Adsorption Of Oxygen Molecules Research Articles

Nanocrystalline and mesoporous (Ba,Sr)(Sn,Mn)O3 perovskite solid solution: a potential n-type semiconductor for room temperature ethanol sensing applications

EtOH oxidation at ∼55% humidity over Ba0.98Sr0.02Sn0.95Mn0.05O3 is enhanced. The electrons from Ba0.98Sr0.02Sn0.95Mn0.05O3 interact with the adsorbed oxygen molecules, forming adsorbed oxygen species which interact with ethanol to give CO2 and H2O.

Enhanced electrochemical oxygen reduction reaction on “C–O–Si” bonds in Si-doped graphene-like carbon

The use of heteroatom-doped carbon materials as non-precious metal catalysts for oxygen reduction reactions has attracted much attention from researchers. This paper presents the synthesis of two-dimensional Si-doped graphene-like materials (Si-GLC) featuring “C–O–Si” bonds through an in-situ doping method. Since the electronegativity of the Si (1.90) is much smaller than that of C (2.55) and O (3.44), the formation of the “C–O–Si” bond causes Si to lose a large number of electrons and become positively charged. This increases the adsorption of electronegative oxygen, thereby improving the activity of oxygen reduction reactions. The adsorption energy of oxygen molecules on Si-GLC was calculated to be −3.57 eV using density functional theory, much lower than on GLC (−2.18 eV). This suggests that Si doping enhances the adsorption of oxygen molecules by graphene-like materials, which is crucial for improving the performance of oxygen reduction reaction. Si-GLC displayed a half-wave potential of 0.80 V (vs. RHE) and a diffusion-limited current density of 5.81 mA cm−2 in 0.1 M KOH solution, demonstrating excellent catalytic activity for oxygen reduction reaction. It also exhibits good stability and tolerance to methanol crossover effect. In-situ doping creates “C–O–Si” bonds, modulating charge density and providing a strategy for high-performance oxygen reduction catalysts.

Estimation of the Active Surface Area on the Pt Catalyst during ORR Proceeds with the in-Situ XAFS Method

Electrocatalysts for polymer electrolyte fuel cells must be not only highly active and durable but also have a high Pt utilization rate to suppress their cost. Pt utilization is evaluated using the electrochemically active surface area (ECSA). However, ECSA is calculated from the electric charge required for the hydrogen adsorption as the Pt surface area, and it does not accurately reflect the three-phase interface where the oxygen reduction reaction (ORR) occurs. Additionally, it is impossible to estimate ECSA from the electrochemical measurements data progressing the ORR because the reduction current is dominant. Therefore, we focused on in-situ X-ray absorption fine structure (XAFS) measurements using hard X-rays as a new estimation method for the real active surface area of the electrocatalyst during ORR. Concretely, the height variation of the white line of the XANES spectrum, which corresponds to the valence changes from Pt0 to Ptn+, was converted to the active surface area of Pt. Pt valence on the surface fluctuates by oxygen molecule adsorption, reaction progression of ORR, and the detachment of generation water molecules. Below 1.0 V, this variation of Pt valence mainly arises on Pt atoms at the topmost surface. If the conversion value between the Pt valence variation and ECSA is determined, the real active area of the Pt catalyst under OCV can be estimated. The aim of this study was to determine the conversion value between the Pt valence variation and ECSA, and its value was verified using single-cell measurements.TEC10E50E (Tanaka Kikinzoku Kogyo K.K., Japan) was used as an electrocatalyst. A half-cell was composed of a carbon counter electrode, a reversible hydrogen electrode (RHE) as a reference electrode, and a 0.1 M HClO4 electrolyte. To vary the Pt utilization rate, three different Pt loading on a working electrode, 17.3 mg-Pt/cm2 (the standard), 8.65 mg-Pt/cm2 (half of the standard), and 173 mg-Pt/cm2 (10 times the standard), were employed. The Pt utilization rate was calculated by dividing an ECSA obtained from electrochemical measurement by theoretical Pt surface area, which was assumed from the average Pt particle size. Calculated Pt utilization rates were used to determine the conversion value.A sing-cell employed TEC10E50E as the cathode catalyst, Nafion NR212 as a polymer electrolyte membrane, TECPd (ONLY) E50E as the anode catalyst, gas diffusion layer, and carbon-based separator with serpentine channel. The catalyst loading in MEA was 0.5 mg-metal cm-2.In-situ XAFS measurements were conducted at BL5S1 and BL11S2 of the Aichi Synchrotron Radiation Center and BL01B1 of SPring-8 in Japan. In half-cell, in-situ XAFS measurements were conducted in fluorescence mode. On the other hand, single-cell tests were evaluated in transmission mode. The white line area of Pt was calculated by fitting the measured XANES spectra in the range of 11.52 keV to 11.60 keV with the arctangent function and Lorentzian function.From the results of ECSAs, Pt utilization rates, and white line areas indicating the Pt valence, the coefficient “α” was determined at 19.7, which was the conversion value between the Pt valence variation and ECSA. When this coefficient “α” was applied to the XANES spectra of OCV in single-cell tests, the real active surface area reflecting the three-phase interface was estimated, and an obtained value approximately agreed with ECSA in the inert gas flow conditions. Thus, the real active surface area of the Pt catalyst at progressing ORR would be estimated using the coefficient “α” discovering this study and in-situ XAFS measurements.

