catalyst supported on Pr-doped CeO₂ nanorods was prepared, and the performance and nature of Pr-coordinated atomic Pd site in CO catalytic oxidation are systematically investigated. The structure characterization using AC-HAADF-STEM, EXAFS, XRD and Raman spectroscopy demonstrate the formation of single atom Pd site and abundant surface oxygen vacancies on the surface of Pr-doped CeO₂ nanorod. With the combination of the XPS characterization and DFT calculations, the oxidation state of Pd on Pr-doped CeO₂ nanorod is determined lower than that on CeO₂ nanorod. The turnover frequency of CO oxidation is markedly increased from 8.4 × 10^-3 to 31.9 × 10^-3 s with Pr-doping at 130 ºC and GHSV of 70,000 h^-1. Combined with kinetic studies, DRIFT and DFT calculations, the doped-Pr atoms reduced the formation energy of oxygen vacancies and generate more oxygen vacancies around the atomically dispersed Pd sites on the surface of cerium oxide, which reduces the dissociation energy of oxygen, thereby accelerating the reaction rate of CO oxidation.

Insights on catalytic mechanism of CeO2 as multiple nanozymes

CeO₂ with the reversible Ce³⁺/Ce⁴⁺ redox pair exhibits multiple enzyme-like catalytic performance, which has been recognized as a promising nanozyme with potentials for disease diagnosis and treatments. Tailorable surface physicochemical properties of various CeO₂ catalysts with controllable sizes, morphologies, and surface states enable a rich surface chemistry for their interactions with various molecules and species, thus delivering a wide variety of catalytic behaviors under different conditions. Despite the significant progress made in developing CeO₂-based nanozymes and their explorations for practical applications, their catalytic activity and specificity are still uncompetitive to their counterparts of natural enzymes under physiological environments. With the attempt to provide the insights on the rational design of highly performed CeO₂ nanozymes, this review focuses on the recent explorations on the catalytic mechanisms of CeO₂ with multiple enzyme-like performance. Given the detailed discussion and proposed perspectives, we hope this review can raise more interest and stimulate more efforts on this multi-disciplinary field.

Al2O3-Coated Ni/CeO2 nanoparticles as coke-resistant catalyst for dry reforming of methane

To mitigate catalyst deactivation during the dry reforming of methane, Ni/CeO₂ catalysts composed of monodisperse Ni nanoparticles supported on CeO₂ nanorods are designed and coated with Al₂O₃ layers by atomic layer deposition.

Engineering CuOx–ZrO2–CeO2 nanocatalysts with abundant surface Cu species and oxygen vacancies toward high catalytic performance in CO oxidation and 4-nitrophenol reduction

CuO_x–ZrO₂–CeO₂ nanocrystalline catalysts were designed and synthesized by a solvent-free synthetic strategy, and exhibited excellent catalytic performance owing to the increased oxygen vacancies and better dispersed active metal species.

The solid-state in situ construction of Cu2O/CuO heterostructures with adjustable phase compositions to promote CO oxidation activity

Cu₂O/CuO heterojunctions were fabricated via in situ solid-state technology. Tuning the ratio of reactants enables optimization of the components of the Cu₂O/CuO heterostructures and their catalytic activities for CO oxidation.

Sub-15 nm CeO2 nanowires as an efficient non-noble metal catalyst in the room-temperature oxidation of aniline

We described the facile synthesis of sub-15 nm CeO₂ nanowires for catalyzing the selective synthesis of nitrosobenzene from aniline at room temperature.

New Routes for Refinery of Biogenic Platform Chemicals Catalyzed by Cerium Oxide-supported Ruthenium Nanoparticles in Water

Highly selective hydrogenative carbon-carbon bond scission of biomass-derived platform oxygenates was achieved with a cerium oxide-supported ruthenium nanoparticle catalyst in water. The present catalyst enabled the selective cleavage of carbon-carbon σ bonds adjacent to carboxyl, ester, and hydroxymethyl groups, opening new eight synthetic routes to valuable chemicals from biomass derivatives. The high selectivity for such carbon-carbon bond scission over carbon-oxygen bonds was attributed to the multiple catalytic roles of the Ru nanoparticles assisted by the in situ formed Ce(OH)₃.

2D NiFe/CeO2 Basic-Site-Enhanced Catalyst via in-Situ Topotactic Reduction for Selectively Catalyzing the H2 Generation from N2H4·H2O

An economical catalyst with excellent selectivity and high activity is eagerly desirable for H₂ generation from the decomposition of N₂H₄·H₂O. Here, a bifunctional two-dimensional NiFe/CeO₂ nanocatalyst with NiFe nanoparticles (∼5 nm) uniformly anchored on CeO₂ nanosheets supports has been successfully synthesized through a dynamic controlling coprecipitation process followed by in-situ topotactic reduction. Even without NaOH as catalyst promoter, as-designed Ni_0.6Fe_0.4/CeO₂ nanocatalyst can show high activity for selectively catalyzing H₂ generation (reaction rate (mol_N2H4 mol^-1_NiFe h^-1): 5.73 h^-1). As ceria is easily reducible from CeO₂ to CeO_2-x, the surface of CeO₂ could supply an extremely large amount of Ce³⁺, and the high-density electrons of Ce³⁺ can work as Lewis base to facilitate the absorption of N₂H₄, which can weaken the N-H bond and promote NiFe active centers to break the N-H bond preferentially, resulting in the high catalytic selectivity (over 99%) and activity for the H₂ generation from N₂H₄·H₂O.

Aerosol-Sprayed Gold/Ceria Photocatalyst with Superior Plasmonic Hot Electron-Enabled Visible-Light Activity

Integration of nanoscale plasmonic metals with semiconductors is a promising strategy for utilizing visible and near-infrared light to enhance chemical reactions. Here we report on the preparation of Au/CeO₂ microsphere photocatalysts through aerosol spray and the study of their photocatalytic activity toward the aerobic oxidation of 1-phenylethanol under visible light. The microsphere catalysts exhibit a remarkable photocatalytic performance with their turnover frequency values reaching 108 h^-1, which is more than 23 times that of (Au core)@(CeO₂ shell) nanostructures and much larger than those obtained previously for the visible-light photocatalytic oxidation of 1-phenylethanol. In addition, the Au/CeO₂ catalyst shows the best performance among eight types of oxide semiconductor supports. Moreover, the photocatalytic mechanism of the Au/CeO₂ catalyst is systematically investigated. This study offers insights for plasmonic hot electron-enabled photocatalysis, which will be valuable for the design of various efficient (plasmonic metal)/semiconductor photocatalysts.