CeO2 Nanowires Research Articles

Enhanced low-temperature catalytic activity and stability in methane combustion of Pd−CeO2 nanowires@SiO2 by Pt dispersion

The long-standing contradiction between low-temperature activity and high-temperature stability is one of the difficulties in catalytic combustion of low-concentration methane. The traditional Pd−CeO2 catalyst system has been applied to the oxidation of methane with low concentrations. However, the problem of sintering at high temperatures still exists. In this work, we prepared the Pt-modified Pd−CeO2 nanowires (NW) sample (in which the actual Pt, Pd, and Ce contents were 0.12, 0.86, and 9.8 wt%, respectively) using the one-pot reverse-micelle emulsion method. It was found that Pt-Pd−CeO2NW@SiO2 showed the highest low-temperature catalytic activity at a space velocity of 20,000 mL/(g h) and the best water resistance and high-temperature stability in the combustion of methane. The T50 % and T90 % (the temperatures for achieving methane conversions of 50 and 90 %) were 298 and 342 ℃, respectively, methane reaction rate at 270 ℃ was 0.49 μmol/(gcat s), and turnover frequency (TOF) at 270 °C was 0.198 s−1 over Pt-Pd−CeO2NW@SiO2; whereas over Pd−CeO2NW@SiO2 (in which the actual Pd and Ce contents were 0.82 and 10.6 wt%, respectively), the T50 % and T90 % were 360 and 420 ℃, respectively, methane reaction rate at 270 ℃ was 0.074 μmol/(gcat s), and TOF at 270 °C was 0.032 s−1. The introduction of the highly dispersed Pt to Pd−CeO2NW@SiO2 could effectively increase the PdOx sites of unsaturated coordination through the electron-donating interaction of the Pt with PdO, which played an important role in activating the C−H bonds in methane. In addition, the unique structure of encapsulation also rendered the Pt-Pd−CeO2NW@SiO2 sample to possess good water resistance and thermal stability in methane combustion. We are sure that the present work provides a possibility for developing the catalysts with stable catalytic and water-resistant performance at low and high temperatures in the combustion of methane.

One-pot Synthesis of PdCuAg and CeO2 Nanowires Hybrid with Abundant Heterojunction Interface for Ethylene Glycol Electrooxidation.

Introducing CeO2 into Pd-based nanocatalysts for electrocatalytic reactions is a good way to solve the intermediate toxicity problem and improve the catalytic performance. Here we reported a simple strategy to synthesize the PdCuAg and CeO2 nanowires hybrid via a one-pot synthesis process under strong nanoconfined effect of specific surfactant as templates. Owing to the structural (ultrathin nanowires, abundant heterojunction/interfaces between metal and metal oxide) and compositional (Pd, Cu, Ag, CeO2) advantages, the hybrid showed significantly enhanced catalytic activity (6.06 A mgPd -1) and stability, accelerated reaction rate, and reduced activation energy toward electrocatalytic ethylene glycol oxidation reaction.

Customizing Wettability of Defect-Rich CeO2/TiO2 Nanotube Arrays for Humidity-Resistant, Ultrafast, and Sensitive Ammonia Response.

In all their applications, gas sensors should satisfy several requirements, including low cost, reduced energy consumption, fast response/recovery, high sensitivity, and reliability in a broad humidity range. Unfortunately, the fast response/recovery and sensing reliability under high humidity conditions are often still missing, especially those working at room temperature. In this study, a humidity-resistant gas sensor with an ultrafast response/recovery rate was designed by integrating a defect-rich semiconducting sensing interface and a self-assembled monolayer (SAM) with controllable wettability. As a proof-of-concept application, ammonia (NH3), one of the atmospheric and indoor pollutants, was selected as the target gas. The decoration of interconnected defective CeO2 nanowires on spaced TiO2 nanotube arrays (NTAs) provided superior NH3 sensing performances. Moreover, we showed that manipulating the functional end group of SAMs is an efficient and simple method to adjust the wettability, by which 86% sensitivity retention with an ultrafast response (within 5 s) and a low limit of detection (45 ppb) were achieved even at 75% relative humidity and room temperature. This work provides a new route toward the comprehensive design and application of metal oxide semiconductors for trace gas monitoring under harsh conditions, such as those of agricultural, environmental, and industrial fields.

