Syntheses and Applications of Noble-Metal-free CeO2-Based Mixed-Oxide Nanocatalysts

Electron regulation of CeO2 on CoP multi-shell hetero-junction micro-sphere towards highly efficient water oxidation

CeO2 has been identified as a significant cocatalyst to enhance the electrocatalytic activity of transition metal phosphides (TMPs). However, the electrocatalytic mechanism by which CeO2 enhances the catalytic activity of TMP remains unclear. In this study, we have successfully developed a unique CeO2-CoP-1-4 multishell microsphere heterostructure catalyst through a simple hydrothermal and calcination process. CeO2-CoP-1-4 exhibits great potential for electrocatalytic oxygen evolution reaction (OER), requiring only an overpotential of 254 mV to achieve a current density of 10 mA cm-2. Moreover, CeO2-CoP-1-4 demonstrates excellent operating durability lasting for 55 h. The presence of CeO2 as a cocatalyst can regulate the microsphere structure of CoP, the resulting multishell microsphere structure can shorten the mass transfer distance, and improve the utilization rate of the active site. Furthermore, in situ Raman and ex situ characterizations, and DFT theoretical calculation results reveal that CeO2 can effectively regulates the electronic structure of Co species, reduces the reaction free energy of rate-limiting step, thus increase the reaction kinetic. Overall, this study provides experimental and theoretical evidence to better comprehend the mechanism and structure evolution of CeO2 in enhancing the OER performance of CoP, offering a unique design inspiration for the development of efficient hollow heterojunction electrocatalysts.

Interface reconstruction of MXene-Ti3C2 doped CeO2 nanorods for remarked photocatalytic ammonia synthesis

Prospective photocatalytic ammonia synthesis process has received more attentions but quite challenging with the low visible light utilization and weak N2 molecule absorption ability around the photocatalysts. Herein, interface reconstruction of MXene-Ti3C2/CeO2 composites with high-concentration active sites through the carbon-doped process are presented firstly, and obvious transition zones with the three-phase reaction interface are formed in the as-prepared catalysts. The optimal co-doped sample demonstrates an excellent photo response in the visible light region, the strongest chemisorption activity and the most active sites. Moreover, much more in-situ extra oxygen defects are also produced under light irradiation. It is expected that the double decorated catalyst shows a remarked ammonia production rate of above 0.76 mmol gcal-1·h-1 under visible-light illumination and a higher apparent quantum efficiency of 1.08 % at 420 nm, which is one of the most completive properties for the photocatalytic N2 fixation at present.

New trends in nanoparticle exsolution

Many relevant high-temperature chemical processes require the use of oxide-supported metallic nanocatalysts. The harsh conditions under which these processes operate can trigger catalyst degradation via nanoparticle sintering, carbon depositions or poisoning, among others. This primarily affects metallic nanoparticles created via deposition methods with low metal-support interaction. In this respect, nanoparticle exsolution has emerged as a promising method for fabricating oxide-supported nanocatalysts with high interaction between the metal and the oxide support. This is due to the mechanism involved in nanoparticle exsolution, which is based on the migration of metal cations in the oxide support to its surface, where they nucleate and grow as metallic nanoparticles partially embedded in the oxide. This anchorage confers high robustness against sintering or coking-related problems. For these reasons, exsolution has attracted great interest in the last few years. Multiple works have been devoted to proving the high catalytic stability of exsolved metallic nanoparticles in several applications for high-temperature energy storage and conversion. Additionally, considerable attention has been directed towards understanding the underlying mechanism of metallic nanoparticle exsolution. However, this growing field has not been limited to these types of studies and recent discoveries at the forefront of materials design have opened new research avenues. In this work, we define six new trends in nanoparticle exsolution, taking a tour through the most important advances that have been recently reported.

Investigation of bionano additives in red algae Cyanidioschyzon merolae ultrasonified MgO/MWCNT catalyzed biodiesel in optimized engine performance

Renewable energy research is burgeoning with the anticipation of finding neat liquid fuel. Ultra sonification assisted biodiesel was derived from red algae Cyanidioschyzon merolae, with BD yield of 98.9%. The results of GC MS of the prepared biodiesel showed higher concentration of methyl palmitate, methyl oleate, and stearate. This composition is appreciable, as this plays significant in desirable pour & cloud point properties. NMR spectrum revealed the ester linkages, presence of olefins, and α methyl position in olefins. Mixture of 30wt% of biodiesel in diesel exhibited work efficiency at low pour point and, lower viscosity of biodiesel was observed. CeO2 and Fe2O3 nano particles were bio reduced, and were added as nano additive in biodiesel. 1:1 ratio of CeO2 and Fe2O3 added to biodiesel maximised the oxygen storage capacity of CeO2, and improved the combustion reactions of Fe2O3. Further, this combination produced a satisfactory Calorific value. Imbalanced ratios disrupted the catalytic and oxygen storage effects, reduced the overall energy release and calorific value of the biodiesel blend. Pour point and cetane number value of A/F/C-1 was around -7 oC and 53 respectively, and was better than other compositions. 1:1 mass ratio of NPS blended with 30wt% BD in diesel showed tremendous increase in BTE, torque, and power. HC, NOX, and SOX emissions were reduced by 42.8%, 19.3%, and 57% respectively. CeO2 favourably improved the oxygen storage capacity of the fuel, whereas Fe2O3 showed decrease in formation of gums and sediments in biodiesel.

