#photoelectron spectroscopy

[electricalinsightsdaily]

Work Function: Unlocking the Secrets of Electron Emission

The work function is a fundamental concept in solid-state physics and materials science, playing a crucial role in understanding electron emission from surfaces. This intrinsic property of materials describes the minimum energy required to extract an electron from a solid to a point immediately outside its surface.

At its core, the work function represents the energy barrier that electrons must overcome to escape the material. This barrier arises from the attractive forces between the electrons and the positive ions in the material's lattice structure. The strength of this barrier varies among different materials, leading to diverse applications in technology and research.

The derivation of the work function involves considering the energy states of electrons within the material and at its surface. We start by examining the Fermi level, which represents the highest occupied energy state at absolute zero temperature. The work function is then defined as the energy difference between the Fermi level and the vacuum level (the energy of a free electron at rest outside the material).

To calculate the work function, we must account for several factors:

The chemical potential of electrons in the bulk material

The electrostatic potential difference between the bulk and the surface

Surface dipole effects due to electron redistribution at the material's boundary

By combining these components, we arrive at a comprehensive understanding of the work function and its variations across different materials and surface conditions.

The implications of work function extend far beyond theoretical physics. It influences various phenomena and technologies, including:

Thermionic emission in vacuum tubes and cathode ray tubes

Photoelectric effect in solar cells and photomultiplier tubes

Field emission in electron microscopy and flat-panel displays

Schottky barriers in semiconductor devices

Read More about work function formula

[whats-in-a-sentence]

The investigators deposited atomically precise nanoribbons of graphene sheets in a chevron pattern onto a gold surface, as shown in figures 4.18a, b and used XPS to ensure that the graphene did not suffer any oxidation during this process. As shown in figure 4.18c, the carbon 1s peak has a chemical bonding environment characteristic of the absence of oxygen.

"Chemistry" 2e - Blackman, A., Bottle, S., Schmid, S., Mocerino, M., Wille, U.

[lottiecrabie]

Morning sex with pfms Matty 😇

I know you are not taking blurb requests but I would really really love it if you wrote one about pfms matty taking care of reader during exam season because I know she is a studious gal. “Study dress babe? Let me ✨alleviate it✨” “you’ve been working so hard” all that,,, can you tell that I’m reader 😁😁 If I pass I’ll credit u for sure

i think it’s too late to help you pass but still

she bites at her nails, flicks her eyes between her books and her notes, desperately tries to understand the complex science jargon she’s dutifully transcribed without getting. there’s pink, square letters on the lines; a collection of bulletpoints and highlights and pretty drawings. it’s unintelligible to her.

worry starts to rise in her chest. she feels it near her heart, beating alongside it, racing it. tears prickle at her eyes as she bites her finger beds raw, chews at the skin until it tastes metallic. she swears, wiping away the blood, moaning in pain.

a knock on the window. she stands, opening it to find matty grinning at her. he dips in and gives her a sweet kiss.

‘we can’t see each other today.’ she shakes her head as matty steps inside her room. ‘i have an exam coming up. i need to study.’

‘it’s saturday,’ matty says, like she was a bit silly. ‘live a little.’

again, she shakes her head. ‘i’m really not getting it. it’s— shit, it’s actually hard.’ she gives him a warning look, silently stopping him from saying whatever stupid quip he’s thinking.

‘you sound stressed,’ matty says, frowning.

‘i am.’

‘how about i help with that?’ a faint, cheeky smile shines on his face, hidden under the guise of seriousness. she gives him a look, unimpressed. ‘i meant studying,’ matty raises both his hands innocently.

‘sure you did.’

‘c’mon, let me see,’ matty sits at her desk, peering over her notes. ‘ouch.’

‘yeah.’ a small, pained moan comes from the back of her throat. she falls over her bed quite dramatically, spreading her arms in abandon. ‘my parents will kill me.’

‘they won’t,’ matty waves away, flipping a page.

‘no, they will. quite brutally, even. is the iron maiden still legal?’

‘god, you’re dark,’ matty says almost proudly. ‘and they won’t kill you because you won’t fail. alright. why can the ionization of atoms occur during photoelectron spectroscopy, even though ionization is not a thermodynamically favored process?’ matty looks up at her. ‘oh, we will be here all night.’

and they are, falling asleep clutching flash cards and notes, chemistry elements slack on their tongues. they wake up fully dressed, over the sheets, awkwardly tucked around each other.

she blinks awake, blushing as she notices matty. it’s the first time he’s fallen asleep here, and it’s not even for a dirty reason. there’s a strange feeling coming with that idea. she unwraps her arms around his middle, freeing him, taking her head off his shoulder.

matty makes a small, tired noise. ‘i feel my hand again,’ he says, moving his fingers.

