Chemical Vapor Deposition Technique Research Articles

Temperature-dependent epitaxial evolution of carbon-free corundum α-Ga2O3 on sapphire

Unintentionally doped carbon impurities from organometallic precursors are primary sources of carrier compensation and mobility degradation in wide bandgap semiconductors, leading to lowered performance of power electronic devices. To address this challenge, carbon-free α-Ga2O3 single-crystalline thin films were heteroepitaxially grown on sapphire substrates by using gallium inorganic precursors through a mist chemical vapor deposition technique. Determined through a temperature dependence of growth rates, three distinct growth regimes are identified: the surface reaction limited regime below 480 °C, the mid-temperature mass-transport limited regime (480 °C–530 °C) and the high temperature limited regime related to desorption or phase transition. With an optimized around 530 °C, the densities of screw and edge dislocations are reduced to 7.17 × 106 and 7.60 × 109 cm−2, respectively. Notably, carbon incorporation was eliminated in the α-Ga2O3 grown by inorganic GaCl3, as evidenced by the absence of carbon-related vibrational bands in Raman scattering analysis, while crystalline quality was comparable to that grown with organometallic precursors. The high solubility of GaCl3 in water is expected to enable the rapid growth of high purity α-Ga2O3 with improved electronic transport performances.

Single‐Step Chemical Vapor Deposition of Methyl Ammonium Lead Halide Perovskite for p–i‐n Solar Cells

AbstractMetal halide perovskite solar cells being one of the fastest emerging technologies for renewable energy still has to become more industry friendly in a way that will allow using it for thin film modules or tandems with conventional silicon devices. The simplest way to achieve this is to use chemical vapor deposition (CVD) technique for tandem production. In this work, we show a method for a single step production of MAPbI3 films in a simple two‐zone CVD reactor from lead diacetate and methyl‐ammonium iodide powders. Obtained films show highly ordered cubic MAPbI3 phase with a thickness of 400–500 nm, good photoluminescence response and absorption band edge similar to spin‐coated film. We used those films to produce p‐i‐n solar cells with ITO/NiO/MAPbI3/C60/Cu structure. The best cell showed negligible 0.23 % PCE right after the manufacturing but significantly improved to 5.5 % PCE after 8 hours of storage in the dark. The main limiting factor affecting the efficiency is low current density, which we attribute to non‐optimized growth conditions; however, our approach is a first step to a single step CVD deposition of MAPbI3 on any type of substrates including texturized silicon subcells for better overall efficiency

Defect Analysis in a Long-Wave Infrared HgCdTe Auger-Suppressed Photodiode.

Deep defects in the long-wave infrared (LWIR) HgCdTe heterostructure photodiode were measured via deep-level transient spectroscopy (DLTS) and photoluminescence (PL). The n+-P+-π-N+ photodiode structure was grown by following the metal-organic chemical vapor deposition (MOCVD) technique on a GaAs substrate. DLTS has revealed two defects: one electron trap with an activation energy value of 252 meV below the conduction band edge, located in the low n-type-doped transient layer at the π-N+ interface, and a second hole trap with an activation energy value of 89 meV above the valence band edge, located in the π absorber. The latter was interpreted as an isolated point defect, most probably associated with mercury vacancies (VHg). Numerical calculations applied to the experimental data showed that this VHg hole trap is the main cause of increased dark currents in the LWIR photodiode. The determined specific parameters of this trap were the capture cross-section for the holes of σp = 10-16-4 × 10-15 cm2 and the trap concentration of NT = 3-4 × 1014 cm-3. PL measurements confirmed that the trap lies approximately 83-89 meV above the valence band edge and its location.