Composite Solid Electrolyte with Continuous and Fast Organic-Inorganic Ion Transport Highways Created by 3D Crimped Nanofibers@functional Ceramic Nanowires.

A 3D crimped sulfonated polyethersulfone-polyethylene oxide(C-SPES/PEO) nanofiber membrane and long-range lanthanum cobaltate(LaCoO3 ) nanowires are collectively doped into a PEO matrix to acquire a composite solid electrolyte (C-SPES-PEO-LaCoO3 ) for all-solid-state lithium metal batteries(ASSLMBs). The 3D crimped structure enables the fiber membrane to have a large porosity of 90%. Therefore, under the premise of strongly guaranteeing the mechanical properties of C-SPES-PEO-LaCoO3 , the ceramic nanowires conveniently penetrated into the 3D crimped SPES nanofiber without being blocked, which can facilitate fast ionic conductivity by forming 3D continuous organic-inorganic ion transport pathways. The as-prepared electrolyte delivers an excellent ionic conductivity of 2.5 × 10-4 Scm-1 at 30°C. Density functional theory calculations indicate that the LaCoO3 nanowires and 3D crimped C-SPES/PEO fibers contribute to Li+ movement. Particularly, the LiFePO4 /C-SPES-PEO-LaCoO3 /Li and NMC811/C-SPES-PEO-LaCoO3 /Li pouch cell have a high initial discharge specific capacity of 156.8mAhg-1 and a maximum value of 176.7mAhg-1 , respectively. In addition, the universality of the penetration of C-SPES/PEO nanofibers to functional ceramic nanowires is also reflected by the stable cycling performance of ASSLMBs based on the electrolytes, in which the LaCoO3 nanowires are replaced with Gd-doped CeO2 nanowires. The work will provide a novel approach to high performance solid-state electrolytes.

Efficient CO2 fixation with acetophenone on Ag-CeO2 electrocatalyst by a double activation strategy

AbstractThe electrocarboxylation reaction is an attractive means to convert CO2 into valuable chemicals under ambient conditions, while it still suffers from low efficiency due to the high stability of CO2. In this work, we report a double activation strategy for simultaneously activating CO2 and acetophenone by silver-doped CeO2 (Ag-CeO2) nanowires, featuring as an effective electrocatalyst for electrocarboxylation of acetophenone with CO2. Compared to the Ag foil, Ag nanoparticles and CeO2 nanowires, the Ag-CeO2 nanowire catalyst allowed to reduce the onset potential difference between CO2 and acetophenone activation, thus enabling efficient electrocarboxylation to form 2-phenyllactic acid. The Faradaic efficiency for producing 2-phenyllactic acid reached 91% at −1.8 V versus Ag/AgI. This double activation strategy of activating both CO2 and organic substrate molecules can benefit the catalyst design to improve activities and selectivities in upgrading CO2 fixation for higher-value electrocarboxylation.

Oxygen vacancy engineering on cerium oxide nanowires for room-temperature linalool detection in rice aging