Ceria-Optimized Oxygen-Species Exchange in Hierarchical Bimetallic Hydroxide for Electrocatalytic Water Oxidation

The utilization of rare earth elements to regulate the interaction between catalysts and oxygen-containing species holds promising prospects in the field of oxygen electrocatalysis. Through structural engineering and adsorption regulation, it is possible to achieve high-performance catalytic sites with a broken activity-stability tradeoff. Herein, this work fabricates a hierarchical CeO2/NiCo hydroxide for electrocatalytic oxygen evolution reaction (OER). This material exhibits superior overpotentials and enhanced stability. Multiple potential-dependent experiments reveal that CeO2 promotes oxygen-species exchange, especially OH- ions, between catalyst and environment, thereby optimizing the redox transformation of hydroxide and the adsorption of oxygen-containing intermediates during OER. This is attributed to the reduction in the adsorption energy barrier of Ni to *OH facilitated by CeO2, particularly the near-interfacial Ni sites. The less-damaging adsorbate evolution mechanism and the CeO2 hierarchical shell significantly enhance the structural robustness, leading to exceptional stability. Additionally, the observed "self-healing" phenomenon provides further substantiation for the accelerated oxygen exchange. This work provides a neat strategy for the synthesis of ceria-based complex hollow electrocatalysts, as well as an in-depth insight into the co-catalytic role of CeO2 in terms of oxygen transfer.

Enhancing low-temperature CO removal in complex flue gases: A study on La and Cu doped Co3O4 catalysts under real-world combustion environment

Designing CO oxidation catalysts for complex flue gases conditions is particularly challenging in fire scenarios. Traditional flue gas simulations use a few representative gases but often fail to adequately evaluate catalyst performance in real-world combustion conditions. In this study, we developed doping strategies using La and Cu to enhance the water resistance of Co3O4 catalysts. Catalyst 0.1La-Co3O4-CuO/CeO2 exhibits exceptional low-temperature catalytic activity, achieving 100% conversion at 130 °C. This enhancement is largely due to the introduction of La, which increases the active Co3+/Co2+ ratio and suppresses hydroxyl group formation on the Co3O4 surface. Cu doping also changes the Co3O4 lattice structure, forming Cu+ as active sites and enhancing the activity at low temperatures. For the first time, steady-state tube furnace and fixed bed were employed to evaluate the catalytic performance of CO in actual combustion atmosphere. Catalyst 0.1La-Co3O4-CuO/CeO2 maintains excellent catalytic efficiency (T100 = 120 °C) under well-ventilated conditions. However, its activity significantly decreases in poorly ventilated environments, due to the competitive adsorption of small molecules at active sites, such as acetone, commonly found in smoke. This study provides valuable insights for designing water-resistant, low-temperature, non-noble metal catalysts and offers a methodology for evaluating CO catalytic activity in real-world environments.

Modulating band structure through introducing Cu0/CuxO composites for the improved visible light driven ammonia synthesis

The photocatalytic performance of ceria-based materials can be tuned by adjusting the surface structures with decorating the transition-metal, which are considered as the important active sites. Herein, cuprous oxide-metallic copper composite-doped ceria nanorods were assembled through a simple hydrothermal reduction method. The photocatalytic ammonia synthesis rates exhibit an inverted "V-shaped" trend with increasing Cu0/CuxO mole ratio. The best ammonia production rate, approximately 900 or 521 µmol·gcal-1·h-1 under full-spectra or visible light, can be achieved when the Cu0/CuxO ratio is approximately 0.16, and this value is 8 times greater than that of the original sample. The absorption edge of the as-prepared samples shifted towards visible wavelengths, and they also had appropriate ammonia synthesis levels. This research provides a strategy for designing noble metal-free photocatalysts through introducing the metal/metallic oxide compositesto the catalysts.