In-situ growth of vertically stacked 2D SnS2/SnS heterostructure for highly sensitive and rapid room temperature NO2 gas sensor

Construction of 2D heterostructure is a potential strategy to improve the sensing performance of 2D layered materials owing to the high-quality of heterointerfaces. This attributed to the remarkable electronic band alignment between the constituent materials and their distinctive characteristics. Woefully, very limited attempts have been taken to investigate the effect of 2D heterointerface for gas sensing applications. Here, the SnS2/SnS heterostructure is fabricated on a SiO2/Si substrate using a single-step atmospheric chemical vapor deposition technique for room temperature NO2 sensing. The heterostructure has imparted a 1.3 times enhancement in response (S(%)), with ultra-fast response (τres) and recovery time (τrec) of 32 s and 382 s, towards 40 ppm of NO2 at 30 °C. Moreover, the impact of humidity on the sensing performance of SnS2/SnS has also been studied, confirming its negligible effect on relative humidity. Additionally, it also demonstrates a remarkable stability of 93% over a period of 40 days. Besides, due to strong adsorption energy of SnS2 (1914 meV) and SnS (600 meV) towards NO2 endorses the reaction kinetic parameters validated by the gas adsorption/desorption isotherm analysis of heterostructure. The substantial interface contacts between the SnS2/SnS heterostructure facilities the fermi-level mediated charge transfer, contributing significantly towards the improvement in sensing performance. Therefore, the formation of hierarchical 2D heterostructure with electron depletion layer can be considered as a conducive way for the future development low-powered gas sensor.

Comparison of SiNx Dielectric Layer Grown by Plasma‐Enhanced Chemical Vapor Deposition, Low‐Pressure Chemical Vapor Deposition, and Metal‐Organic Chemical Vapor Deposition in Diamond‐ and GaN‐Based Integrated Devices

To address the issue of heat dissipation caused by the high output power density of gallium nitride (GaN) devices, using diamond‐integrated devices is an effective solution. Recent studies have suggested that incorporating a dielectric layer, such as silicon nitride (SiNx), between diamond and GaN can improve adhesion while also reducing thermal boundary resistance (TBR). In this study, plasma‐enhanced chemical vapor deposition (CVD), low‐pressure CVD, and metal‐organic CVD (MOCVD) techniques are utilized to grow the SiNx layer. The interface behavior of diamond/SiNx/GaN is analyzed through scanning electron microscopy, transmission electron microscopy (TEM), scanning TEM, and energy‐dispersive X‐ray spectroscopy, while time‐domain thermoreflectance measurement is used to characterize thermal properties. After analyzing the impact of the growth dielectric layer on the interface thermal resistance of the three growth modes, it is concluded that the dielectric layer produced by the MOCVD technique exhibits a smoother surface and lower TBR compared to the other two methods. Therefore, the use of the MOCVD technique is recommended to achieve optimal thermal performance in diamond/SiNx/GaN systems.

Influence of the Incorporation of Nd in ZnO Films Grown by the HFCVD Technique to Enhance Photoluminiscence Due to Defects

In this work, optical–structural and morphological behavior when Nd is incorporated into ZnO is studied. ZnO and Nd-doped ZnO (ZnO-Nd) films were deposited at 900 °C on Silicon n-type substrates (100) by using the Hot Filament Chemical Vapor Deposition (HFCVD) technique. For this, pellets were made by from powders of ZnO(s) and a mixture of ZnO(s):Nd(OH)3(s). The weight percent of the mixture ZnO:Nd(OH)3 in the pellet is 1:3. The gaseous precursor generation was carried out by chemical decomposition of the pellets using atomic hydrogen which was produced by a tungsten filament at 2000 °C. For the ZnO film, diffraction planes (100), (002), (101), (102), (110), and (103) were found by XRD. For the ZnO-Nd film, its planes are displaced, indicating the incorporation of Nd into the ZnO. EDS was used to confirm the Nd in the ZnO-Nd film with an atomic concentration (at%) of Nd = 10.79. An improvement in photoluminescence is observed for the ZnO-Nd film; this improvement is attributed to an increase in oxygen vacancies due to the presence of Nd. The important thing about this study is that by the HFCVD method, ZnO-Nd films can be obtained easily and with very short times; in addition, some oxide compounds can be obtained individually as initial precursors, which reduces the cost compared to other techniques. Something interesting is that the incorporation of Nd into ZnO by this method has not yet been studied, and depending on the method used, the PL of ZnO with Nd can increase or decrease, and by the HFCVD method the PL of the ZnO film, when Nd is incorporated, increases more than 15 times compared to the ZnO film.

