The effect of boron doping into Co-C-N and Fe-C-N electrocatalysts on the oxygen reduction reaction

Co-C-N and Fe-C-N thin film catalysts have been modified by controlled doping with boron. Corresponding novel thin film catalysts Co-C-N-B and Fe-C-N-B were synthesized by combinatorial magnetron sputter deposition in an Ar/N₂ gas mixture followed by subsequent heat-treatment between 700 and 1000 °C in an argon atmosphere. The nitrogen content of the as-prepared thin film catalysts could be increased by the addition of boron. Furthermore, the amount of remaining nitrogen in heat-treated catalyst samples was significantly higher in case of boron containing samples. The thin film catalysts were characterized by means of X-ray diffraction (XRD) analysis, electron microprobe and electrochemical measurements. For electrochemical studies the activity as oxygen reduction reaction (ORR) catalyst was investigated using the rotating ring-disk electrode (RRDE) technique in 0.1 M HClO₄ solution at room temperature. The catalytic activity was found to decrease with the boron content in the thin film catalysts even though the N-content increased.     

Influence of sputtering power on oxygen reduction reaction activity of zirconium oxides prepared by radio frequency reactive sputtering

Zirconium oxides (ZrO_2−x) have been investigated as new cathodes for direct methanol fuel cells without platinum. ZrO_2−x films were prepared using a radio frequency (RF) magnetron sputtering at RF powers from 75 to 175 W. The influence of the RF power on the catalytic activity for the oxygen reduction reaction (ORR) and properties of the ZrO_2−x films were examined. The ORR activity of the ZrO_2−x catalyst increased with the RF power in the range we studied. The onset potential for ORR over ZrO_2−x deposited at 175 W was 0.88 V vs RHE. In addition, the relationship between the ORR activity and the composition, crystallinity, electric conductivity, as well as the ionization potential has been investigated. The zirconium oxide with an oxygen defected state and the higher electric conductivity showed the higher ORR activity, and the electrocatalytic activity for ORR increased with the decreasing in the ionization potential of the ZrO_2−x catalyst.     

Effects of Sputtering and Plasma Etching on the Surface Reactivity of Graphite

The surfaces of highly oriented pyrolytic graphite (HOPG) samples were treated using two different methods, exposure to an energetic oxygen ion beam and immersion in an oxygen ion plasma, and the reactions which occur during treatment were characterized using high-resolution electron energy loss spectroscopy (HREELS), temperature programmed desorption (TPD), and scanning tunneling microscopy (STM). Both surface treatments result in similar oxidation species. The results of this investigation provide spectroscopic evidence for the presence of semiquinone functionalities on sputtered and oxidized HOPG. STM images are presented to quantify the increase in defect sites after oxygen ion sputtering and to correlate defect site density with reactivity.     

Highly Durable Platinum based Cathode Electrocatalysts for PEMFC Application using Oxygen and Nitrogen Functional Groups Attached Nanocarbon Supports

The combined effect of oxygen and nitrogen functional groups on highly crystalline carbon supports like multiwalled carbon nanotubes (MWCNT) and MWCNT‐few layer graphene hybrid structures (MWCNT+FLG) have been investigated towards oxygen reduction reaction (ORR) performance and carbon corrosion durability in polymer electrolyte membrane fuel cell (PEMFC) applications. The pristine carbon supports were modified with oxygen and nitrogen functionalities by treating with concentrated mineral acids and subsequent nitrogen plasma treatment assisted with R.F. magnetron sputtering. Pt nanoparticles were dispersed over these chemically modified carbon supports by polyol reduction method. The physicochemical properties of as synthesized electrocatalysts were studied by different techniques such as XRD, TEM, FTIR, Raman and XPS. Electrochemical properties were investigated by cyclic voltammetry and linear sweep voltammetry in 0.1M HClO₄ medium. Compared to commercial Pt/C catalysts, durability show ∼30 % enhancement for the as prepared electrocatalysts due to the presence of large amount of pyrrolic nitrogen and highly oriented graphitic nature of the catalyst supports. The ORR performance were comparable with Pt/C (TEC10E30E) in terms of MSA, 259, 270, 252 A g⁻¹ for Pt/C, Pt/N‐f‐MWCNT, Pt/N‐f‐(MWCNT+FLG) respectively.     

