The rational design of sandwich-like MnO2-Pd-CeO2 hollow spheres with enhanced activity and stability for CO oxidation

Low Temperature NO and CO Conversion with a Mechanistic Approach on Ru-Composed Cerium Oxide

Catalytic reduction of NO with CO at a lower temperature is an extremely challenging task, thus requiring conceivable surfaces to overcome such issues. Ru-substituted CeO2 catalysts prepared via the solution combustion method were employed in CO oxidation and NO-CO conversion studies. The characterization for material formation and surface structure was carried out through XRD, SEM, TEM, and BET surface area. The catalytic study revealed the promising behavior of 5% Ru in CeO2 for the 100% conversion of NO-CO at 150 °C, proving it to be an excellent exhaust material. These observed results are also supported by temperature-programmed studies, i.e. TPD of NO and CO in addition to NH3-TPD and H2-TPR for their convincible surface interaction that is inclined toward a significant change in the conversion path. Additionally, the proposed mechanism, based on the experimental evidence, sheds light on the NO-CO redox reaction, directing the reaction pathway toward the Langmuir-Hinshelwood and Mars-Van Krevelen-type route. Moreover, the exceptional performance can be attributed to the strategic incorporation of Ru in CeO2, where the strong interaction of Ru-Ce is able to gain a high synergy for NO and CO conversion.

The Structures and Compositions Design of the Hollow Micro-Nano-Structured Metal Oxides for Environmental Catalysis

In recent decades, with the rapid development of the inorganic synthesis and the increasing discharge of pollutants in the process of industrialization, hollow-structured metal oxides (HSMOs) have taken on a striking role in the field of environmental catalysis. This is all due to their unique structural characteristics compared to solid nanoparticles, such as high loading capacity, superior pore permeability, high specific surface area, abundant inner void space, and low density. Although the HSMOs with different morphologies have been reviewed and prospected in the aspect of synthesis strategies and potential applications, there has been no systematic review focusing on the structures and compositions design of HSMOs in the field of environmental catalysis so far. Therefore, this review will mainly focus on the component dependence and controllable structure of HSMOs in the catalytic elimination of different environmental pollutants, including the automobile and stationary source emissions, volatile organic compounds, greenhouse gases, ozone-depleting substances, and other potential pollutants. Moreover, we comprehensively reviewed the applications of the catalysts with hollow structure that are mainly composed of metal oxides such as CeO2, MnOx, CuOx, Co3O4, ZrO2, ZnO, Al3O4, In2O3, NiO, and Fe3O4 in automobile and stationary source emission control, volatile organic compounds emission control, and the conversion of greenhouse gases and ozone-depleting substances. The structure-activity relationship is also briefly discussed. Finally, further challenges and development trends of HSMO catalysts in environmental catalysis are also prospected.

In Situ Reconstruction of Active Heterointerface for Hydrocarbon Combustion through Thermal Aging over Strontium-Modified Co3O4 Nanocatalyst with Good Sintering Resistance

The issue of catalyst deactivation due to sintering has gained significant attention alongside the rapid advancement of thermal catalysts. In this work, a simple Sr modification strategy was applied to achieve highly active Co3O4-based nanocatalyst for catalytic combustion of hydrocarbons with excellent antisintering feature. With the Co1Sr0.3 catalyst achieving a 90% propane conversion temperature (T90) of only 289 °C at a w8 hly space velocity of 60,000 mL·g-1·h-1, 24 °C lower than that of pure Co3O4. Moreover, the sintering resistance of Co3O4 catalysts was greatly improved by SrCO3 modification, and the T90 over Co1Sr0.3 just increased from 289 to 337 °C after thermal aging at 750 °C for 100 h, while that over pure Co3O4 catalysts increased from 313 to 412 °C. Through strontium modification, a certain amount of SrCO3 was introduced on the Co3O4 catalyst, which can serve as a physical barrier during the thermal aging process and further formation of Sr-Co perovskite nanocrystals, thus preventing the aggregation growth of Co3O4 nanocrystals and generating new active SrCoO2.52-Co3O4 heterointerface. In addition, propane durability tests of the Co1Sr0.3 catalysts showed strong water vapor resistance and stability, as well as excellent low-temperature activity and resistance to sintering in the oxidation reactions of other typical hydrocarbons such as toluene and propylene. This study provides a general strategy for achieving thermal catalysts by perfectly combining both highly low-temperature activity and sintering resistance, which will have great significance in practical applications for replacing precious materials with comparative features.