High-Performance Ammonia QCM Sensor Based on SnO2 Quantum Dots/Ti3C2Tx MXene Composites at Room Temperature.

Ammonia (NH3) gas is prevalent in industrial production as a health hazardous gas. Consequently, it is essential to develop a straightforward, reliable, and stable NH3 sensor capable of operating at room temperature. This paper presents an innovative approach to modifying SnO2 colloidal quantum dots (CQDs) on the surface of Ti3C2Tx MXene to form a heterojunction, which introduces a significant number of adsorption sites and enhances the response of the sensor. Zero-dimensional (0D) SnO2 quantum dots and two-dimensional (2D) Ti3C2Tx MXene were prepared by solvothermal and in situ etching methods, respectively. The impact of the mass ratio between two materials on the performance was assessed. The sensor based on 12 wt% Ti3C2Tx MXene/SnO2 composites demonstrates excellent performance in terms of sensitivity and response/recovery speed. Upon exposure to 50 ppm NH3, the frequency shift in the sensor is -1140 Hz, which is 5.6 times larger than that of pure Ti3C2Tx MXene and 2.8 times higher than that of SnO2 CQDs. The response/recovery time of the sensor for 10 ppm NH3 was 36/54 s, respectively. The sensor exhibited a theoretical detection limit of 73 ppb and good repeatability. Furthermore, a stable sensing performance can be maintained after 30 days. The enhanced sensor performance can be attributed to the abundant active sites provided by the accumulation/depletion layer in the Ti3C2Tx/SnO2 heterojunction, which facilitates the adsorption of oxygen molecules. This work promotes the gas sensing application of MXenes and provides a way to improve gas sensing performance.

Modulating Pore Wall Chemistry Empowers Sonodynamic Activity of Two‐Dimensional Covalent Organic Framework Heterojunctions for Pro‐Oxidative Nanotherapy

AbstractCovalent organic frameworks (COFs) have garnered growing interest in the field of biomedicine; however, their application in sonodynamic therapy remains underexplored due to limited understanding of their intrinsic activity and structure–property relationships. Here, we present a pore wall chemistry modulation strategy for empowering sonodynamic activity to two‐dimensional (2D) COF heterojunctions through in situ growth of COFs on bismuth oxycarbonate nanosheets (B NSs). Compared to the negligible sonodynamic effects observed in the pristine B NSs, the 2D heterojunction with vinyl‐decorated COF pore walls demonstrates a 3.6‐fold enhancement in sonocatalytic singlet oxygen generation. This performance also significantly outperforms that of isoreticular COFs functionalized with methoxy or non‐substituted groups. Mechanistic studies reveal that the vinyl groups in the B@COF (BC) heterojunction facilitate the separation and transfer of charge carriers while also enhancing the adsorption of oxygen molecules. Furthermore, peroxymonosulfate (PMS) loading into the porous COFs boosts the therapeutic efficacy of antitumor nanotherapy via sonocatalytic dual oxidative species generation. These findings underscore the critical role of pore wall chemistry in modulating the sonocatalytic properties of COFs, and advance the development of COF‐based sonosensitizers for pro‐oxidative applications.