A dual metal-organic framework strategy for synthesis of FeCo@NC bifunctional oxygen catalysts for clean energy application

Developing high efficient bifunctional oxygen electrocatalysts for clean energy applications like Zin-air battery (ZAB) is highly desired, because it would reduce the cost and speed up the practical application of ZAB. Here we use a dual metal–organic framework (MOF) synthesis strategy to prepare the N-doped carbon supported bimetallic FeCo nanoparticle catalysts (marked as FeCo@NC) by pyrolysis of ZnCo-ZIF/MIL-101(Fe) composite. The FeCo@NC exhibits remarkable electrocatalytic activity for ORR with half-wave potential of 0.89 V vs. the reversible hydrogen electrode (RHE) and robust durability for both ORR and OER (oxygen reduction reaction and oxygen evolution reaction), which is attributed to the generation of Fe_0.26Co_0.74 crystalline phase and mesopores due to the dual-MOF synthesis strategy. The rechargeable ZAB based on FeCo@NC air electrode shows a maximum energy density of 139.6mW·cm^-2 and excellent cyclic stability over 130 h, significantly surpassing the Pt and Ir-based ZAB. The present work provides a useful dual-MOF synthesis strategy for preparing high-performance multifunctional catalysts for ORR, OER and hydrogen evolution reaction (HER).     

Frequency-Dependent Dielectric Parameters of Au/TiO2/n-Si (MIS) Structure

Silicon - In this study, thin film of titanium dioxide (TiO2) was deposited onto n-type silicon substrate by radio frequency (RF) magnetron sputtering system. The admittance (capacitance and...     

Resistive switching characteristics of sputtered AlN thin films

AlN thin films were deposited on Pt/Ti/SiO₂/Si substrates using a radio-frequency magnetron sputtering technique. The effect on the switch current–voltage characteristics of four different materials in the electrode fabricated on top of the AlN film was investigated. The deposition time and nitrogen content in the sputtering atmosphere were changed to adjust the thickness and composition of the AlN thin films, respectively. The influence of film thickness and content on the resistive switching behavior was discussed. The possible mechanism of resistive switching was examined via analyses of the electrical resistive switching characteristics, forming voltage, and on/off current ratio.     

氧电极金属单原子催化剂的研究进展

燃料电池和金属-空气电池作为目前最具发展前景的能量转换和储存设备,对于缓解人类发展所面临的能源与环境问题大有裨益。然而,较差的氧电极反应,如燃料电池中的氧还原反应以及锌空电池中的氧还原及析氧反应,却限制着这两类装置的高效运行。近年来,人们提出了利用单原子催化剂（SACs）来提高氧电极反应的反应动力学。因此,针对两类氧电极反应,本综述根据构成活性位点的不同金属元素进行了分类总结,重点关注了各类催化剂的共性及进展。同时,还对具有双功能的催化剂及其在锌空电池的应用进行了总结。最后,针对SACs目前存在的问题和未来的发展方向提出了建议,旨在为单原子氧电极催化剂的设计及发展指明道路。     

Advances in single-atom catalysts for oxygen electrodes

As the most promising energy conversion and storage devices, fuel cells and metal-air batteries are of great benefit in alleviating the energy and environmental problems. However, the sluggish oxygen electrode reactions, including oxygen reduction reaction (ORR) for fuel cell and ORR couple with oxygen evolution reaction (OER) for zinc-air batteries, seriously limit the efficient of both types of devices. In recent years, single-atoms catalysts (SACs) have been proposed to improve the kinetics of oxygen electrode reaction. Therefore, for these two types of oxygen electrode reactions, this review firstly summarized their possible mechanism. Then, the SACs were classified by the different metal elements for both ORR and OER. Thus, noble-metal-based and non-noble-metal-based catalysts have been summarized in these two reactions. At the same time, a summary of the dual-function catalyst and its application in zinc air batteries is also given. Finally, in view of the current problems and future development directions of SACs, suggestions are put forward, aiming to pave the way for the design and development of monoatomic oxygen electrode catalysts.     