Recent Advances of CeO2-Based Composite Materials for Photocatalytic Applications

Photocatalysis has the advantages of practical, sustainable and environmental protection, so it plays a significant role in energy transformation and environmental utilization. CeO2 has attracted widespread attention for its unique 4 f electrons, rich defect structures, high oxygen storage capacity and great chemical stability. In this paper, we review the structure of CeO2 and the common methods for the preparation of CeO2-based composites in the first part. In particular, we highlight the co-precipitation method, template method, and sol-gel method methods. Then, in the second part, we introduce the application of CeO2-based composites in photocatalysis, including photocatalytic CO2 reduction, hydrogen production, degradation, selective organic reaction, and photocatalytic nitrogen fixation. In addition, we discuss several modification techniques to improve the photocatalytic performance of CeO2-based composites, such as elemental doping, defect engineering, constructing heterojunction and morphology regulation. Finally, the challenges faced by CeO2-based composites are analyzed and their development prospects are prospected. This review provides a systematic summary of the recent advance of CeO2-based composites in the field of photocatalysis, which can provide useful references for the rational design of efficient CeO2-based composite photocatalysts for sustainable development.

Constructing Built-In Electric Field in NiCo2 O4 -CeO2 Heterostructures to Regulate Li2 O2 Formation Routes at High Current Densities

Developing catalysts with suitable adsorption energy for oxygen-containing intermediates and elucidating their internal structure-performance relationships are essential for the commercialization of Li-O2 batteries (LOBs), especially under high current densities. Herein, NiCo2 O4 -CeO2 heterostructure with a spontaneous built-in electric field (BIEF) is designed and utilized as a cathode catalyst for LOBs at high current density. The driving mechanism of electron pumping/accumulation at heterointerface is studied via experiments and density functional theory (DFT) calculations, elucidating the growth mechanism of discharge products. The results show that BIEF induced by work function difference optimizes the affinity for LiO2 and promotes the formation of nano-flocculent Li2 O2 , thus improving LOBs performance at high current density. Specifically, NiCo2 O4 -CeO2 cathode exhibits a large discharge capacity (9546 mAh g-1 at 4000 mA g-1 ) and high stability (>430 cycles at 4000 mA g-1 ), which are better than the majority of previously reported metal-based catalysts. This work provides a new method for tuning the nucleation and decomposition of Li2 O2 and inspires the design of ideal catalysts for LOBs to operate at high current density.

Rare earth oxide based electrocatalysts: synthesis, properties and applications

As an important strategic resource, rare earths (REs) constitute 17 elements in the periodic table, namely 15 lanthanides (Ln) (La-Lu, atomic numbers from 57 to 71), scandium (Sc, atomic number 21) and yttrium (Y, atomic number 39). In the field of catalysis, the localization and incomplete filling of 4f electrons endow REs with unique physical and chemical properties, including rich electronic energy level structures, variable coordination numbers, etc., making them have great potential in electrocatalysis. Among various RE catalytic materials, rare earth oxide (REO)-based electrocatalysts exhibit excellent performances in electrocatalytic reactions due to their simple preparation process and strong structural variability. At the same time, the electronic orbital structure of REs exhibits excellent electron transfer ability, which can reduce the band gap and energy barrier values of rate-determining steps, further accelerating the electron transfer in the electrocatalytic reaction process; however, there is a lack of systematic review of recent advances in REO-based electrocatalysis. This review systematically summarizes the synthesis, properties and applications of REO-based nanocatalysts and discusses their applications in electrocatalysis in detail. It includes the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), hydrogen oxidation reaction (HOR), oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO2RR), methanol oxidation reaction (MOR), nitrogen reduction reaction (NRR) and other electrocatalytic reactions and further discusses the catalytic mechanism of REs in the above reactions. This review provides a timely and comprehensive summary of the current progress in the application of RE-based nanomaterials in electrocatalytic reactions and provides reasonable prospects for future electrocatalytic applications of REO-based materials.

Simultaneous catalytic oxidation of toluene and CO over Cu-V/Al-Ce catalysts: Physicochemical properties-activity relationship and simultaneous oxidation mechanism

Cu-V/Al-Ce with varying ratios of Al2O3/CeO2 were prepared to study the simultaneous catalytic oxidation of toluene and CO. Experimental results show that Cu-V/20Al-80Ce exhibits optimal simultaneous oxidation activity and good durability. This superior performance is related to Cu-Ce, V-Ce, and Al-Ce interactions, which facilitate the exposure of active centers, the creation of oxygen vacanicies, and efficient electron transfer. The mutual influence between toluene and CO during the simultaneous oxidation is then demonstrated. Toluene hinders CO oxidation through the competitive adsorption and the consumption of reactive oxygen species. CO enhances toluene oxidation, which is comprehensively explained by affecting the competition between the desorption and oxidation of benzaldehyde. Despite the mutual influence between toluene and CO, the pathways of CO and toluene oxidation are mutually independent. Toluene oxidation proceeds sequentially from toluene to benzyl alcohol, benzaldehyde, benzoate, and finally to CO2. Before being completely oxidized to CO2, CO is initially converted to carboxylic acid, hydrogen carbonate, free carbonate ion, bidentate formate, and monodentate carbonate.