‘you could have moved me,’ she accuses, now feeling terrible for his discomfort.

‘nah. i liked having you close.’ matty rolls on his side, watching her with a smile. ‘you’re cute when you sleep.’

‘oh, god. i hope i didn’t drool.’

‘just a little.’

‘matty!’ she whines. she shoves her face into her palms with a shamed groan.

‘what? i’ve seen worse.’ he tugs at her hand, coaxing her out.

she emerges from them still vaguely embarrassed. ‘thank you for helping me study,’ she whispers.

‘you’re welcome.’ he kisses her cheek, then the other, bending away just enough to stare at her. his eyes dip to her parted lips. ‘now can i help you the other way?’

she reddens, a low thrum of excitement coming up her spine. ‘yes,’ she breathes, looking away bashfully.

matty grins widely. he makes to catch her lips, but she turns her head. ‘morning breath,’ she explains. he shakes his head, but kisses down her neck instead.

matty rolls her on her back, uncovering her evening clothes one by one. she breathes quicker, watching him, trying to make even less noise. her parents are right next door, surely awake.

he licks down her belly, flipping her skirt, before sucking on her clit through her underwear. she jumps, spreading her legs wider, tugging at her own panties to try taking them off. matty listens, laughing as he drags them off her thighs, coming back happy.

he zigzags across her wet core, just missing the parts where she wants him the most. his hands keep her in place, teasing her until she’s dripping on the sheets.

‘matty,’ she whispers. ‘please.’

‘so polite,’ matty taunts, though gives in to her still.

his lips wrap around her bud and he sucks, flicking it a few times. his fingers thrust into her. he follows the familiar, known rhythm, one that has her kicking in bed and tugging vengefully at his hair in no time. she slaps one hand over her mouth, breathing twice as hard to compensate.

pleasure razes through her, hot, white euphoria waving building inside her belly. she feels an indescribable heat. her sweaty hair sticks to her forehead in answer.

pressure grows inside of her, tightening and tightening until she’s so tense she could crack.

she whispers his name, though it’s smothered by her palm. matty seems to hear it still, garbled and muffled, and he licks her with twice the devotion.

sunlight shines on her naked breasts. she pants, giggling to herself, always in disbelief that she’s almost coming until she’s there, she’s right—

‘honey,’ her father knocks at her door. she jumps, opening her eyes wide. ‘are you getting ready? we leave for church soon.’

‘oh, um—‘ matty fucks his fingers faster. ‘yeah, i’m almost there—‘ she bites back a scream, rolling her eyes.

‘ok. we’ll wait for you downstairs.’

as soon as his steps disappear down the hallway, she finally breaks, coming with a killed cry. the tight strings snap and delicious relief spreads through her, relaxing each limb until she’s slack on her bones. she grins loosely, feeling her head sing.

matty kisses her bud, coming up her body with a grin. ‘you’ve got church,’ he says, cheeky.

‘i do.’ she cups both his cheeks, still shortwinded. ‘will i see you there?’

‘if i can’t help it,’ matty sighs dramatically.

she gives him a small, teasing smirk. ‘maybe i can return the favor there.’

he is suddenly deadly serious. ‘i will be there.’

she giggles, giving him a small smack of lips, pushing him away when he tries to part his mouth. ‘morning breath,’ she reminds him.

already dressed from a fitful sleep, matty puts on his shoes and opens the window. she sits in bed, truly loose and relaxed. ‘thanks for the help,’ she smiles.

he throws a leg over the window sill. he winks. ‘any time.’

[materialsscienceandengineering]

Neutralizing electronic inhomogeneity in cleaved bulk MoS₂

Molybdenum disulfide (MoS2) is a highly versatile material that can function, for example, as a gas sensor or as a photocatalyst in green hydrogen production. Although the understanding of a material usually starts from investigating its bulk crystalline form, for MoS2 much more studies have been devoted to mono and few layer nanosheets. The few studies conducted thus far show diverse and irreproducible results for the electronic properties of cleaved bulk MoS2 surfaces, highlighting the need for a more systematic study. Dr. Erika Giangrisostomi and her team at HZB carried out such a systematic study at the LowDosePES end-station of the BESSY II light source. They utilized X-ray photoelectron spectroscopy technique to map the core-level electron energies across extensive surface areas of MoS2 samples. Using this method, they were able to monitor the changes in the surface electronic properties after in-situ ultra-high-vacuum cleaving, annealing and exposure to atomic and molecular hydrogen.

Read more.