Modulating Pore Wall Chemistry Empowers Sonodynamic Activity of Two-Dimensional Covalent Organic Framework Heterojunctions for Pro-Oxidative Nanotherapy.

Covalent organic frameworks (COFs) have garnered growing interest in the field of biomedicine; however, their application in sonodynamic therapy remains underexplored due to limited understanding of their intrinsic activity and structure-property relationships. Here, we present a pore wall chemistry modulation strategy for empowering sonodynamic activity to two-dimensional (2D) COF heterojunctions through in situ growth of COFs on bismuth oxycarbonate nanosheets (B NSs). Compared to the negligible sonodynamic effects observed in the pristine B NSs, the 2D heterojunction with vinyl-decorated COF pore walls demonstrates a 3.6-fold enhancement in sonocatalytic singlet oxygen generation. This performance also significantly outperforms that of isoreticular COFs functionalized with methoxy or non-substituted groups. Mechanistic studies reveal that the vinyl groups in the B@COF (BC) heterojunction facilitate the separation and transfer of charge carriers while also enhancing the adsorption of oxygen molecules. Furthermore, peroxymonosulfate (PMS) loading into the porous COFs boosts the therapeutic efficacy of antitumor nanotherapy via sonocatalytic dual oxidative species generation. These findings underscore the critical role of pore wall chemistry in modulating the sonocatalytic properties of COFs, and advance the development of COF-based sonosensitizers for pro-oxidative applications.

Electrochemical characterization of Bi3Ru3O11 – 40 wt% Bi1.6Er0.4O3 as an EOG electrode material

This paper reports on the study of the electrochemical behavior of porous Bi3Ru3O11 – 40 wt% Bi1.6Er0.4O3 electrodes on a Bi2O3 – 10 wt% Bi24B2O39 electrolyte in a symmetric cell configuration by impedance spectroscopy. The dependence of the area specific resistance (ASR) for electrode polarization on the partial pressure of oxygen replaced from PO2−1/2 to PO2−3/4 with decreasing thickness of the layer, which inhibited wetting. This indicates a change in the rate-limiting oxidation-reduction reactions of oxygen. It is assumed that the dissociation of adsorbed oxygen molecules on the active catalytic centers of the triple phase boundary (TPB) is the limiting stage of a surface oxygen exchange, and with a decrease in the layer thickness, additional difficulty in the transfer of gaseous oxygen molecules from the gas phase to these active catalytic centers is observed.

A Bacterial Capturing, Neural Network-Like Carbon Nanotubes/Prussian Blue/Puerarin Nanocomposite for Microwave Treatment of Staphylococcus Aureus-Infected Osteomyelitis.

Staphylococcus aureus (S. aureus)-infected osteomyelitis is a deep tissue infection that cannot be effectively treated with antibiotics. Microwave (MW) thermal therapy (MTT) and MW dynamic therapy (MDT) based on MW-responsive materials are promising for the therapy of bacteria-infected osteomyelitis occurring in deep tissues that cannot be effectively treated with antibiotics. In this work, the MW-responsive system of carbon nanotubes (CNTs)/Prussian blue (PB)/puerarin (Pue) with stable network-like structures is constructed. The PB is grown in situ on the CNTs, and its introduction not only reduces the aggregation of the network-like structures of the CNTs, but the large specific surface area and mesoporous structure can also provide many active sites for the adsorption of oxygen and polar molecules. Pue is a natural anti-inflammatory material that reduces inflammation at the infection site. The composite of the CNTs and PB avoids the skin effect and thus can improve dielectric and reflection losses. The MW thermal response of CNTs/PB/Pue is mainly due to the occurrence of reflection loss, dielectric loss, multiple reflections and scattering, interface polarization, and dipole polarization. In addition, under MW irradiation, the CNTs/PB/Pue can produce reactive oxygen species (ROS), such as singlet oxygen (1O2), hydroxyl radical (·OH).

Molecular Reconfiguration of Disordered Tellurium Oxide Transistors with Biomimetic Spectral Selectivity.