Nanotraps based on multifunctional materials for trapping and enrichment

Many biomarkers for early diagnosis of cancer and other diseases are difficult to detect because they often exist in body fluids in very low concentrations and are masked by high-abundance proteins such as albumin and immunoglobulins. At the same time, water pollution is one of the most serious environmental problems, but the existing adsorption materials have many shortcomings such as slow kinetics, small adsorption capacity and low adsorption efficiency. Nanotraps, mixed with gases or liquids, can capture and concentrate target substances, such as biomolecules, metal ions and oxoanions. Using nanotraps is a versatile sample pre-processing approach and it can improve the sensitivity of downstream analysis techniques. Herein, the preparations and applications of different types of nanotraps are mainly introduced. What's more, the shortcomings of using nanotraps in practical applications are also discussed. Using nanotraps is a promising sample pre-processing technology, which is of great significance for biomarkers discovery, diseases diagnosis, sewage purification and valuable ions recovery. STATEMENT OF SIGNIFICANCE: This review collates and summarizes the preparations and applications of different types of nanotraps, and discusses the shortcomings of using nanotraps in practical applications. Nanotraps, mixed with gases or liquids, can capture and concentrate target materials, such as biomolecules, metal ions and oxoanions. Using nanotraps is a versatile sample pre-processing approach and it can improve the sensitivity of downstream analysis techniques. During the COVID-19 pandemic, hydrogel nanotraps were successfully utilized for RT-PCR analysis with the FDA Emergency Used Authorization for COVID-19. Using nanotraps is a promising sample pre-processing technology, which is of great significance for biomarkers discovery, diseases diagnosis, sewage purification and valuable ions recovery.

“Three-in-One” Nanocomposite as Multifunctional Nanozyme for Ultrasensitive Ratiometric Fluorescence Detection of Alkaline Phosphatase

Nanozymes, as a unique class of nanomaterials with enzyme-like properties, have attracted significant interests due to their potential applications in many significant fields. Great endeavours have been devoted to improving...

MnO2 -Based Materials for Environmental Applications

Manganese dioxide (MnO₂ ) is a promising photo-thermo-electric-responsive semiconductor material for environmental applications, owing to its various favorable properties. However, the unsatisfactory environmental purification efficiency of this material has limited its further applications. Fortunately, in the last few years, significant efforts have been undertaken for improving the environmental purification efficiency of this material and understanding its underlying mechanism. Here, the aim is to summarize the recent experimental and computational research progress in the modification of MnO₂ single species by morphology control, structure construction, facet engineering, and element doping. Moreover, the design and fabrication of MnO₂ -based composites via the construction of homojunctions and MnO₂ /semiconductor/conductor binary/ternary heterojunctions is discussed. Their applications in environmental purification systems, either as an adsorbent material for removing heavy metals, dyes, and microwave (MW) pollution, or as a thermal catalyst, photocatalyst, and electrocatalyst for the degradation of pollutants (water and gas, organic and inorganic) are also highlighted. Finally, the research gaps are summarized and a perspective on the challenges and the direction of future research in nanostructured MnO₂ -based materials in the field of environmental applications is presented. Therefore, basic guidance for rational design and fabrication of high-efficiency MnO₂ -based materials for comprehensive environmental applications is provided.

Ce-Mn coordination polymer derived hierarchical/porous structured CeO2-MnOx for enhanced catalytic properties

Catalytic performance is largely dependent on how the structures/compositions of materials are designed. Herein, CeO2-MnOx binary oxide catalysts with a hierarchical/porous structure are prepared by a facile and efficient method, which involves the preparation of the hierarchical Ce-Mn coordination polymer (CPs) precursor, followed by a thermal treatment step. The obtained CeO2-MnOx catalysts not only well inherit the hierarchical structure of Ce-Mn CPs, but also possess porous and hollow features due to the removal of organic ligands and heterogeneous contraction during the calcination process. In addition, the effect of the Mn/Ce ratio is also studied to optimize catalytic performance. Specifically, the as-prepared CeO2-MnOx (5 : 5) catalyst exhibits excellent catalytic performance toward CO oxidation and selective catalytic reduction (SCR) of NO with NH3 at low temperatures. Based on the characterization results, we propose that the special hierarchical structure, high surface area, strong synergistic interaction between CeO2 and MnOx, and high content of active Ce3+, Mn4+ and Osurf are collectively responsible for its remarkable catalytic performance.

Rare Earth Oxide Anchored Platinum Catalytic Site Coated Zeolitic Imidazolate Frameworks toward Enhancing Selective Hydrogenation

Controlling and manipulating the self-assembly technology at the nanoscale has become a powerful strategy for improving chemical processes and further developing the conception of atom efficiency. Herein, an unexpected core-shell structured Gd₂O₃@Pt@ZIF-8 nanoreactor has been fabricated using the self-assembly strategy in which the firm Gd₂O₃ nanosupport anchored the highly active Pt nanoparticle coated porous zeolitic imidazolate framework (ZIF-8). The well-designed Gd₂O₃@Pt@ZIF-8 structure shows good performance in selective hydrogenation of aldehyde-, keto-, and nitro-compounds with full conversion (>99.9%) and superior selectivity (>95%). It showed the channel sieving effect of the ZIF-8 channels toward enhancing the catalytic selectivity. After being recycled eight times, their activity remains unchanged and their core-shell structure is kept intact. So, the outer ZIF-8 membranes not only prevent Pt nanoparticles from agglomeration and slipping during a catalytic reaction but also maintain the original activity and long-term stability compared to the Gd₂O₃@Pt catalyst. The self-assembly strategy demonstrated here will allow the development of other highly active, stable, and selective catalysts for important but challenging transformations.

The contributions of distinct Pd surface sites in palladium–ceria catalysts to low-temperature CO oxidation

The low-temperature CO oxidation properties of Pd/CeO₂ catalysts can be correlated with the distribution of PdO_x/Pd–O–Ce species.