[waquasuniverse]

X-ray Photoelectron Spectroscopy Market To Reach $948.9Mn By 2030

The global XPS market is expected to reach USD 948.9 million by 2030, registering a CAGR of 3.9% from 2024 to 2030, according to a new report by Grand View Research, Inc. Growing application of XPS technology in different industries such as healthcare, semiconductors, aerospace, automotive, and electronics along with rising demand for research and development across all these industries is…

[edgetechindutries]

The difference between 3mol/5mol/8mol yttria-stabilized zirconia ceramics

Zirconium oxide is a widely used ceramic material. It has three phases with different structures, namely the monoclinic phase, tetragonal phase, and cubic phase. Different phase contents can have a greater influence on the performance of zirconia ceramic materials. At present, the most common yttrium-stabilized zirconia materials are yttrium-stabilized zirconia materials. Among them, 3Y-TZP (3% (molar fraction) Y2O3) material has the best mechanical properties. It is also the most commonly used type of zirconia ceramic material current and has broad application prospects in different industries, such as the chemical industry, machinery, etc. The performance of 3Y-TZP prepared by the different methods is quite different. To obtain zirconia ceramic materials with higher mechanical properties, the sintering temperature can be controlled, doped, etc. Adding additives can also change the grain size and phase composition of the material to a certain extent. The grain size and phase composition will have a significant effect on the physical properties of ceramic materials, so studying the influence of grain morphology and phase composition on ceramic materials is of great significance in exploring the overall improvement of the performance of zirconia materials.

1. Effect of yttrium content on relative density

The molar fraction of yttrium oxide corresponding to the maximum densification is 3%, and the relative density reaches 98.113%. Before the critical point, with the increase of yttrium oxide content, the density of the sample gradually increases and then gradually decreases after the boundary point. The relative density of the sintered body with a molar fraction of yttrium oxide of 3% is greater than that of other groups, indicating that Y2O3 can promote the densification of zirconia during sintering. This is because the radius of Y3+ (1.06A) is larger than the radius of Zr4+ (0.87A). When Y2O3 forms a substitutional solid solution with ZrO2, the lattice of the main crystal phase of ZrO2 is distorted, the defects increase, and it is convenient for the structural unit to move and promote sintering, thereby obtaining a higher density. When the yttrium oxide content exceeds the critical value, the role of Y2O3 in the zirconia matrix is ​​weakened, and excessive Y2O3 hinders the crystallization of zirconia during sintering, so the relative density gradually decreases. In addition, X-ray photoelectron spectroscopy (XPS) analysis shows that Y3+ is concentrated at the grain boundary, which will strongly hinder the movement of the grain boundary, prevent or delay the separation of pores from the grain boundary so that the densification process can continue in the later stage of sintering. When the yttrium oxide content is 3% (molar fraction), this effect is maximized. Therefore, at around 3% (molar fraction), the density of zirconia ceramic material reaches the maximum.

2. Effect of yttrium oxide content on mechanical properties of zirconia ceramics

With the increase of yttrium oxide molar fraction, the bending strength of zirconia ceramics increases rapidly, and the maximum strength value is obtained at a yttrium oxide content of 3% (molar fraction). When the yttrium oxide content is increased, the strength value no longer increases but gradually decreases.

With the increase of yttrium molar fraction, the hardness of zirconia ceramic material increases, and the hardness of the material reaches the maximum value at 3%. Then, with the increase of yttrium content, the hardness of zirconia gradually decreases.

When the yttrium content is 3% (molar fraction), the particle size of yttrium-stabilized zirconia is the smallest, and zirconia has a higher density. When the molar fraction of yttrium is 3%, a certain amount of elongated crystals appear in the microstructure of zirconia. The long crystals act as solidification bridges between the tiny zirconia particles and the bulk, which makes the zirconia material more tightly bonded and obtains a higher bonding strength. This is why the ceramic has a higher hardness when the yttrium content is 3%.

[realdrake]

Sustainable Biopolymer Membranes for Organic Solvent Nanofiltration: A Breakthrough in Green Technology

The increasing demand for sustainable alternatives to fossil-bas…

The increasing demand for sustainable alternatives to fossil-based polymer materials has led to the development of innovative biopolymer membranes for organic solvent nanofiltration (OSN). In a recent study, researchers have successfully fabricated interpenetrating biopolymer network (IPN) membranes from natural compounds, agarose and natural rubber latex, without the use of toxic cross-linking agents. This breakthrough technology offers a promising solution for the separation of molecular species in harsh organic media, benefiting various industries such as petrochemical, biorefining, paint, pharmaceutical, and food.

Key Features of the Biopolymer Membranes

The biopolymer membranes exhibit excellent solvent resistance and tunable molecular sieving, making them suitable for a wide range of applications. The membranes are biodegradable, ensuring an environmentally friendly end-of-life phase. The use of natural materials and water as a solvent during fabrication reduces the environmental impact of the production process. Additionally, the membranes demonstrate high mechanical strength, thermal stability, and resistance to fouling, making them suitable for long-term operation in harsh environments.