Reconfigurable devices with field-effect transistor features and neuromorphic behaviors are promising for enhancing data processing capability and reducing power consumption in next-generation semiconductor platforms. However, commonly used 2D materials for reconfigurable devices require additional modulation terminals and suffer from complex and stringent operating rules to obtain specific functionalities. Here, a p-type disordered tellurium oxide is introduced that realizes dual-mode reconfigurability as a logic transistor and a neuromorphic device. Due to the disordered film surface, the enhanced adsorption of oxygen molecules and laser-induced desorption concurrently regulate the carrier concentration in the channel. The device exhibits high-performance p-type characteristics with a field-effect hole mobility of 10.02 cm2 V-1 s-1 and an Ion/Ioff ratio exceeding 106 in the transistor mode. As a neuromorphic device, the vision system exhibits biomimetic bee vision, explicitly responding to the blue-to-ultraviolet light. Finally, in-sensor denoising and invisible image recognition in static and dynamic scenarios are achieved.

Temperature-Dependent Oxidation Behavior of Silicon Carbide Surface: Reactive Molecular Dynamics Simulations.

The high-temperature oxidation mechanism of silicon carbide (SiC) is crucial for designing thermal protection systems in aircraft. This study explored the oxidative chemical reaction processes and mechanism on SiC surface and interfaces within the temperature range of 300-2300 K by using reactive molecular dynamics simulation. The oxygen impact on the silica (SiOx) growth of the SiC surface was analyzed, which shows a progressive increase of silica thickness. The simulation results indicated that the oxidation process of SiC was a typical passive oxidation mechanism. With the environmental temperature rising and oxygen impact, the increase of oxidation thickness on the SiC surface undergoes three oxidizing reaction processes: little chemical adsorption of oxygen molecules on the initial surface, rapid oxidation of silicon and carbon, and dramatic oxidation of the interface between the oxidation layer and SiC. Additionally, this work studied the mechanism of oxidation thickness growth and chemical diffusion of oxygen. The oxidation rate is weakened according to the oxygen atom diffusion barrier effect of silica repulsion. Moreover, the kinetic parameters were statistically calculated by fitting the growth of Si-O bonds and their reaction rate constants. Subsequently, the activation energy and pre-exponential factors were derived by using the Arrhenius equation to model the chemical reaction kinetics of the thermal oxidation process. The chemical reaction behaviors of the two stages could be concluded as follows: (i) in stage I, the initial oxidation is reaction rate limiting; (ii) in stage II, SiC oxidation is limited by both the oxidation reaction rate and the oxygen diffusion coefficient of the oxidation layer. The activation energy of stage II increased compared with stage I due to the oxygen atoms diffusion barrier between the oxidation layers. This study on the oxidation and ablation mechanism of the SiC surface at the atomic scale would provide insight into understanding thermal oxidation behavior and the design of ceramic materials.

Phosphorus heteroatom doped BiOCl as efficient catalyst for photo-piezocatalytic degradation of organic pollutant and unveiling the mechanism: Experiment and DFT calculation

A novel phosphorus heteroatom doped bismuth oxychloride (P-BiOCl) catalyst was synthesized and the photo-piezocatalytic degradation of rhodamine B dye performances were explored under the ultrasound vibration and light illumination. The P-BiOCl exhibited excellent photo-piezocatalytic degradation activity, such as an ultra-high reaction kinetic rate constant of 0.3961 min−1, efficient degradation efficiency (94.7 % within 8 min) and excellent stability compared to solely piezocatalysis and photocatalysis. More impressively, these outstanding performances of P-BiOCl exceeded pure BiOCl and most other catalytic materials systems. The relevant experimental and density functional theory (DFT) calculation results were exhibited to clarify enhanced photo-piezocatalytic mechanism. The introduction of P heteroatom could reduce the bandgap of BiOCl, modulate electronic structure and charge redistribution, provide novel electron channel to promote electron transfer and restrain charge carriers recombination. Additionally, P-doped could also enhance the adsorption of oxygen and water molecules, promote intrinsic catalytic activity, leading to the increased production of active free radicals ·O2– and ·OH, thus significantly boosting the efficiency of organic pollutant degradation. This work provides a comprehensive understanding of heteroatom doping enhancing photo-piezocatalytic activity and presents a potential new strategy for designing highly efficient catalysts for wastewater treatment.