Chemiresistors Based on Hybrid Nanostructures Obtained from Graphene and Conducting Polymers with Potential Use in Breath Methane Detection Associated with Irritable Bowel Syndrome.

This paper describes the process of producing chemiresistors based on hybrid nanostructures obtained from graphene and conducting polymers. The technology of graphene presumed the following: dispersion and support stabilization based on the chemical vapor deposition technique; transfer of the graphene to the substrate by spin-coating of polymethyl methacrylate; and thermal treatment and electrochemical delamination. For the process at T = 950 °C, a better settlement of the grains was noticed, with the formation of layers predominantly characterized by peaks and not by depressions. The technology for obtaining hybrid nanostructures from graphene and conducting polymers was drop-casting, with solutions of Poly(3-hexylthiophene (P3HT) and Poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-bithiophene] (F8T2). In the case of F8T2, compared to P3HT, a 10 times larger dimension of grain size and about 7 times larger distances between the peak clusters were noticed. To generate chemiresistors from graphene-polymer structures, an ink-jet printer was used, and the metallization was made with commercial copper ink for printed electronics, leading to a structure of a resistor with an active surface of about 1 cm2. Experimental calibration curves were plotted for both sensing structures, for a domain of CH4 of up to 1000 ppm concentration in air. A linearity of the curve for the low concentration of CH4 was noticed for the graphene structure with F8T2, presenting a sensitivity of about 6 times higher compared with the graphene structure with P3HT, which makes the sensing structure of graphene with F8T2 more feasible and reliable for the medical application of irritable bowel syndrome evaluation.

Synergistic engineering of palladium-cobalt nanoalloys on graphite sheet for efficient and sustainable hydrogen evolution reaction

The electrochemical hydrogen evolution reaction (HER)—a carbon-free route for hydrogen (H2) production—is of the utmost importance for H2-economy. Currently, HER performance is mainly restricted by the lack of promising alternatives to Pt-based electrocatalysts. In this study, we developed bimetallic PdCo alloy thin films with outstanding catalytic properties for the HER under acidic conditions. A simple aerosol-assisted chemical vapor deposition technique designed in-house was used to produce bimetallic alloy thin films on graphite sheets. The thin-film morphological patterns were significantly changed by varying the deposition time from 30 to 90 min. The optimized PdCo catalyst deposited for 30 min had a unique nanostructure with numerous active sites and exhibited faster HER kinetics than its analogs and pure Pd. As-prepared PdCo-30 electrode produced current densities of 10 and 1000 mA cm−2 at overpotentials of 41 and 161 mV, respectively, along with a Tafel slope of 42 mV/dec, high conductivity (0.28 Ω), and catalytic stability of ∼24 h in 0.5 M H2SO4. The excellent HER activity of the PdCo alloy was attributed to the synergy between the noble transition metal and the thin nanostructured layer of the bimetallic catalyst, which promoted formation of extensive electroactive sites on the conductive graphite surface. Density functional theory calculations confirmed the experimental findings. The Gibbs free energy (ΔGH*) of the PdCo alloy (−0.43 eV) was significantly lower than that of pure Pd (−0.57 eV), confirming the enhancement in HER activity due to the introduction of Co into the Pd lattice.