It is a huge challenge for metal oxide semiconductor gas sensors to inspect volatile organic compounds (VOCs) at room temperature (RT). Herein, the effective utilization of cerium oxide (CeO2) nanowires for RT detection of VOCs was realized via regulating its surface chemical state. Oxygen vacancy engineering on CeO2 nanowires, synthesized via hydrothermal method, can be manipulated by annealing under various controlled atmospheres. The sample annealed under 5%H2+95%Ar condition exhibited outstanding RT sensing properties, displaying a high response of 16.7 towards 20 ppm linalool, a fast response and recovery time (16 and 121 s, respectively), and a low detection of limit of 0.54 ppm. The enhanced sensing performance could be ascribed for the synergistic effects of its nanowire morphology, the large specific surface area (83.95 m2/g), and the formation of extensive oxygen vacancy accompanied by an increase in Ce3+. Additionally, the practicability of the sensor was verified via two varieties of rice (Indica and Japonica rice) stored in various periods (1, 3, 5, 7, 15, and 30 d). The experimental results revealed that the sensor was able to distinguish Indica rice from Japonica rice. Accordingly, the as-developed sensor delivers a strategic material to develop high-performance RT electronic nose equipment for monitoring rice quality.

Optimized CeO2 Nanowires with Rich Surface Oxygen Vacancies Enable Fast Li‐Ion Conduction in Composite Polymer Electrolytes

Low‐cost and flexible solid polymer electrolytes are promising in all‐solid‐state Li‐metal batteries with high energy density and safety. However, both the low room‐temperature ionic conductivities and the small Li+ transference number of these electrolytes significantly increase the internal resistance and overpotential of the battery. Here, we introduce Gd‐doped CeO2 nanowires with large surface area and rich surface oxygen vacancies to the polymer electrolyte to increase the interaction between Gd‐doped CeO2 nanowires and polymer electrolytes, which promotes the Li‐salt dissociation and increases the concentration of mobile Li ions in the composite polymer electrolytes. The optimized composite polymer electrolyte has a high Li‐ion conductivity of 5 × 10−4 S cm−1 at 30 °C and a large Li+ transference number of 0.47. Moreover, the composite polymer electrolytes have excellent compatibility with the metallic lithium anode and high‐voltage LiNi0.8Mn0.1Co0.1O2 (NMC) cathode, providing the stable cycling of all‐solid‐state batteries at high current densities.

Microporous‐Ceria‐Wrapped Gold Nanoparticles for Conductometric and SERS Dual Monitoring of Hazardous Gases at Room Temperature

AbstractThis work proposes a novel and simple synthesis method for microporous‐ceria‐wrapped gold (Au@mp‐CeO2) nanoparticles (NPs) based on linker molecule‐induced stacking of ultrafine CeO2 particles (or beads) on the surface of pre‐prepared gold NPs. The resulting NPs have a uniform size and microporous CeO2 shells with a mean thickness of 28 nm and porosity of 42%. The shell is highly tunable from about 4 to 30 nm thick. This method is universal and suitable for other metal@mp‐oxide nanoarchitectures (such as Au@mp‐CuO NPs, Au@mp‐Cr2O3 NPs, Ag@mp‐CeO2 NPs, and Ag@mp‐CeO2 nanowires) simply via changing the pre‐prepared metal cores or shell precursors. Most significantly, the as‐prepared Au@mp‐CeO2 NPs can be used for accurate monitoring of toluene vapor (10 ppm level) at room temperature based on their conductometric and surface‐enhanced Raman spectroscopy (SERS) dual response. Moreover, these NPs can be also used for other hazardous gases, such as chlorobenzene, hydrogen sulfide, and 1‐dodecanethiol. This excellent performance benefits from the micropore‐enhanced interaction between CeO2 and gas molecules. This work not only provides new and controllable preparation for metal@mp‐oxide nanoarchitectures, but also demonstrates the great potential applications of these materials in real‐time and identifiable monitoring of hazardous gases.