Superhydrophilic Surface Creation and Its Temporal Transition to Hydrophobicity on Copper via Femtosecond Laser Texturing

We analyzed a process to fabricate a superhydrophilic surface on copper by forming various laser-induced periodic surface structures (LIPSS) using a Ti/sapphire femtosecond laser. For these structured surfaces, the correlation between the surface structure and the wetting characteristics was analyzed by scanning electron microscopy, atomic force microscopy, and contact angle (CA) measurement. X-ray photoelectron spectroscopy (XPS) was also employed to analyze variation of the elemental composition of the surfaces. The laser treatment produced micro/nanostructures composed of ripples whose length and width are in microscale and nanoscale, respectively. At specific conditions, the CA of a water droplet was reduced to less than 1°. The superhydrophilcity is attributed to the effect of nanoholes and nanoclusters, which consist of copper (II) oxide and copper hydroxide, having a hydrophilic effect on LIPSS. However, the pristine superhydrophilic surface spontaneously became hydrophobic after being exposed to air at room temperature for about 10 days. According to XPS analysis, the surface’s transition to hydrophobic is attributed not only to the decomposition of Cu(OH)2 but also to the adsorption of oxygen molecules and/or airborne organic molecules containing carbon, which further influences the wettability.

Spatial Identification of Mott-Schottky Effect at Electrocatalytic Pd/Metal Oxide Interfaces for the Oxygen Reduction Reaction.

To elucidate the microstructure and charge transfer behavior at the interface of Pd/metal oxide semiconductor (MOS) catalysts and systematically explore the crucial role of the Mott-Schottky effect in the oxygen reduction reaction (ORR) electrocatalysis process, this study established a testing system for spatially identifying Mott-Schottky effects and electronic properties at Pd/MOS interfaces, leveraging highly sensitive Kelvin probe force microscopy (KPFM). This system enabled visualization and quantification of the surface potential difference and Mott-Schottky barrier height (ΦSBH) at the Pd/MOS heterojunction interfaces. Furthermore, a series of Pd/MOS Mott-Schottky catalysts were constructed based on differences in work functions between Pd and n-type MOS. The abundant oxygen vacancies in these catalysts facilitated the adsorption and activation of oxygen molecules. Notably, the intensity of the built-in electric field in the Pd/MOS Mott-Schottky catalysts was calculated through surface potential and zeta potential analysis, systematically correlating the Mott-Schottky effect at the heterojunction interface of Pd/MOS with ORR activity and kinetics. By comprehensively exploring the correlation between the Mott-Schottky effect and ORR performance in Pd/MOS catalysts using the KPFM testing system, this study provides necessary tools and approaches for a deep understanding of heterogeneous interface charge transfer mechanisms, as well as for optimizing catalyst design and enhancing ORR performance.

Regulation of surface oxygen (OV, OC) and enhancement of triethylamine sensing performance of MOF-derived Co3O4 hollow nanocubes by g-C3N4 coupling

The regulation of oxygen defects and chemisorbed oxygen plays an essential role in the sensing behavior of oxide semiconductor sensors. MOF derivatization and the construction of heterojunction are potential approaches to obtain high-performance sensors. Here, MOF-derived Co3O4 hollow nanocubes coupled with 2-dimensional g-C3N4 were prepared and further applied to triethylamine sensing. XPS results reveal the significant increase of oxygen defects and chemisorbed oxygen in the composite. Calculations of oxygen escape energy show that the construction of oxygen defects mainly originates from the anoxic environment caused by g-C3N4 coating. And calculation of surface models indicates that oxygen vacancies could enhance the interaction and charge transport at the heterointerface, and simultaneously serves as an adsorption site to improve the adsorption and activity of oxygen molecule. Combined with the energy band adjustment, Co d‐band center regulation and diffusion channel resulted from g-C3N4 coupling, the sensor based on the composite shows higher response, faster response speed and better selectivity to triethylamine. This study could provide a reference for the regulation of oxygen defects, chemisorbed oxygen, and the preparation of high-performance sensors.