Fabrication and Characterization of the Membranes

The IPN membranes were fabricated by combining agarose and natural rubber latex through a self-assembly and self-cross-linking process. The morphology and chemical information of the membranes were characterized using various techniques, including scanning electron microscopy (SEM), atomic force microscopy (AFM), and nano-Fourier transform infrared (nano-FTIR) spectroscopy. The results revealed a textured dense microstructure with a water contact angle of 71° ± 1° and a roughness value of 138.75 nm. The membranes' surface chemistry was also analyzed using X-ray photoelectron spectroscopy (XPS), which showed a high concentration of hydroxyl and carboxyl groups, contributing to their hydrophilic nature.

Nanofiltration Performance and Biodegradability

The nanofiltration performance of the membranes was evaluated using a crossflow filtration system. The results showed a linear correlation between the pure solvent flux and the solubility parameter, indicating that the membranes can be used with optimum linear control over polar solvents. The membranes demonstrated long-term stability over 72 h of continuous crossflow nanofiltration at 20 bar. The biodegradability of the membranes was confirmed through enzymatic treatment, ensuring a sustainable end-of-life phase. The membranes' biodegradability was further evaluated using a soil burial test, which showed a significant reduction in membrane weight and molecular weight over a period of 6 months.

API Purification and Impurity Removal

The membranes were successfully used for the purification of an active pharmaceutical ingredient (API) and the removal of a carcinogenic impurity. The results showed that the membranes can effectively remove impurities below the threshold of toxicological concern, making them suitable for pharmaceutical applications. The membranes' ability to remove impurities was further evaluated using a range of analytical techniques, including high-performance liquid chromatography (HPLC) and mass spectrometry (MS).

Scalability and Industrial Applications

The scalability of the membrane fabrication process was evaluated using a pilot-scale setup. The results showed that the membranes can be fabricated on a large scale while maintaining their performance and properties. The membranes' potential for industrial applications was further evaluated through collaborations with industry partners, which showed promising results in the areas of petrochemical, biorefining, and pharmaceuticals.

The development of biopolymer membranes for OSN offers a sustainable solution for the separation of molecular species in harsh organic media. The use of natural materials, water as a solvent, and the biodegradability of the membranes reduce the environmental impact of the production process. The membranes' excellent solvent resistance, tunable molecular sieving, and long-term stability make them suitable for various industrial applications. This breakthrough technology has the potential to replace traditional fossil-based polymer materials, contributing to a more sustainable future.

[nidarsanafwr]

https://social.studentb.eu/read-blog/174753_x-ray-photoelectron-spectroscopy-market-size-overview-share-and-forecast-2031.html

X-ray photoelectron spectroscopy Market Size, Overview, Share and Forecast 2031

[dangerdust2]

Exposure to silica dust is one of the oldest known causes of pulmonary diseases, and is associated with a variety of occupations, such as construction, quarrying, and chemical industries.

While the inhalation of fine silica particles is a well-recognized risk factor for silicosis, several studies have reported an association between silica exposure and sarcoidosis or sarcoid-like granulomatous lung diseases.

According to the literature, silica exposure may also be a trigger for other conditions, including hypersensitivity pneumonitis (HP), lung cancer, tuberculosis, chronic obstructive pulmonary disease, and kidney disease.

A 44-year-old woman was admitted to hospital with end-stage renal failure, productive cough, and decreased exercise tolerance. She had owned nine cats, which resulted in long-term exposure (18 years) to silica-containing bentonite cat litter. 

X-ray photoelectron spectroscopy revealed the presence of silicon in the lung biopsy specimen, as well as in the patient’s cat litter.

The pulmonary condition was suggestive of sarcoid-like lung disease, rather than silicosis, sarcoidosis, or hypersensitivity pneumonitis, according to the clinicopathological findings.

Renal failure appeared to be a result of chronic hypercalcemia due to extrarenal calcitriol overproduction in activated alveolar macrophages.

Ultimately, the patient was diagnosed with sarcoid-like lung disease complicated by end-stage renal failure from exposure to bentonite cat litter.

We believe that our patient’s disease was a result of the chronic inhalation of bentonite dust, as we excluded other possible causes and observed a significant improvement after the causative agent had been removed.

[carbon-black-deri]

How is carbon black measured?

Carbon black is a versatile material used in a variety of industries, including rubber, plastics, coatings, inks, and more. To ensure its quality and suitability for specific applications, carbon black is measured using various parameters and techniques. In this article, we will take an in-depth look at the different methods used for carbon black measurement and provide a comprehensive guide to understanding this important aspect of carbon black analysis.