Green synthesized CeO2 nanowires immobilized with alginate-ascorbic acid biopolymer for advance oxidative degradation of crystal violet

The study reports the synthesis of cerium oxide (CeO2) nanowires functionalized with a blend of ascorbic acid–alginate biopolymer via chemical coprecipitation method. The material was characterized by FTIR, XRD, SEM-EDX, DSC, DLS and UV-Vis spectroscopy. The X-ray data obtained suggested a cubic fluorite structure of CeO2 which is little bit mitigated due to functionalization by organic moieties of ascorbic acid–alginate blends. The band gap energy Eg value of the material using UV-Vis spectroscopy associated with Tauc’s plot was found to be 2.56 eV. The synthesized material was further explored as a photocatalyst for the degradation of crystal violet dye under visible light. The synergistic and antagonistic effect of various reaction parameters like irradiation time (10–110 min), pH (2.6–9.3) and catalyst dose (1.59–18.5 mg) on CV degradation was observed under response surface methodology coupled with central composite design in a vicinity of 95% confidence interval and desirability of 1.0. The experimental data suggested that the photocatalysis was controlled by pseudo first order kinetics and hydroxyl radical (•OH radicals) was acting as primary ROS resulting in 99.52% degradation of CV. The material we are reporting in our manuscript has not been reported anywhere in the literature. Very few studies are there in literature which explored the properties of biopolymer for nanomaterial synthesis and stabilization. The surface functionalization of CeO2 not only provided stabilization but also enhanced their photocatalytic activities towards crystal violet dye. The computational modeling and optimization reaction for photocatalytic studies are purely novel.

Diameter dependent thermodynamics of adsorption on nanowires: A theoretical and experimental study

Because the influencing mechanism and regularity of diameter on the adsorption thermodynamics of nanowires are still unclear, the relations of adsorption thermodynamic properties of different diameters of nanowires is derived. Experimentally, we prepared CeO2 nanowires with different diameters, and then the adsorption selectivity of CeO2 nanowires to different dyes was researched. The adsorption thermodynamic properties of dyes with the best adsorption selectivity were determined, and the influences of the diameter on the adsorption thermodynamic properties were discussed. The experimental results show that the adsorption capacity for congo red is the strongest and that for methylene blue is the weakest. In addition, with the decreases of diameter of CeO2 nanowires, the adsorption capacity and the adsorption Equilibrium constant increase, while ΔadsGmo, ΔadsHmo and ΔadsSmo decrease, and this thermodynamic properties are linearly related to the reciprocal of diameter, respectively. The experimental results agree with the thermodynamic theory of nanowire adsorption.

Methane decomposition for hydrogen production over biomass fly ash-based CeO2 nanowires promoted cobalt catalyst

In this work, the biomass fly ash (BFA) was investigated as a potential catalyst for the thermo-catalytic decomposition of methane and attractive approach for hydrogen (H2) production. The BFA based CeO2 nanowires promoted cobalt catalyst was synthesized for catalytic methane (CH4) decomposition and was tested in a fixed bed reactor. The physicochemical properties of the catalyst were investigated using various techniques such as X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, thermal gravimetric analysis, and Fourier transformed infrared. The pure crystalline micro-flake BFA was modified using synthesized CeO2 nanowires and the resulted micro flakes cross-linked with nanowires shown thermal stability up to 900 °C. The high stability of the catalyst makes it suitable for the thermal catalytic decomposition of methane. The activity of the catalyst was tested at 850 °C to analyze the H2 production and CH4 conversion. The obtained results revealed that support and promoter exhibit a strong impact on the CH4 conversion and H2 yield in catalyst screening tests. A maximum conversion of 71% for CH4 with 44.9% H2 yield was recorded for 34 h on stream activity while using 5% Co/CeO2-BFA as the catalyst. While BFA and Co-BFA as catalyst showed 36% and 47% conversion of CH4, respectively which indicates that the addition of promoter shows an increase in values of both conversion of CH4 and H2 yield. Compared to traditional catalyst support, the use of waste-sourced catalyst support for CH4 decomposition provides a greener and more economical route for H2 production.