Enhanced catalytic activity of novel sea urchin-like spinel for advanced electrochemical energy conversion

Through precise morphological engineering, novel sea urchin-like spinel NiCo2O4 (NCO) was successfully synthesized and thoroughly investigated as a bifunctional electrode for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In contrast to traditional NCO, the distinctive scattered nanofiber microstructure of NCO prepared via hydrothermal at 100 ℃ (HT100) increases the specific surface area, introduces more oxygen vacancies, reduces the bandgap, enhances the diffusion, adsorption, and dissociation processes of oxygen molecules, thereby promoting rapid electron transfer and augmenting the number of active sites for both ORR and OER. At 800 °C, under the ORR model, NCO-HT100 exhibits an impressive output performance of 920 mW cm−2, surpassing traditional NCO by 47.8 %. Simultaneously, under the OER model, NCO-HT100 achieves a current density of 134.29 mA cm−2. Compared with conventional NCO, sea urchin-like NCO-HT100 displays lower Tafel slopes and overpotentials in alkaline solution at room temperature, indicating superior OER performance. These findings highlight that the sea urchin-like NCO-HT100 stands out as an advanced bifunctional electrode material for both ORR and OER. The insights gained from this research provide pivotal guidance for the future development of multifunctional electrode materials in energy conversion device applications.

Oxygen-defect rich SnO2-based homogenous composites for fast response and recovery hydrogen sensor

As a kind of green energy, hydrogen (H2) has been widely concerned and applied by people. One of the biggest challenges for sensing applications is the quick detection of hydrogen leaks or their release in various conditions, particularly in large electric vehicle batteries. This study successfully constructed a quick response and recovery hydrogen sensor based on the In2O3-SnO2 heterojunction. The response and recovery time of the In2O3-SnO2 hydrogen sensor is 1.1/1.9 s to 50 ppm H2. This is reduced to 11.0 %/9.5 % compared to the SnO2 hydrogen sensor. This sensor's remarkable gas detecting properties are mainly attributed to the In2O3-SnO2 heterojunction creation, crystal structure modification, and increased specific surface area (92.9 m2/g). Homogenous In2O3-SnO2 nanocomposites contain more oxygen defects, which is the primary factor enhancing the sensor's ability to detect gases. Firstly, indium ions are incorporated in the lattice of SnO2 results in lattice distortion and enhances the presence of oxygen deficiency in the composites, which plays a pivotal role in achieving rapid response and recovery of the sensor. Secondly, In2O3-SnO2 heterostructures promote rapid adsorption of oxygen molecules and target gases by facilitating effective electron mobility on their surface. The quicker response and recovery times of hydrogen sensors based on In2O3-SnO2 heterojunctions are observed. This innovative approach to creating fast-responding gas sensors highlights the promise of heterojunction-based hydrogen sensors for real-time H2 monitoring and opens up new research directions.

Determining the influence of relative humidity on the working parameters of a gas sensor based on zinc oxide

This paper investigates the dependence of operating parameters of a gas sensor based on zinc oxide obtained by the method of direct current magnetron sputtering. The production of gas sensor films was carried out using a VUP-5M vacuum unit with an original material-saving magnetron. The study of the dependence of the working parameters of the gas sensor was carried out under standard conditions. It was found that with increasing humidity, the electrical resistance of the gas sensor decreases and, accordingly, the sensitivity to the target gas decreases. A significant reaction of the gas sensor to an increase in humidity was observed in the range of 65–80 % relative humidity. The mechanism of influence of relative humidity on the sensitivity of a gas sensor based on ZnO was investigated. The change in resistance of the gas sensor is caused by trapped electrons on adsorbed oxygen molecules on the surface of the sensitive layer. The capture of electrons from the conduction zone leads to bending of the conduction zone and an increase in the space charge zone, respectively, to a change in the resistance of the sensitive layer of the gas sensor. In the atmosphere, when O2 molecules are adsorbed on the ZnO surface, they remove an electron from the conduction band. The reaction of oxygen adsorbed on the ZnO surface with reducing gases and the replacement of adsorbed oxygen with other molecules changes the bending of the conduction band and reduces the area of space charge. Adsorption of water on the surface of zinc oxide occurs according to the dissociation mechanism, which consists in the adsorption of steam molecules or hydroxyl groups with the subsequent displacement of previously adsorbed oxygen and free electrons and, accordingly, leads to a decrease in the sensitivity of the gas sensor. In addition, the adsorption of water vapor (H2O) molecules leads to less chemisorption of oxygen species on the ZnO surface due to the reduction of the surface area, which is responsible for the sensor response. Approaches to reduce the influence of relative humidity on the sensitivity of a gas sensor based on zinc oxide have been proposed