Pulsed Electro Decoration of Carbon Nanotubes with FexZn1−xS

Pulsed Electro Decoration of Carbon Nanotubes with FexZn1−xS

Epitaxial growth of high-quality GaN with a high growth rate at low temperatures by radical-enhanced metalorganic chemical vapor deposition

Using our recently developed radical-enhanced metalorganic chemical vapor deposition (REMOCVD) technique, we have grown gallium nitride (GaN) on bulk GaN and GaN on Si templates. Three features make up this system: (1) applying very high-frequency power (60 MHz) to increase the plasma density; (2) introducing H2 and N2 gas in the plasma discharge region to produce active NHx radical species in addition to nitrogen radicals; and (3) supplying radicals under remote plasma arrangement with a Faraday cage to suppress charged ions and photons. Using this new REMOCVD system, it was found that high-quality crystals can be grown at lower temperatures than that of MOCVD but the disadvantage was that the growth rate was smaller as 0.2–0.8 μm/h than that by MOCVD. In the present work, we have used a pBN inner shield to prevent the deactivation of radicals to increase the growth rate. The growth conditions such as the plasma power, trimethylgallium (TMG) source flow rate, N2 + H2 gas mixture flow rate, and the ratio of N2/H2 were optimized and it was found that the growth rate could be increased up to 3.4 μm/h with remarkably high crystalline quality comparable to that of MOCVD. The XRD-FWHM of GaN grown on the GaN/Si template and the bulk GaN substrate were 977 arcsec and 72 arcsec respectively. This work may be very promising to achieve high-power GaN/GaN devices.

High-performance GeSi/Ge multi-quantum well photodetector on a Ge-buffered Si substrate.

This work demonstrates a high-performance photodetector with a 4-cycle Ge0.86Si0.14/Ge multi-quantum well (MQW) structure grown by reduced pressure chemical vapor deposition techniques on a Ge-buffered Si (100) substrate. At -1 V bias, the dark current density of the fabricated PIN mesa devices is as low as 3 mA/cm2, and the optical responsivities are 0.51 and 0.17 A/W at 1310 and 1550 nm, respectively, corresponding to the cutoff wavelength of 1620 nm. At the same time, the device has good high-power performance and continuous repeatable light response. On the other hand, the temperature coefficient of resistance (TCR) of the device is as high as -5.18%/K, surpassing all commercial thermal detectors. These results indicate that the CMOS-compatible and low-cost Ge0.86Si0.14/Ge multilayer structure is promising for short-wave infrared and uncooled infrared imaging.

Home-made chemical vapor deposition-based synthesis of binder-free nanostructured magnesium-molybdenum-sulfide electrode materials for supercapacitor application

Molybdenum disulfides (MoS2) is considered as promising electrode materials (E-M) for high electrochemical performance (ECP) of lithium-ion batteries and supercapacitors due to their layered nanostructures. Herein, MoS2, MgS and hetrostructure MgS/MoS2 E-Ms comprising of nano-particles/sheets/needles like structures are synthesized on Nickel foam (Ni–F) by a simple home-made chemical vapor deposition (CVD) technique. The XRD analysis confirmed the formation of MoS2, MgS and MgS/MoS2 polycrystalline E-Ms growing along different directions. The FESEM analysis is confirmed that the addition of MgS layer over the surface of MoS2 change the surafce morphology from nano-particles to nano-needles. The change in structural and microstructural features is indicated the appearance of defects, micro-strain and dislocations density which are fruitful for excellent ECP. The cyclic voltammetry analysis is indicated the pseudocapacitive nature of the synthesized E-Ms. The maximum specific capacitance values for MoS2/Ni–F, MgS/Ni–F and MgS/MoS2/Ni–F E-Ms are 1273, 1688 and 3934 F/g at 1 A/g respectively. Moreover, the addition of MgS layer over MoS2/Ni–F is revealed the excellent cyclic stability of 98.76 % at current density of 10 A/g after 4000 cycles, energy density values are ranged from 79 to 136 W h/kg with homologous power density of 250–2500 W/kg and very small charge transfer resistance. The simulations of Power's Law and Dunn's model is confirmed that the excellent ECP is due to both capacitive and diffusive controlled contributions of heterostructured MgS/MoS2/Ni–F E-Ms. Additionally, MgS/MoS2/Ni–F E-Ms have both battery and pseudocapacitive nature due to unique nano-needles like morphology. The excellent electrochemical properties of MgS/MoS2/Ni–F E-Ms substantiate their potential applications in portable energy storage devices.