Cerium oxide-sulfur nanohybrids: Combining the robust adsorption of polysulfides with enhanced redox kinetics to improve the energy Storage capabilities of Li-S batteries

An in-depth investigation of the physical and chemical parameters that affect Li-sulfur batteries is imperative to optimize their performances. Here, we report promising [CeO2]100-x-[S8]x nanohybrids for anchoring lithium polysulfides (LiPSs) that are generated during cycling. The composition of [CeO2]100- x-[S8]x (x = 30, 50 and 70%) could be simply controlled by varying the CeO2/S8 mass ratio added in each reaction. Our results indicated that the [CeO2]100- x-[S8]x nanohybrids displayed a crystalline structure composed of both phases (CeO2 and S8), indicating an efficient impregnation process of S8 on the CeO2 nanowire surface. The surface area of CeO2 nanowires decreased as the amount of S8 was increased, and the [CeO2]70-[S8]30 nanohybrid maintained a uniform distribution of S8 over the entire CeO2 nanowires. Remarkably, the [CeO2]70-[S8]30 nanohybrid showed the best Li-storage performance, leading to specific capacities of approximately 600 mA h g–1 over 160 cycles and a Coulombic efficiency of approximately 100%. Moreover, this sample showed excellent rate capability performance (even discharging at 10 A g–1). Additionally, the chemical interaction of CeO2 with LiPS was demonstrated by a visual experiment through the addition of pure CeO2 in a solution of Li2S6. The solution containing CeO2 nanowires became completely colorless after 30 min. To further investigate these improvements, density functional theory (DFT) calculations revealed the formation of strong interactions between the CeO2 nanowire surface and different sulfur species. For instance, the adsorption energies between the CeO2 nanowires and S8, Li2S4, and Li4S8 were –3.95, –5.84 and –7.31 eV, respectively, suggesting that the [CeO2]70-[S8]30 nanohybrid provided an appropriate surface to anchor LiPS by electrostatic interactions, leading to faster redox kinetics in Li-sulfur battery applications.

Synergistic effect between CeO2 nanowires and gold NPs over the activity and selectivity in the oxidation of thioanisole

Gold nanoparticles incorporated on ceria nanowires have been employed as efficient nanocatalysts for the selective oxidation of thioanisole. The control of both physical and chemical parameters as well as metal–support interactions are important factors that determine their performances. Considering their one-dimensional morphology with large surface area, thin diameters, high concentration of oxygen vacancies, and small Au NPs uniformly on the entire CeO2 surface with a high fraction of oxidized gold species, these characteristics make them favorable nanocatalysts for oxidation transformations. The CeO2-Au nanowires displayed improved performances towards the oxidation of thioanisole when compared to the pure CeO2 nanowires and commercial CeO2-Au catalysts. The CeO2-Au nanowires catalyzed the selective synthesis of methyl phenyl sulfoxide with up to 100 % of selectivity and high conversion. The impact of solvent and temperature during the catalytic reaction was also experimentally and theoretically investigated by DFT calculations, indicating a key role in the observed activities.

Towards the Effect of Pt0/Ptδ+ and Ce3+ Species at the Surface of CeO2 Crystals: Understanding the Nature of the Interactions under CO Oxidation Conditions

AbstractWe synthesized CeO2 nanowires and nanocubes showing {110}+{100} and {100} surfaces predominantly, respectively, once the different surface energies play a crucial role in the behavior of Ce4+/Ce3+ reversibility. We found out that Pt/CeO2 nanowires presented more Ce3+ content, oxygen vacancies, and atomically dispersed Pt, indicating a stronger Pt−Ce interaction. In contrast, the Pt/CeO2 nanocubes presented a higher contribution of Ptδ+ species, suggesting a well‐controlled Pt particle size (∼1 nm) and significant interaction with ceria, with oxygen species more available at the surface. Thus, we suggest that the ceria‘s different surface energies may lead to different Pt distributions of species over the supports. H2‐reduction treatment led to changes in Pt structure that showed a better catalysis performance for the Pt/CeO2 nanowires essentially, supported by XPS and CO‐DRIFTS. Nevertheless, this step did not cause improved activity to the point of overcoming the nanocubes‐based catalyst, and the reasons were fully discussed. Herein, we propose that catalysts′ performance depends on a complex combination of several materials′ characteristics. These features may lead to different reaction pathways depending on the pre‐treatment of the samples.