Particle size distribution:

One of the key measurements of carbon black is its particle size distribution. Particle size affects the performance and behavior of materials in different applications. There are various techniques for measuring particle size, such as laser diffraction, sedimentation, and microscopy. Laser diffraction is a popular method that uses scattered light to determine size distribution, while sedimentation involves measuring the sedimentation rate of particles. Microscopy allows detailed examination at the level of individual particles.

Specific surface area:

The surface area of carbon black significantly affects its properties, such as its ability to adsorb species, interact with other materials, and provide reinforcement. Traditionally, the BET (Brunauer-Emmett-Teller) method is used to measure specific surface area. The technique involves the adsorption of gas molecules onto the surface of carbon black and determining the amount of gas adsorbed. The higher the specific surface area, the more effective the carbon black is in many applications.

Structural and surface chemistry:

The structure and surface chemistry of carbon black play a crucial role in determining its performance. Morphological characteristics, such as aggregate size, shape and porosity, affect the dispersion and reinforcing capabilities of carbon black. Techniques such as transmission electron microscopy (TEM) and scanning electron microscopy (SEM) provide valuable insights into the structure and morphology of carbon black particles. Surface chemistry can be analyzed by techniques such as X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR), which help identify the functional groups and surface features of carbon black.

Tint Strength and Chroma:

Tinting strength refers to the ability of carbon black to impart color or hue to a material. It is an important parameter for the ink, plastics and coatings industries. Tinting intensity can be measured by comparing the color intensity of a sample mixed with a standard reference material. Colorimetry is a precise method that uses color parameters such as Lab* values or CIE (International Commission on Illumination) color space coordinates to quantify the color properties of carbon black. These measurements are critical to maintaining consistency and meeting color specifications for various applications.

Rheological properties:

The rheological properties of carbon black, such as viscosity and flow behavior, are critical to its processing properties in the rubber and polymer industries. The Mooney viscosity test is commonly used to measure the viscosity of rubber compounds filled with carbon black. In addition, dynamic mechanical analysis (DMA) and rotational viscometry help determine the effect of carbon black on the viscoelastic behavior of the material.

Accurate measurement and characterization of carbon black is critical to ensuring its quality, performance and suitability for specific applications. Particle size distribution, specific surface area, structure and surface chemistry, tinting strength and rheological properties are key parameters used to measure and analyze carbon black. These measurements enable manufacturers and end users to select the appropriate carbon black grade based on their desired results.

If you want to know about high-quality carbon black products, please contact DERY for more information!

[studentbyday]

photoelectron spectroscopy (PES)

PES uses the photoelectron effect which is basically describing how, when you zap a sample with photons of electromagnetic radiation (energy), you remove/eject its electrons. This uses the concept of ionization energy. Radiation = ionization energy + some extra. You're giving the sample enough energy to remove its electrons (ionization energy) and the extra energy gives the electron enough energy to move (kinetic energy). The electron's ionization energy is also called binding energy (because...???).

This is another way to say it: energy of photon = binding energy + kinetic energy of electron. Or abbreviated, Ephoton = BE + KEelectron

If you want to break it down further, energy of photon = Planck's constant*frequency of photon in Hertz = BE + KEelectron, or abbreviated: hv = BE + KEelectron

Solving for BE, that's BE = hv - KEelectron

PES creates a graph showing the number of electrons ejected on the y-axis vs their binding energy in electron volts eVeVstart text, e, V, end text) or megajoules (MJMJstart text, M, J, end text) per mole.onn the x-axis. How does it create this graph?

High-energy photons, usually UV or X rays, hit a sample of free atoms or molecules (the photoelectric effect was originally described for metal surfaces but it also applies to free atoms or molecules), ejecting their electrons. These electrons' kinetic energies are measured with an energy analyser. A detector then counts how many electrons of a certain kinetic energy there are. From there, we can calculate the binding energies for the electrons ejected (called photoelectrons) using the equation above. Since the energy in the photons is constant for all electrons ejected, the greater the electron's kinetic energy, the less their binding energy, and vice versa.

[juniperpublishersmaterialscience]

Hydrothermal Synthesis of Co3O4 Urchin-Like and their Catalytic Properties in Co Oxidation

Authored by: Gunel Imanova

Abstract

Urchin-like nanocrystalline Co3O4 has been success fully prepared through a hydrothermal synthesis route via a simple and elegant route at low temperature, and was characterized by thermal analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, nitrogen adsorption/desorption isotherms and X-ray photoelectron spectroscopy (XPS). The light-off temperature (10% conversion) of CO oxidation on Co3O4 ursin-like catalyst was at 60°C and when the temperature reaches 120°C, the CO conversion ratio reaches 100%. The high relative concentration surface-adsorbed oxygen on the Co3O4 ursin-like is highly active in CO oxidation reaction due to its higher mobility than lattice oxygen. The study it has been shown that the high catalytic activity and stability for CO oxidation can be attributed to its higher mobility than lattice oxygen. In addition, the oxide defects can adsorb and activate gaseous O2 to form active oxygen species, which is beneficial to promote the CO oxidation reaction. The as-obtained results make the Co3O4 nanomaterial possible candidate to be used as catalyst for CO oxidation.