Lasing from a Large-Area 2D Material Enabled by a Dual-Resonance Metasurface.

Semiconducting transition metal dichalcogenides (TMDs) have gained significant attention as a gain medium for nanolasers, owing to their unique ability to be easily placed and stacked on virtually any substrate. However, the atomically thin nature of the active material in existing TMD lasers and the limited size due to mechanical exfoliation presents a challenge, as their limited output power makes it difficult to distinguish between true laser operation and other "laser-like" phenomena. Here, we present room temperature lasing from a large-area tungsten disulfide (WS2) monolayer, grown by a wafer-scale chemical vapor deposition (CVD) technique. The monolayer is placed on a dual-resonance dielectric metasurface with a rectangular lattice designed to enhance both absorption and emission, resulting in an ultralow threshold operation (threshold well below 1 W/cm2). We provide a thorough study of the laser performance, paying special attention to directionality, output power, and spatial coherence. Notably, our lasers demonstrated a coherence length of over 30 μm, which is several times greater than what has been reported for 2D material lasers so far. Our realization of a single-mode laser from a CVD-grown monolayer presents exciting opportunities for integration and the development of real-world applications.

Design, preparation and diffusion research of the W coating used in W-based cermet for nuclear thermal propulsion

The fissile fuel agglomeration and loss in the tungsten (W) based ceramic-metallic (cermet) fuel element are the major challenges for application in nuclear thermal propulsion (NTP). The previous research indicated that a W coating deposited on the surface of uranium dioxide (UO2) by the fluidized bed chemical vapor deposition (CVD) technique is an efficient way to achieve the uniform distribution of fuel particles and reduce fuel loss simultaneously. However, the W layers' resulting thicknesses differ, which is not conducive to achieving high fuel loading. Therefore, in this study, the appropriate thickness of the W coating is first investigated by COMSOL Multiphysics modeling. Through contrastive analyses, the W layer with a thickness of about 5–10 μm is considered to be the optimal choice, where the maximum loading capacity of the fissile fuel can be achieved with a volume fraction of about 60%. Based on the above calculations, the CVD technique is employed to produce the optimized thickness of the W layer by precisely adjusting the deposition time at 900 °C. This approach is taken after determining the critical influencing factor that governs the performance of the W layer. Experimental results show that the highly dense W layer presents a uniform thickness and fine-grained size. As the only structural and protective layer, the application of this W coating provides a barrier for blocking the inward diffusion of hydrogen (H2) to stop the detrimental chemical reactions between UO2 and H2, thus lowering fuel loss. The spark plasma sintering (SPS) demonstrates that zirconium dioxide (ZrO2) particles as the surrogate for UO2 exhibit a homogeneous distribution without any direct contact in the W matrix because of the presence of the W coating. Despite the fact that the interface between the W coating and the W matrix exhibits remarkable bonding, making it difficult to clearly discern the boundaries due to surface diffusion and atomic binding, the existence and integrity of the W coating after high-temperature sintering is unequivocally confirmed through interface TEM observations and the uniform dispersion of coated particles within the W-Y2O3 matrix. Furthermore, the fine-grained W coating has been demonstrated to effectively hinder the diffusion of H2 isotopes through permeation and diffusion tests. This comprehensive study not only aids in establishing the optimal geometrical thickness for the W coating but also underscores its pivotal role in W-based cermet fuels for NTP system.

Chemical Vapor Deposition of Two-Dimensional Magnetite Nanosheets and Raman Study of Heat-Induced Oxidation Reaction

Two-dimensional magnetic materials exhibiting antiferromagnetic properties at room temperature offer significant potential for developing next generation spintronic nanodevices. This work presents controlled synthesis of two-dimensional magnetite (Fe3O4) nanosheets utilizing lost cost and convenient chemical vapor deposition (CVD) technique, Raman spectroscopy study of laser-heating and annealing induced oxidation reaction. X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy, and Raman spectroscopy characterizations demonstrated that Fe3O4 nanosheets down to about 10 nm with good crystalline quality, surface uniformity, and minimal defects can be obtained by optimizing the growth parameters in our CVD synthesis. Both laser-heating and annealing studies of Fe3O4 nanosheets indicated that ferrimagnetic Fe3O4 nanosheets gradually change to antiferromagnetic α-Fe2O3 nanosheets at about 400 °C. Our study showed that Raman spectroscopy provides a convenient and powerful method for estimating heat-induced temperature and investigating oxidation reaction.