Heterostructural Co/CeO2/Co2P/CoP@NC dodecahedrons derived from CeO2-inserted zeolitic imidazolate framework-67 as efficient bifunctional electrocatalysts for overall water splitting

The design and fabrication of highly active, robust and cost-efficient electrocatalysts for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is of great significance towards overall water splitting, but remains challenging as well. Herein, we report, for the first time, heterostructural Co/CeO2/Co2P/CoP@NC dodecahedrons as bifunctional electrocatalyst, in which abundant interfaces are formed between different components. Typical ZIF-67 (ZIF = zeolitic imidazolate framework) dodecahedrons with pre-inserted CeO2 nanowires were selected as precursors to synthesize Co/CeO2/Co2P/CoP@NC via a direct carbonization process followed by phosphidation, simultaneously generating the strong coupled heterojunction interfaces through interactions between CeO2 and CoxP species. Abundant porous structure leads to the exposure of more active sites and the carbon encapsulation of nanodomains sustains the high robustness and conductivity and the synergistic effect between the multi-components heterostructure. Benefiting from the above collective advantages, the Co/CeO2/Co2P/CoP@NC electrocatalysts exhibit small overpotentials of 307 and 195 mV to derive 10 mA cm−2 for OER and HER, respectively. Furthermore, an alkaline electrolyzer assembled by using Co/CeO2/Co2P/CoP@NC as both cathode and anode can achieve a current density of 10 mA cm−2 at a low voltage of 1.76 V and work continuously for over 15 h. This work would provide a rational protocol for fabrication multi-phase interface enriched electrocatalysts toward highly efficient energy conversion.

Europium-Doped Ceria Nanowires as Anode for Solid Oxide Fuel Cells

CeO2-based materials have been studied intensively as anodes for intermediate temperature solid oxide fuel cells (IT-SOFCs). In this work, pristine and europium (Eu)-doped CeO2 nanowires were comprehensively investigated as anode materials for IT-SOFCs, by a combination of theoretical predictions and experimental characterizations. The results demonstrate: (1) Oxygen vacancies can be energetically favorably introduced into the CeO2 lattice by Eu doping; (2) The lattice parameter of the ceria increases linearly with the Eu content when it varies from 0 to 35 mol.%, simultaneously resulting in a significant increase in oxygen vacancies. The concentration of oxygen vacancies reaches its maximum at a ca. 10 mol.% Eu doping level and decreases thereafter; (3) The highest oxygen ion conductivity is achieved at a Eu content of 15 mol.%; while the 10 mol.% Eu-doped CeO2 sample displays the highest catalytic activity for H2-TPR and CO oxidization reactions. The conducting and catalytic properties benefit from the expanded lattice, the large amount of oxygen vacancies, the enhanced reactivity of surface oxygen and the promoted mobility of bulk oxygen ions. These results provide an avenue toward designing and optimizing CeO2 as a promising anode for SOFCs.

Nickel-Ceria Nanowires Embedded in Microporous Silica: Controllable Synthesis, Formation Mechanism, and Catalytic Applications.

Designing highly efficient catalysts for use in fuel production is a highly attractive research area but still remains challenging. Herein, for the first time, ultrafine Ni nanoparticles (NPs) self-assembled on ceria nanowires (NWs) and then embedded in a microporous silica shell (denoted as Ni-CeO2@SiO2) are successfully designed and synthesized via a one-pot facile strategy. The average diameter of Ni-CeO2 NWs is just 2.9 nm, and the length is up to 102.7 nm. The resulting Ni-CeO2@SiO2 exhibits high performance and 100% hydrogen selectivity for H2 production from N2H4 and N2H4BH3 in aqueous solution. Unexpectedly, Ni-CeO2@SiO2 also has good catalytic performance and thermal stability for CO2 methanation. The high catalytic performance of Ni-CeO2@SiO2 can be attributed to the synergistic electronic effect and strong interaction between Ni NPs and CeO2 NWs with plenty of oxygen vacancies, as well as the unique structure effect. As an effective strategy, the present work provides an opportunity to embed ultrafine metal NPs-CeO2 NWs into a microporous silica shell, which has broad application prospects in various catalytic fields.