Keywords: Hydrothermal Synthesis; Urchin-Like; Nanocrystalline Co3O4; Catalytic Properties; Oxidation

Abbreviations: TGA: Thermal Analysis; XRD: X-ray Diffraction; SEM: Scanning Electron Microscopy; XPS: X-ray Photoelectron Spectroscopy; CO: Carbone monoxide; TCD: Thermal Conductivity Detector; BET: Brunauer-Emmett-Teller

Introduction

Carbone monoxide (CO), emission from mobile and stationary combustion sources is harmful to the environment, one of the major air pollutants and its presence even in traces may cause serious environmental and health problems. Therefore, the elimination of CO became important, and the oxidation of CO is a promising route to cleaning the air and lowering automotive emissions. Tricobalttetraoxide (Co3O4), a typical spinel-structure transition metal oxide, shows a strong morphology-dependence in the chemical reactions such as CO oxidation [1-6], CH4combustion [7], and selective reduction of NO with NH3 [8]. For example, in 2009, it has been developed Co3O4 nanorods containing substantial amounts of exposed (110) planes exhibited superior catalytic activity for low-temperature CO oxidation to the spherical particles mainly enclosed by the (111) facets [1]. Also, Co3O4 nanotubes [9], nanosheets [3], nanowires [4], and nanocubes [10] similarly showed a distinct shape effect in CO oxidation. These results clearly confirm that controlling the morphology of nanostructured cobalt oxides is beneficial to expose more catalytically active sites.

Development of catalysts with desirable dimensions andmorphology is an interesting and challenging task owing to their improved catalytic activity and increasing applications in various fields [11-13]. Hierarchical 3D urchin-like nanostructures are promising for wastewater treatment through heterogeneous photo-catalysis because of their high surface area which facilitates catalysis by providing a larger solid-liquid interface. As can be seen from the writing information, radiation-heterogeneous forms in contact of to begin with radiation-oxidative treated zirconium and nano-zirconium oxide with water causes a alter within the sum of surface oxide film. The arrangement of an oxide film, in turn, changes the radiation-catalytic movement and physicochemical properties, which influence the dynamic parameters. One of them, the foremost delicate is the electro physical and optical properties of metal surfaces [14-22].

In this study, we report on the hydrothermal synthesis and physicochemical characterization of urchin-like nanostructures of Co3O4 with a surface area of 43m2/g and their application in the CO reaction. The nanomaterial was synthesized using PEG-400 as a template. The Co3O4 morphology proved to be stable and did not collapse after calcination at 300°C for 2h. XRD measurements showed that the Co3O4 average particle size is 44nm. The assynthesized C Co3O4 ursin-like exhibited superior catalytic activity and durability in CO oxidation at room temperature. It has been shown that when the temperature reaches to 120°C, the CO conversion ratio reaches 100%.

Experimental Details

Hydrothermal synthesis

The Co3O4 were synthesized by the typical procedures reported in the literature [23]. 0.77 mmol of CoCl2.6H2O was dissolved in distilled water (27mL), followed by the addition of 0.25 mmol of PEG-400 then 8 mL of H2O2 (30%). The solution was transferred into a Teflon-lined stainless-steel autoclave which was sealed and maintained at 100°C for 12h. The autoclave was then cooled to 25°C, 2.25 mmol of urea was added and the autoclave was heated at 150°C for 16h. The precipitate was filtered, washed several times with deionized water and ethanol until free of chloride ions (AgNO3 test) and dried overnight at 80°C under vacuum. Then, it was calcined in air at 300°C for 2h.

Characterization

TGA was performed using a Setaramsetsys 1750 apparatus at a heating rate of 2°C/min from RT to 700°C. XRD data were collected on a Panalytical X’Pert Pro diffractometer with CuK α radiation (λ = 1.5406 Å) and a graphite monochromator by applying a step scanning method (2θ range from 10 to 70°). Raman spectroscopy was performed using a Jobin-Yvon T64000 spectrometer with a laser wavelength of 785 nm and a laser power of 3m W and taken after 60 seconds of exposure. The morphology of the sample was studied using an FEI Quanta 200 Environmental SEM and H2-TPR profiles were obtained on a Micromeritics Autochem analyzer, in a Pyrex U-tube reactor and an on-line thermal conductivity detector (TCD). The calcined sample (50 mg) was first purged with an argon flow of 20 mL/min at a ramp rate of 10 °C/min to 350°C for 30 min to remove the traces of water, followed by cooling to room temperature. Then the sample was reduced by 4% vol. hydrogen and argon mixture (30 mL/min) at a temperature ramp rate of 5°C/min. The effluent gas was passed through a cooling trap to condense and collect the water produced during the reductions. The Brunauer-Emmett-Teller (BET) specific surface area, average pore diameter and pore size distributions were determined by N2- physisorption at 77K using a Micrometrics ASAP-2020 instrument.