Light-Reinforced Key Intermediate for Anticoking To Boost Highly Durable Methane Dry Reforming over Single Atom Ni Active Sites on CeO2

Dry reforming of methane (DRM) has been investigated for more than a century; the paramount stumbling block in its industrial application is the inevitable sintering of catalysts and excessive carbon emissions at high temperatures. However, the low-temperature DRM process still suffered from poor reactivity and severe catalyst deactivation from coking. Herein, we proposed a concept that highly durable DRM could be achieved at low temperatures via fabricating the active site integration with light irradiation. The active sites with Ni-O coordination (NiSA/CeO2) and Ni-Ni coordination (NiNP/CeO2) on CeO2, respectively, were successfully constructed to obtain two targeted reaction paths that produced the key intermediate (CH3O*) for anticoking during DRM. In particular, the operando diffuse reflectance infrared Fourier transform spectroscopy coupling with steady-state isotopic transient kinetic analysis (operando DRIFTS-SSITKA) was utilized and successfully tracked the anticoking paths during the DRM process. It was found that the path from CH3* to CH3O* over NiSA/CeO2 was the key path for anticoking. Furthermore, the targeted reaction path from CH3* to CH3O* was reinforced by light irradiation during the DRM process. Hence, the NiSA/CeO2 catalyst exhibits excellent stability with negligible carbon deposition for 230 h under thermo-photo catalytic DRM at a low temperature of 472 °C, while NiNP/CeO2 shows apparent coke deposition behavior after 0.5 h in solely thermal-driven DRM. The findings are vital as they provide critical insights into the simultaneous achievement of low-temperature and anticoking DRM process through distinguishing and directionally regulating the key intermediate species.

Supported Ce/Zr pyrochlore monolayers as a route to single cerium atom catalysts with low temperature reducibility

The combination of structural characterization at atomic resolution, chemical data, and theoretical insights has revealed the unique nanostructures which develop in ceria supported on yttria-stabilized zirconia (YSZ) after being submitted to high-temperature reducing treatments. The results show that just a small ceria loading is needed for creating a supported Zr-rich pyrochlore (111) nanostructure, resembling the structure of single cerium atom catalysts. The specific atomic arrangement of this nanostructure allows to explain the improvement of the reducibility at low temperature. The reduction mechanism can be extrapolated to ceria-zirconia mixed oxides with pyrochlore-like cationic ordering, exposing Zr-rich (111) surfaces. The results gathered here provide key information to understand the redox behavior of these types of systems, which may contribute to improving the design of new ceria-zirconia based materials, with lower content of the lanthanide element, nearly 100% cerium atom utilization, and applications in environmental catalysis.

Combining MSC Exosomes and Cerium Oxide Nanocrystals for Enhanced Dry Eye Syndrome Therapy

Dry eye syndrome (DES) is a prevalent ocular disorder involving diminishe·d tear production and increased tear evaporation, leading to ocular discomfort and potential surface damage. Inflammation and reactive oxygen species (ROS) have been implicated in the pathophysiology of DES. Inflammation is one core cause of the DES vicious cycle. Moreover, there are ROS that regulate inflammation in the cycle from the upstream, which leads to treatment failure in current therapies that merely target inflammation. In this study, we developed a novel therapeutic nanoparticle approach by growing cerium oxide (Ce) nanocrystals in situ on mesenchymal stem cell-derived exosomes (MSCExos), creating MSCExo-Ce. The combined properties of MSCExos and cerium oxide nanocrystals aim to target the "inflammation-ROS-injury" pathological mechanism in DES. We hypothesized that this approach would provide a new treatment option for patients with DES. Our analysis confirmed the successful in situ crystallization of cerium onto MSCExos, and MSCExo-Ce displayed excellent biocompatibility. In vitro and in vivo experiments have demonstrated that MSCExo-Ce promotes corneal cell growth, scavenges ROS, and more effectively suppresses inflammation compared with MSCExos alone. MSCExo-Ce also demonstrated the ability to alleviate DES symptoms and reverse pathological alterations at both the cellular and tissue levels. In conclusion, our findings highlight the potential of MSCExo-Ce as a promising therapeutic candidate for the treatment of DES.

Doped Ceria Nanomaterials: Preparation, Properties, and Uses

Doping is a powerful strategy for enhancing the performance of ceria (CeO2) nanomaterials in a range of catalytic, photocatalytic, biomedical, and energy applications. The present review summarizes recent developments in the doping of ceria nanomaterials with metal and non-metal dopants for selected applications. The most important metal dopants are grouped into s, p, d, and f block elements, and the relevant synthetic methods, novel properties, and key applications of metal doped ceria are collated and critically discussed. Non-metal dopants are similarly examined and compared with metal dopants using the same performance criteria. The review reveals that non-metal (N, S, P, F, and Cl) doped ceria has mainly been synthesized by calcination and hydrothermal methods, and it has found applications mostly in photocatalysis or as a cathode material for LiS batteries. In contrast, metal doped ceria nanomaterials have been prepared by a wider range of synthetic routes and evaluated for a larger number of applications, including as catalysts or photocatalysts, as antibacterial agents, and in devices such as fuel cells, gas sensors, and colorimetric detectors. Dual/co-doped ceria containing both metals and non-metals are also reviewed, and it is found that co-doping often leads to improved properties compared with single-element doping. The review concludes with a future outlook that identifies unaddressed issues in the synthesis and applications of doped ceria nanomaterials.