High-efficiency direct methane conversion to oxygenates on a cerium dioxide nanowires supported rhodium single-atom catalyst

Direct methane conversion (DMC) to high value-added products is of significant importance for the effective utilization of CH4 to combat the energy crisis. However, there are ongoing challenges in DMC associated with the selective C−H activation of CH4. The quest for high-efficiency catalysts for this process is limited by the current drawbacks including poor activity and low selectivity. Here we show a cerium dioxide (CeO2) nanowires supported rhodium (Rh) single-atom (SAs Rh-CeO2 NWs) that can serve as a high-efficiency catalyst for DMC to oxygenates (i.e., CH3OH and CH3OOH) under mild conditions. Compared to Rh/CeO2 nanowires (Rh clusters) prepared by a conventional wet-impregnation method, CeO2 nanowires supported Rh single-atom exhibits 6.5 times higher of the oxygenates yield (1231.7 vs. 189.4 mmol gRh−1 h−1), which largely outperforms that of the reported catalysts in the same class. This work demonstrates a highly efficient DMC process and promotes the research on Rh single-atom catalysts in heterogeneous catalysis.

Near-visible-light-driven noble metal-free of reduced graphene oxide nanosheets over CeO2 nanowires for hydrogen production

This study is the first to use a newly-developed material via hydrothermal method, cerium oxide nanowires doped with reduced graphene oxide (CNW-RGO) for reductive H2 production. The detailed characteristics of the CNW-RGO materials were investigated to explore the capabilities of reductive production. The mean diameter of the CNWs was uniform at 22 nm. Owing to RGO-doping, the energy gap between the valence and conduction bands tended to become narrower that demonstrated by the density functional theory calculation (DFT). Furthermore, the optimum hydrogen production was 7.14 mmol g−1 by the CNW-RGO with a RGO content of 4 wt.% under the visible-light irradiation. This result was consistent with the turnover frequency (TOF) predictions. The introduction of RGO sheets effectively mediated the transfer of photogenerated electrons from the CNW to the sheets. Therefore, it could act as an electron trap to stimulate charge separation, which was corroborated by X-ray photoelectron spectroscopy (XPS) analysis. As indicated by comparative assessment, methanol was the most promising sacrificial agent in the system. Additionally, the formation of the methoxy group after the reaction was clearly demonstrated by Fourier-transform infrared (FTIR) spectroscopy. The number of hydroxyl groups on the alcohols directly determined their activity in reductive production.

Active and stable Pt-Ceria nanowires@silica shell catalyst: Design, formation mechanism and total oxidation of CO and toluene

Cerium oxide is one of the most important rare earth metal oxides in catalysis, however, the sintering problem of noble metals and CeO2 at higher temperature (e.g., >700 °C) is still unresolved. Herein, Pt nanoparticles self-assembled on ultra-thin CeO2 nanowires (NWs) and then confined inside a thermally robust porous silica shell (Pt-CeO2NW@SiO2) were introduced. The thickness of CeO2 NWs was just ˜2.0 nm. Moreover, Pt-CeO2 NW@SiO2 showed significantly enhanced catalytic performances for total oxidation of CO and toluene. The increased catalytic properties are attributed to the strong metal-support interaction effect between Pt and CeO2 NWs at sub-nanoscale. Most importantly, the special core-shell structure also affords excellent sintering resistance retention up to 700 °C for 100 h, due to the guarding effect of porous silica shell. Finally, the formation mechanism of Pt-CeO2 NW@SiO2 was investigated in detail. Current strategy should inspire many rational designs of rare-earth metal-based nanocatalysts for real-world catalysts.