Electrochemical characteristics of nano-structure TiCN coatings on the tool steel deposited by PACVD in various solutions

This study investigates The electrochemical behavior of various nano-structure TiCN coatings prepared using a plasma-assisted chemical vapor deposition technique in acidic and alkaline solutions. The N2/Ar ratio was varied to explore its effect on the microstructure and electrochemical properties of coatings on the steel cold-work tool. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PP) measurements were carried out in various corrosive solutions. Field emission scanning electron microscopy and X-ray diffraction were also utilized to evaluate the microstructure and phase detection. The EIS results showed that the resistance of TiCN coatings increased by about 94.3 % based on the equiaxed structure and small size of the coating cluster in 3.5 % wt NaCl solution after 24 h. The lowest corrosion rate with a value of 5.9 µA cm−2 in Ringer's solution at 37 °C after 24 h was attributed to the TiCN coating with the N2/Ar ratio of 0.4 according to exhibiting the highest Ti content and changes in present phases. The N2/Ar ratio of 0.7 effectively increased the impedance resistance to 97.5 % based on PP test results in 3 M H2SO4 solution. This behavior was related to the lowest value of the C/N ratio and the highest coating thickness.

First-principles investigations and MOCVD growth of Si-doped β-Ga2O3 thin films on sapphire substrates for enhancing Schottky barrier diode characteristics

In the realm of high-power electronics, the potential of gallium oxide (β-Ga2O3) as a front-runner material has garnered significant attention due to its wide bandgap and the capacity to withstand high critical electric fields. To push the boundaries of performance for β-Ga2O3 devices, a meticulous exploration into the effects of silicon (Si) doping on β-Ga2O3 films was carried out using the metalorganic chemical vapor deposition (MOCVD) technique with various tetraethoxysilane (TEOS) flow rates (0–30 sccm). The Si-doped β-Ga2O3 films were systematically studied and characterized using XRD, SEM, and XPS techniques. XRD patterns demonstrated the preservation of the β-Ga2O3 monoclinic structure in the Si-doped β-Ga2O3 films, without any evidence of secondary phases. In addition to this, first-principles calculations were performed to explore the incorporation of Si atoms in Ga2O3 supercells, which revealed the preference of Si atoms to occupy substitutional Ga tetrahedral sites within the Ga2O3 lattice. Through the utilization of Si-doped β-Ga2O3 films, a unique design of donut-shaped Schottky barrier diode (SBD) was successfully engineered. Remarkably, the Si-doped β-Ga2O3 SBD (employed with 20 sccm TEOS flow rate) exhibited the breakdown voltage (Vbr) of 497 V and Baliga's Figure of Merit (BFOM) value of 1.16 kW/cm2, which is five-order higher BFOM compared to undoped β-Ga2O3 SBD. This substantial improvement in BFOM underscores the significant potential of Si-doped β-Ga2O3 films for high-power electronics, opening avenues for enhanced device efficiency and capabilities.