Technological solutions for NOx, SOx, and VOC abatement: recent breakthroughs and future directions

NOx, SOx, and carbonaceous volatile organic compounds (VOCs) are extremely harmful to the environment, and their concentrations must be within the limits prescribed by the region-specific pollution control boards. Thus, NOx, SOx, and VOC abatement is essential to safeguard the environment. Considering the importance of NOx, SOx, and VOC abatement, the discussion on selective catalytic reduction, oxidation, redox methods, and adsorption using noble metal and non-noble metal-based catalytic approaches were elaborated. This article covers different thermal treatment techniques, category of materials as catalysts, and its structure-property insights along with the advanced oxidation processes and adsorption. The defect engineered catalysts with lattice oxygen vacancies, bi- and tri-metallic noble metal catalysts and non-noble metal catalysts, modified metal organic frameworks, mixed-metal oxide supports, and their mechanisms have been thoroughly reviewed. The main hurdles and potential achievements in developing novel simultaneous NOx, SOx, and VOC removal technologies are critically discussed to envisage the future directions. This review highlights the removal of NOx, SOx, and VOC through material selection, properties, and mechanisms to further improve the existing abatement methods in an efficient way.

CeO2-CDs clusters decorated Co(OH)2 nanosheets for improved photocatalytic ammonia synthesis

The green synthesis process of photocatalytic ammonia production has received more and more attentions. Herein, a Z-scheme heterojunction with all-solid-state structures is constructed, in which carbon dots can act as electron transferring mediators. The photocatalytic measurement shows that the modified photocatalysts exhibit much higher activities, in which the ammonia production rates can reach above 232 µmol·g_cal^-1·h^-1 under the light irradiation. The improved catalytic properties can be credited to the significantly increased number of photoinduced oxygen vacancies, the excellent visible-light adsorption abilities and photogenerated electron-hole separation efficiencies for the carbon dots bridged heterostructures. More hydroxyl and superoxide radicals can be simultaneously produced in the composites. This work provides reasonable guidance for applications in photocatalytic ammonia synthesis and a promising construction strategy of efficient Z-scheme photocatalysts.

Ni, Co, and Yb Cation Co-doping and Defect Engineering of FeOOH Nanorods as an Electrocatalyst for the Oxygen Evolution Reaction

Electrocatalytic water splitting is a feasible technology that can produce hydrogen from renewable sources. The oxygen evolution reaction (OER), which has a slower kinetics and higher overpotential than the hydrogen evolution reaction, is the bottleneck that limits the overall water splitting. It is essential to develop efficient OER catalysts to reduce the anode overpotential. Herein, Ni,Co,Yb-FeOOH nanorod arrays grown directly on a carbon cloth are synthesized by a simple one-step hydrothermal method. The doped Ni²⁺ and Co²⁺ can occupy Fe²⁺ and Fe³⁺ sites in FeOOH, increasing the concentration of oxygen vacancies (V_O), and the doped Yb³⁺ with a larger ionic radius can occupy the interstitial sites, which leads to more edge dislocations. V_O and edge dislocations greatly enrich the active sites in FeOOH/CC. In addition, density functional theory calculations confirm that doping of Ni²⁺, Co²⁺, and Yb³⁺ modulates the electronic structure of the main active Fe sites, bringing its d-band center closer to the Fermi level and reducing the Gibbs free energy change of the rate-determining step of the OER. When the current density reaches 10 mA cm^-2, the overpotential of Ni,Co,Yb-FeOOH/CC is only 230.9 mV, and the Tafel slope is 22.7 mV dec^-1. In particular, a mechanism of multi-cation doping synergistic interaction with the oxygen vacancy and edge dislocation to enhance the OER catalytic activity of the material is proposed.