Ultrasensitive detection and sensitivity mechanism of SO2F2 in SF6 decomposition product based on TiO2-NiS heterojunction

SO2F2 is a typical fault product of SF6 electrical insulation equipment. Detecting SO2F2 can indicate whether the equipment is faulty. SO2F2 is a hazardous gas that can cause harm to the human body. This study reports on the development of the SO2F2 sensor using TiO2-NiS for the first time, and the investigation of its gas sensitivity to SO2F2 in SF6 background and air. The effective construction of the TiO2-NiS heterojunction was characterized via the XRD, SEM, and TEM. The TiO2-NiS heterojunction sensor for SO2F2 has a working temperature of 150°C in both SF6 and air environments with the response and recovery time of 6 s/2 s to 5 ppm SO2F2 in the air and 5 s/6 s in the SF6 environments, respectively. The sensor has a strong linear fit and a detection limit of 100 ppb. The long-term stability, selectivity, resistance to moisture, and responsiveness/recovery are features of this sensor. Furthermore, it was demonstrated that SO2F2 adsorption performance on the TiO2-NiS heterojunction outperformed that of TiO2 and NiS based on first principles, and density of states and differential charge density provided a more detailed description of the interaction between SO2F2 gas and the TiO2-NiS heterojunction. The oxygen competitive adsorption of SO2F2 and lattice oxygen molecules on the surface of TiO2-NiS heterojunction, as well as the interaction between adsorbed F2− on the TiO2-NiS heterojunction surface and SO2F2, may be used to characterise the sensing mechanism in the SF6. At the same time, the prepared SO2F2 sensor can effectively measure the concentration of SO2F2 through hardware, and give early warning when the concentration exceeds the safe value.

Oxygen reduction reaction activity of Co3O4-modified Pt-graphene electrocatalysts

Abstract In this paper, the ORR activity of Pt/Co3O4-modified N-doped graphene electrocatalysts was investigated based on DFT theory. The Dmol3 module in Materials Studio software was used to optimize the construction of NG models under different doping conditions and to calculate the adsorption and desorption properties of oxygen molecules by optimizing the conformation of Pt13 clusters and substrates. A comparative analysis revealed that the Co3O4 modification reduced the oxygen adsorption energy of the Pt/G catalyst. However, after N doping, the oxygen adsorption energy of Pt/Co3O4/NG was superior to that of Pt/NG. After theoretical analysis, it was determined that it was because the doping of N atoms in graphene could promote the release of oxygen vacancies in Co3O4 and strengthen the adsorption interaction between Pt and graphene carriers to improve the oxygen adsorption energy.

Efficient photocatalytic molecular oxygen activation by TTF-based heterojunction for water purification

Tetrathiafulvalene (TTF), one of the well-known organic photoelectric materials, was served as active sites to accelerate the activation of molecular oxygen to degrade organic pollutants. Herein, a kind of Z-scheme heterojunction photocatalysis was constructed based on g-C3N4 and TTF. According to the experimental results, the mechanism of Z-scheme heterojunction was supported, in which photogenerated electrons transferred from g-C3N4 to TTF. More importantly, TTF on the catalyst surface could serve not only as electron donor, but also as the terminal active site to transfer photoexcited electrons to adsorbed oxygen molecules, producing mass of ⋅O2–. Meanwhile, the activation rate constant of TCN-5 for RhB was 0.0624 min−1, which was 10 and 5 times of g-C3N4 and TTF, respectively. In addition, the results of EPR spectra, rotating disk electrode measurement and molecular oxygen activation measurement also demonstrated that this catalyst was energetically favorable to generate ⋅O2– through the single-electron reduction pathway of molecular oxygen. Finally, four possible photodegradation routes for RhB were proposed based on the results of HPLC-MS. This work provides a new insight on the application of organic photoelectric materials in the purification of wastewater by the molecular oxygen activation.