Catalytic investigation

CO oxidation was tested in a flow reactor. Before the reactions, Co3O4 was activated at 300°C for 1h at 5%O2/He. After the sample was cooled down to room temperature, a feed gas (1%CO/20%O2/ He) was passed over the catalyst with a flow rate of 30 mL/min. 50 mg of the catalyst was heated to the desired reaction temperature and then kept for 1 hour until the catalyst reaction reached a steady state. The amounts of CO, CO2 and O2 in the inlet and outlet streams were analyzed by an online gas chromatograph. CO conversion was calculated from the measured CO concentration using the formula CO conversion = [(Coin - COout)/COin], where COin and COout were the inlet and outlet CO concentration, respectively.

Result and Discussion

Thermo gravimetric analysis (TGA)

The thermal behavior of the hydrothermally as-prepared sample was examined using TGA in order to determine the appropriate calcination temperature. As depicted in Figure 1, a sharp decrease with a total weight loss of 11.2% around 260°C which indicated that a temperature of 300°C was chosen to completely decompose of cobalt chloride carbonate hydroxide hydrate decomposed completely into Co3O4, CO2, Cl2 and H2O.

X-ray diffraction (XRD)

The diffraction patterns (XRD) are given in Figure 2. All the diffraction peaks displayed in the diffractogram (a) can be perfectly indexed to the cobalt chloride carbonate hydroxide hydrate [JCPDS 00-038-0547, Co (CO3)0.35Cl0.20(OH)1.10.1.74H2O] and those in (b) with cobalt oxide [JCPDS 01-076-1802, Co3O4]. The second XRD pattern shows that the main peaks of the final products could be indexed to a cubic phase cobalt oxide and no peaks of other phases are observed. All the peaks can be indexed to the diffraction from the (111), (220), (311), (222), (400), (422), (511) and (440) planes of cubic Co3O4, respectively. Crystallite sizes (DXRD) for Co3O4 after heating in air at 300°C was estimated from the broadening of the most intense XRD peak (311) using the Debye-Scherrer approximation [24]. The average particle size of Co3O4 catalyst was calculated to be 44nm.

Raman spectroscopy

Raman spectroscopy of Co3O4 nanostructure is displayed in Figure 3. The Raman spectrum of the Co3O4 in the range of 100- 800 cm-1 shows five obvious peaks (A1g + Eg + 3F2g) located at around 187, 495, 505, 597 and 658 cm-1, corresponding to the five Raman-active modes of Co3O4. The peak at 187 cm-1 is attributed to the F(3)2g mode of tetrahedral sites (CoO4). The peaks at 459 and 505 cm-1 are assigned to the Eg and F(2) 2g symmetry, respectively. Whereas the peak at 597cm-1 is attributed to the F(1)2g symmetry. The strong band at 658 cm-1 with A1g symmetry is attributed to the characteristics of octahedral CoO6 sites corresponding to the unique characteristics of spinel-type cubic Co3O4 phase [25,26] and no additional peaks assigned to other impurities such as Co2O3 and CoO have been found in good agreement with the XRD result. The Raman shifts are consistent with those of pure crystalline Co3O4, indicating that the Co3O4 catalyst has a similar crystal structure of the bulk Co3O4.

Scanning electronic microscopy (SEM)

Figures 4a & 4b shows the SEM images of the as-prepared precursor obtained by hydrothermal treatment at 150°C and after calcination at 300°C. As shown in Figure 4b, The Co3O4 morphology proved to be stable and did not collapse after calcination at 300°C in air for 2h. Polyethylene glycol (PEG) was used as a surfactant, which can modify the surface energy of the crystallographic surface. Co3O4 has a uniform urchin-like structure covered with dense nanowires starting from the center with an average of diameter of 4-6μm. The nanowires appear to have a common center and grow to the outside along the radial direction.

H2-TPR studies

nostructures, TPR measurements were carried out and shown in Figure 5. The H2-TPR profile of the catalyst shows two main reduction peaks at about 360°C and 440°C, which can be attributed to the reduction of Co3O4 into CoO and from CoO to metallic Co [27], respectively. The narrow peaks indicate the reduction process was fast. The curve exhibits Co3+ is reduced at first, and then the produced Co2+ and Co2+ in the catalyst itself are further reduced into metallic Co.