MOF-Derived CeO2 and CeZrOx Solid Solutions: Exploring Ce Reduction through FTIR and NEXAFS Spectroscopy

The development of Ce-based materials is directly dependent on the catalyst surface defects, which is caused by the calcination steps required to increase structural stability. At the same time, the evaluation of cerium's redox properties under reaction conditions is of increasing relevant importance. The synthesis of Ce-UiO-66 and CeZr-UiO-66 and their subsequent calcination are presented here as a simple and inexpensive approach for achieving homogeneous and stable CeO₂ and CeZrO_x nanocrystals. The resulting materials constitute an ideal case study to thoroughly understand cerium redox properties. The Ce³⁺/Ce⁴⁺ redox properties are investigated by H₂-TPR experiments exploited by in situ FT-IR and Ce M₅-edge AP-NEXAFS spectroscopy. In the latter case, Ce³⁺ formation is quantified using the MCR-ALS protocol. FT-IR is then presented as a high potential/easily accessible technique for extracting valuable information about the cerium oxidation state under operating conditions. The dependence of the OH stretching vibration frequency on temperature and Ce reduction is described, providing a novel tool for qualitative monitoring of surface oxygen vacancy formation. Based on the reported results, the molecular absorption coefficient of the Ce³⁺ characteristic IR transition is tentatively evaluated, thus providing a basis for future Ce³⁺ quantification through FT-IR spectroscopy. Finally, the FT-IR limitations for Ce³⁺ quantification are discussed.

Mesoporous Hollow Manganese Doped Ceria Nanoparticle for Effectively Prevention of Hepatic Ischemia Reperfusion Injury

Introduction

Hepatic ischemia-reperfusion injury (HIRI) is the main reason for liver dysfunction or failure after liver resection and liver transplantation. As excess accumulation of reactive oxygen species (ROS) is the leading factor, ceria nanoparticle, a cyclic reversible antioxidant, is an excellent candidate for HIRI.

Methods

Manganese doped mesoporous hollow ceria nanoparticles (MnO_x-CeO₂ NPs) were prepared, and the physicochemical characteristics, such as particle size, morphology, microstructure, etc. were elucidated. The in vivo safety and liver targeting effect were examined after i.v. injection. The anti-HIRI was determined by a mouse HIRI model.

Results

MnO_x-CeO₂ NPs with 0.40% Mn doped exhibited the strongest ROS-scavenging capability, which may due to the increased specific surface area and surface oxygen concentration. The nanoparticles accumulated in the liver after i.v. injection and exhibited good biocompatibility. In the HIRI mice model, MnO_x-CeO₂ NPs significantly reduced the serum ALT and AST level, decreased the MDA level and increased the SOD level in the liver, prevent pathological damages in the liver.

Conclusion

MnO_x-CeO₂ NPs were successfully prepared and it could significantly inhibit the HIRI after i.v. injection.

Reusable catalysts based on CeO2/cellulose derivative with visible light photocatalytic activity tuned by noble metal nanoparticles inclusion

For environmental preservation, it is crucial to effectively remove organic waste from water. Several approaches have been put forth, but photocatalysis stands out as a quick and effective solution. In this study, some hybrid polymeric structures that were created by photopolymerizing cellulose acetate/castor oil urethane methacrylates with embedded CeO₂ nanoparticles (NPs) and in situ photogenerated noble metal nanoparticles (Ag, Au, Pd) are characterized, and photochemically thoroughly evaluated. The effective modification of cellulose acetate with urethane methacrylate sequences and the degree of functionalization were first observed using ¹H NMR and FTIR spectra. Additionally, scanning and transmission electron microscopy, X-ray diffraction, FT-IR and UV-visible spectroscopy were utilized to analyse the resultant nanocomposites. The homogeneous dispersion of CeO₂ NPs (10-40 nm) into an organic matrix with the suitable functionalities, namely urethane and hydroxyl groups, favour the interfacial charge transfer reducing the E_g up to 2.85 eV. Moreover, noble metal nanoparticles (5-15 nm), such as Ag, Au and Pd introduction in nanocomposites, significantly lowered the E_g: 2.1 eV for CeAg samples, 1.7 eV for CeAu films and 1.5 eV for CePd films, respectively. This opens up new avenues for the creation of flexible cellulose-based photocatalysts that are active in visible light.

Recent advances in hydrothermal synthesis of facet-controlled CeO2-based nanomaterials

CeO₂-based nanomaterials have received tremendous attention due to their variety of applications. This paper is focused on the recent advances in facet-controlled CeO₂-based nanomaterials by the hydrothermal method. CeO₂-based nanomaterials with controllable size and exposed facets can be prepared by adjusting the reaction parameters. Moreover, doping and loading metals can improve the oxygen storage capacity (OSC) of CeO₂ and its catalytic activity. Various research studies on catalytic applications such as CO oxidation, water-gas shift reaction (WGSR), decomposition of hydrocarbons, and photocatalytic reaction have been carried out to exhibit the high potential of facet-controlled CeO₂ nanomaterials. This review will provide readers with various ideas for facet-controlled CeO₂-based nanomaterials.

The two-step electrosynthesis of nanocomposites of Ag, Au, and Pd nanoparticles with iron(ii) oxide-hydroxide

The two-step electrosynthesis of metal nanoparticle (MNP, M = Ag, Pd, and Au) nanocomposites with iron oxide-hydroxide FeO-xFe(OH)2 was investigated.