Growth of boron-doped diamond-like carbon films from a low-pressure high-density plasma in inductively coupled chemical vapour deposition

The main objective of this work was the preparation and optimization of boron-doped diamond-like carbon (DLC) films having a good crystalline structure, and electronic and optical properties, at an extremely low deposition pressure and relatively low growth temperature, by varying the flow rates of precursor gases (CH4, B2H6, and Ar) in the plasma controlled at 800 W of RF power. Planar inductively coupled plasma-enhanced chemical vapour deposition technique was used to enable deposition at ∼5.33 Pa and 450 °C, at a constant negative substrate bias of -40 V. The flow rate of the dopant gas (B2H6) was changed to obtain a set of samples, while the precursor gas (CH4) flow rate was kept fixed. The doped sample, prepared with B2H6/CH4 ratio (r) = 1 %, was found to possess a maximum ID/IG (intensity ratio of the D peak with the G peak) of ∼0.819 and a minimum IDia/IG ratio (relative intensity of the Diamond peak to the G peak) of ∼1.149. A high sp3 content of ∼50 % was revealed from the X-ray photoelectron spectroscopy analysis and the transmission electron microscopy images also indicated the presence of prominent 〈111〉, 〈220〉, and 〈311〉 crystallographic planes. The B-doped DLC film possessed enhanced electrical conductivity (σRT) of ∼3.02 ×10−5 S cm−1 relative to the intrinsic DLC films, a corresponding minimum of activation energy (ΔEH) (as calculated in the above room-temperature regime) of ∼170 meV, an optical band gap (Eg) of ∼3.35 eV, and the root mean square roughness of ∼48.12 nm.

Nanostructured boron-doped diamond electrodes for two-electron water oxidation to produce hydrogen peroxide

Boron-doped diamond (BDD) electrodes have been widely used in water treatment, e.g., degradation of antibiotics and pigments for water purification. Hydrogen peroxide production by two-electron electrochemical oxidation of water is a green and attractive method that has the potential to replace the conventional anthraquinone autoxidation (AO) process. In this study, BDD films were prepared on single-crystal silicon wafers by using hot-filament chemical vapor deposition (HFCVD) technique. Then, dense tubular nanostructure (nanotubes) arrays were prepared on the BDD films employing inductively coupled plasma (ICP) etching. Energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) proved the formation of oxygen-terminated nanostructures, which was ascribed to the oxygen plasma and the self-masking. The length of diamond nanotubes as well as the root diameter increased gradually and non-linearly with the increase of etching time. It was indicated by cyclic voltammetry (CV) analysis that the effective active area of the electrodes increased after etching, and variations of resulting reaction performance were observed. The oxygen-terminated and nanostructured BDD electrode obtained by etching with the optimized parameters features better electrocatalytic performance, with reduced oxidation potential and 46.8 % higher Faraday Efficiency (FE) for hydrogen peroxide production, compared to the original BDD sample. Therefore, the manufacturing of nanostructures is an effective method to improve the efficiency of BDD water oxidation for the production of hydrogen peroxide.

In-situ low-temperature sulfur CVD on metal sulfides with SO2 to realize self-sustained adsorption of mercury

Capturing gaseous mercury (Hg0) from sulfur dioxide (SO2)-containing flue gases remains a common yet persistently challenge. Here we introduce a low-temperature sulfur chemical vapor deposition (S-CVD) technique that effectively converts SO2, with intermittently introduced H2S, into deposited sulfur (Sd0) on metal sulfides (MS), facilitating self-sustained adsorption of Hg0. ZnS, as a representative MS model, undergoes a decrease in the coordination number of Zn–S from 3.9 to 3.5 after Sd0 deposition, accompanied by the generation of unsaturated-coordinated polysulfide species (Sn2–, named Sd*) with significantly enhanced Hg0 adsorption performance. Surprisingly, the adsorption product, HgS (ZnS@HgS), can serve as a fresh interface for the activation of Sd0 to Sd* through the S-CVD method, thereby achieving a self-sustained Hg0 adsorption capacity exceeding 300 mg g−1 without saturation limitations. Theoretical calculations substantiate the self-sustained adsorption mechanism that S8 ring on both ZnS and ZnS@HgS can be activated to chemical bond S4 chain, exhibiting a stronger Hg0 adsorption energy than pristine ones. Importantly, this S-CVD strategy is applicable to the in-situ activation of synthetic or natural MS containing chalcophile metal elements for Hg0 removal and also holds potential applications for various purposes requiring MS adsorbents.