Nitrogen adsorption-desorption

As shown in Figure 6, The N2 adsorption-desorption isotherms at 77 K which is close to type IV of the IUPAC classification [28] with an evident hysteresis loop in the 0.5 to 1.0 range suggesting that the Co3O4 ursin-like is basically mesoporous.

The specific area of the sample calculated by BET to be 43m2/g and the average pore diameters is 16 nm. These porous structures can be helpful for CO molecules to rapidly penetrate into the pores and contact to active sites during the catalytic process [29,30].

X-ray photoelectron spectroscopy (XPS)

XPS analysis was employed to investigate the surface elemental composition and chemical state of the as-obtained Co3O4-ursin like a catalyst, as shown in Figure 7. The XPS survey spectrum (Figure 7a) reveals that the sample only consists of cobalt and oxygen (the C1s peak was appeared, which could be due to the support used to prepare a sample for XPS analysis).The Co2p spectra in Figure 7b exhibited two major peaks with binding energies at around 780.0 eV and 795.1 eV corresponding to the Co2p3/2 and Co2p1/2, respectively, suggesting that the cobalt oxide was present in the form of Co3O4 [31,32].

Next, Co2p3/2 peaks in Figures 7b & 7c were fitted and de convoluted into two peaks of 780.8 and 779.5 eV, which are attributed to Co2+ and Co3+ respectively. As shown in Figure 7d, the O 1s electronic levels also were examined. The asymmetric O 1s could be de convoluted to two components at 531.5 and 529.5 eV. The XPS peak at 529.5 eV was attributed to the surface lattice oxygen (Olatt) species, and the 531.5 eV peak was ascribed to the surface adsorbed oxygen (Oads) species in Co3O4 [33,34]. The O1s peak at 531.5 eV in the spectrum indicates the presence of surface adsorbed oxygen such as O22- or O-, belonging to defect-oxide or hydroxyl-like group [35,36]. The presence of surface hydroxyl like groups can result from oxygen vacancy on the surface of the Co3O4 catalyst originating from the dissociative adsorption of H2O molecules. The oxide defects can adsorb and activate gaseous O2 to form active oxygen species, which is beneficial to promote the oxidation reaction. Furthermore, Co3O4 ursin-like had the Oads/ Olatt ratio about 1.7 proving that its surface possesses the largest amount of facile and reactive oxygen species, which is beneficial to promote the CO oxidation reaction [37].

Catalytic properties of Co3O4 ursin-like in CO oxidation

As a typical probe reaction of numerous novel catalytic materials, CO oxidation was carried out to evaluate the catalytic activity of the as-prepared Co3O4 ursin-like. As shown in Figure 8a, the light-off temperature (10% conversion rate) at 60°C and when the temperature reaches to 120°C, the CO conversion ratio reaches 100%, which exhibits higher catalytic activity than that of the Co3O4 nanowires [4] and Co3O4 nanorods [38]. The longterm stability of the catalyst is important in practical applications. Furthermore, the stability test for CO oxidation was performed over the period of 20 h at T=120°C, as shown in Figure 8b. The high catalytic activity and stability for CO oxidation can be attributed to its higher mobility than lattice oxygen. In addition, the oxide defects can adsorb and activate gaseous O22 to form active oxygen species, which is beneficial to promote the CO oxidation reaction.

Scanning electronic microscopy of the spent catalyst

As shown in Figure 9, the morphology of the spent catalyst after 20 h on stream reaction still retains ursin-like shape.

It can be shown that excellent catalytic performance and long-term stability for CO oxidation make the Co3O4 nanomaterial possible candidate to be used as a catalyst for CO oxidation.

Conclusion

In this paper, we have obtained Co3O4 precursor by a lowtemperature hydrothermal method. The product Co3O4 has a uniform urchin-like structure covered with dense nanowires starting from the center with an average of diameter of 4-6 μm by PEG-400 as a template. The light-off temperature (10% conversion) of CO oxidation on Co3O4 ursin-like catalyst was at 60°C and when the temperature reaches to 120°C, the CO conversion ratio reaches 100%. The stability test for CO oxidation was performed over the period of 20h at T = 120°C. It has been shown that the high catalytic activity and stability for CO oxidation can be attributed to its higher mobility than lattice oxygen. In addition, the oxide defects can adsorb and activate gaseous O2 to form active oxygen species, which is beneficial to promote the CO oxidation reaction. The as-obtained results make the Co3O4 nanomaterial possible candidate to be used as catalyst for CO oxidation.

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