Insight into the Morphology-Dependent Catalytic Performance of CuO/CeO2 Produced by Tannic Acid for Efficient Hydrogenation of 4-Nitrophenol

The construction of a heterogeneous nanocatalyst with outstanding catalytic performance via an environmentally benign and cost-effective synthetic category has long been one of the challenges in nanotechnology. Herein, we synthesized highly efficient and low-cost mesoporous morphology-dependent CuO/CeO₂ -Rods and CuO/CeO₂ -Cubes catalysts by employing a green and multifunctional polyphenolic compound (tannic acid) as the stabilizer and chelating agent for 4-nitrophenol (4-NP) reduction reaction. The CuO/CeO₂ -Rods exhibited excellent performance, of which the activity was 3.2 times higher than that of CuO/CeO₂ -Cubes. This can be connected with the higher density of oxygen vacancy on CeO₂ -Rods (110) than CeO₂ -Cubes (100), the oxygen vacancy favors anchoring CuO species on the CeO₂ support, which promotes the strong interaction between finely dispersed CuO and CeO₂ -Rods at the interfacial positions and facilitates the electron transfer from BH₄ ^- to 4-NP. The synergistic catalytic mechanism illustrated that 4-NP molecules preferentially adsorbed on the CeO₂ , while H₂ from BH₄ ^- dissociated over CuO to form highly active H* species, contributing to achieving efficient hydrogenation of 4-NP. This study is expected to shed light on designing and synthesizing cost-effective and high-performance nanocatalysts through a greener synthetic method for the areas of catalysis, nanomaterial science and engineering, and chemical synthesis.

Nanotechnological approaches as a promising way for heavy metal mitigation in an aqueous system

The ever-rising environmental problems because of heavy metals emerging from anthropogenic activities pose an impending threat to all biota globally. Considering their persistence and possibility in biomagnification, they are prominent among pollutants. There has been an apparent shift of research interest in advancing cost-effective and competent technologies to mitigate environmental contaminants, specifically heavy metals. In the recent two decades, tailored nanomaterials (NMs), nanoparticles, and NM-based adsorbents have been emerging for removing heavy metal pollution on a sustainable scale, especially the green synthesis of these nanoproducts effective and nonhazardous means. Hence, this review explores the various avenues in nanotechnology, an attempt to gauge nanotechnological approaches to mitigate heavy metals in the aqueous system, especially emphasizing the recent trends and advancements. Inputs on remediating heavy metal in sustainable and environmentally benign aspects recommended future directions to compensate for the voids in this domain have been addressed.

Insights into the Interfacial Lewis Acid-Base Pairs in CeO2 -Loaded CoS2 Electrocatalysts for Alkaline Hydrogen Evolution

Despite the known efficacy of CeO₂ as a promoter in alkaline hydrogen evolution reaction (HER), the underlying mechanism of this effect remains unclear. CoS₂ , a pyrite-type alkaline HER electrocatalyst, suffers from sluggish HER kinetics and severe catalyst leaching due to its weak water dissociation kinetics and oxygen-related corrosion. Herein, it is demonstrated that the interfacial Lewis acid-base Ce∙∙∙S pairs in CeO₂ -loaded CoS₂ effectively improve the catalytic activity and durability. In CeO₂ -loaded CoS₂ nanowire array electrodes, these interfacial Lewis acid-base Ce∙∙∙S pairs with unique electronic and structural configurations efficiently activate water adsorptive dissociation and kinetically accelerate hydrogen evolution, delivering a low overpotential of 36 mV at 10 mA cm^-2 in alkaline media. Such Ce∙∙∙S pairs also weaken O₂ adsorption on CoS₂ , leading to undecayed activity over 1000 h. These findings are expected to provide guidance for the design of CeO₂ -based electrocatalysts as well as other hybrid electrocatalysts for water splitting.

Uncovering the Promotion of CeO2 /CoS1.97 Heterostructure with Specific Spatial Architectures on Oxygen Evolution Reaction

Structural engineering and compositional controlling are extensively applied in rationally designing and fabricating advanced freestanding electrocatalysts. The key relationship between the spatial distribution of components and enhanced electrocatalysis performance still needs further elaborate elucidation. Here, CeO₂ substrate supported CoS_1.97 (CeO₂ -CoS_1.97 ) and CoS_1.97 with CeO₂ surface decorated (CoS_1.97 -CeO₂ ) materials are constructed to comprehensively investigate the origin of spatial architectures for the oxygen evolution reaction (OER). CeO₂ -CoS_1.97 exhibits a low overpotential of 264 mV at 10 mA cm^-2 due to the stable heterostructure and faster mass transfer. Meanwhile, CoS_1.97 -CeO₂ has a smaller Tafel slope of 49 mV dec^-1 through enhanced adsorption of OH^- , fast electron transfer, and in situ formation of Co(IV)O₂ species under the OER condition. Furthermore, operando spectroscopic characterizations combined with theoretical calculations demonstrate that spatial architectures play a distinguished role in modulating the electronic structure and promoting the reconstruction from sulfide to oxyhydroxide toward higher chemical valence. The findings highlight spatial architectures and surface reconstruction in designing advanced electrocatalytic materials.

Enhanced adsorption and degradation of methylene blue over mixed niobium-cerium oxide - Unraveling the synergy between Nb and Ce in advanced oxidation processes

Formation of reactive oxygen species (ROS) via H₂O₂ activation is of vital importance in catalytic environmental chemistry, especially in degradation of organic pollutants. A new mixed niobium-cerium oxide (NbCeO_x) was tailored for this purpose. A thorough structural and chemical characterization of NbCeO_x along with CeO₂ and Nb₂O₅ reference materials was carried out using TEM/STEM/EDS, SEM, XRD, XPS, EPR, UV-vis and N₂ physisorption. The ability of the catalysts to activate H₂O₂ towards ROS formation was assessed on the basis of EPR and Raman measurements. Catalytic activity of the oxides was evaluated in degradation of methylene blue (MB) as a model pollutant. Very high activity of NbCeO_x was attributed to the mixed redox-acidic nature of its surface, which originated from the synergy between Nb and Ce species. These two properties (redox activity and acidity) ensured convenient conditions for efficient activation of H₂O₂ and degradation of MB. The activity of NbCeO_x in MB degradation was found 3 times higher than that of the commercial Nb₂O₅ CBMM catalyst and 240 times higher than that of CeO₂. The mechanism of the degradation reaction was found to be an adsorption-triggered process initiated by hydroxyl radicals, generated on the surface via the transformation of O₂^-•/O₂^2-.

Noble-Metal-Free Multicomponent Nanointegration for Sustainable Energy Conversion

Global energy and environmental crises are among the most pressing challenges facing humankind. To overcome these challenges, recent years have seen an upsurge of interest in the development and production of renewable chemical fuels as alternatives to the nonrenewable and high-polluting fossil fuels. Photocatalysis, photoelectrocatalysis, and electrocatalysis provide promising avenues for sustainable energy conversion. Single- and dual-component catalytic systems based on nanomaterials have been intensively studied for decades, but their intrinsic weaknesses hamper their practical applications. Multicomponent nanomaterial-based systems, consisting of three or more components with at least one component in the nanoscale, have recently emerged. The multiple components are integrated together to create synergistic effects and hence overcome the limitation for outperformance. Such higher-efficiency systems based on nanomaterials will potentially bring an additional benefit in balance-of-system costs if they exclude the use of noble metals, considering the expense and sustainability. It is therefore timely to review the research in this field, providing guidance in the development of noble-metal-free multicomponent nanointegration for sustainable energy conversion. In this work, we first recall the fundamentals of catalysis by nanomaterials, multicomponent nanointegration, and reactor configuration for water splitting, CO₂ reduction, and N₂ reduction. We then systematically review and discuss recent advances in multicomponent-based photocatalytic, photoelectrochemical, and electrochemical systems based on nanomaterials. On the basis of these systems, we further laterally evaluate different multicomponent integration strategies and highlight their impacts on catalytic activity, performance stability, and product selectivity. Finally, we provide conclusions and future prospects for multicomponent nanointegration. This work offers comprehensive insights into the development of cost-competitive multicomponent nanomaterial-based systems for sustainable energy-conversion technologies and assists researchers working toward addressing the global challenges in energy and the environment.

Facile one-pot synthesis of carbon self-doped graphitic carbon nitride loaded with ultra-low ceric dioxide for high-efficiency environmental photocatalysis: Organic pollutants degradation and hexavalent chromium reduction

In the present study, an innovative carbon self-doped g-C₃N₄ (CCN) loaded with ultra-low CeO₂ (0.067-0.74 wt%) composite photocatalyst is successfully synthesized via a facile one-pot hydrothermal and calcination method. The CeO₂/CCN exhibits superior photocatalytic performance for tetracycline degradation (78.9% within 60 min), H₂O₂ production (151.92 μmol L^-1 within 60 min), and Cr(VI) reduction (99.5% within 40 min), which much higher than that of g-C₃N₄, CCN, CeO₂, and CeO₂/g-C₃N₄. The enhanced photocatalytic performance is originated from the fact that the doping of C can efficaciously broaden the utilization range of solar light and improve the reduction ability of photogenerated electrons. Meanwhile, the ultra-low loading of CeO₂ can effectually promote the migration of photogenerated electrons and enhance the specific surface area. Besides, the experiments of pH effect and cycle ability indicate that CeO₂/CCN has excellent durability and stability. Finally, the photocatalytic mechanism of CeO₂/CCN is systematically discussed. This work proves that combining element doping and semiconductor coupling is a promising strategy to design high-efficiency g-C₃N₄-based photocatalysts.