Advances in single-atom catalysts for oxygen electrodes

As the most promising energy conversion and storage devices, fuel cells and metal-air batteries are of great benefit in alleviating the energy and environmental problems. However, the sluggish oxygen electrode reactions, including oxygen reduction reaction (ORR) for fuel cell and ORR couple with oxygen evolution reaction (OER) for zinc-air batteries, seriously limit the efficient of both types of devices. In recent years, single-atoms catalysts (SACs) have been proposed to improve the kinetics of oxygen electrode reaction. Therefore, for these two types of oxygen electrode reactions, this review firstly summarized their possible mechanism. Then, the SACs were classified by the different metal elements for both ORR and OER. Thus, noble-metal-based and non-noble-metal-based catalysts have been summarized in these two reactions. At the same time, a summary of the dual-function catalyst and its application in zinc air batteries is also given. Finally, in view of the current problems and future development directions of SACs, suggestions are put forward, aiming to pave the way for the design and development of monoatomic oxygen electrode catalysts.     

Non-platinum electrocatalysts: Manganese oxide nanoparticle-cobaltporphyrin binary catalysts for oxygen reduction

This study is concerned with the development of non-platinum electrocatalysts for the efficient 4-electron reduction of molecular oxygen to water in acidic media. A binary catalyst composed of electrodeposited manganese oxide nanoparticles (nano-MnO _x ) and cobalt porphyrin macro complex (CoP) has been proposed in. The modification of glassy carbon (GC) electrode with CoP alone resulted in a significant positive shift of the oxygen reduction reaction (ORR) compared to the unmodified GC electrode while maintining a 2-electron reduction. That is a positive shift of the onset potential of the ORR of ca. 450 mV was achieved at the former electrode. The modification of the GC electrode with nano-MnO _x alone did not affect the ORR peak potential, but caused a remarkable increase in the reduction peak current due to the catalytic disproportionation of the electrogenerated hydrogen peroxide into water and oxygen. The modification of a GC electrode with CoP and nano-MnO _x (utilizing the advantages of the individual catalysts) resulted in the occurrence of the ORR at a significantly positive potential with almost double peak current compared to the unmodified GC electrode, suggesting a promising procedure for developing electrocatalysts for oxygen reduction in replacement of costly Pt. XPS and SEM techniques were employed to probe the structural and morphological characterization of the proposed binary catalysts.     

锌-空气电池Co-PPy-C复合催化剂的电化学性能研究

采用化学氧化聚合法合成了以碳为载体的钴-聚吡咯(PPy)配合物Co-PPy-C,作为气体扩散电极的氧还原催化剂。利用极化曲线、交流阻抗、计时电流等电化学方法测试了其在碱性介质中(6 mol/L KOH)氧气气氛条件下氧还原的催化性能。电极电位在-0.20 V vs.Hg/HgO时,催化剂电流密度达到158 mA/cm2,显示出优越的氧还原电催化性能;采取催化层/集流体/气体扩散层的排布方式,以纯锌为负极,6 mol/L的KOH为电解液,将气体扩散电极与锌负极组装成锌-空气电池。电池以80 mA/cm2进行恒流放电,放电电压为1.0 V,且性能稳定。     

Electrical conductivity of textured Sm and Nd Co-doped CeO2 thin-film electrolyte

Nanocrystalline thin-film electrolytes of Sm³⁺ and Nd³⁺ co-doped ceria have been deposited on polycrystalline alumina substrates via RF magnetron sputtering. It is found that with the increase of substrate temperature from room temperature to 600 °C, the structure of the film varies from (1 1 1) preferred orientation to random orientation, accompanied by an enhancement in electrical conductivity. It is estimated that the activation energy for oxygen ion migration along (1 1 1) orientation may be higher than other crystal orientations, resulting in a lower conductivity of the (1 1 1) barrier textured co-doped ceria film electrolyte. It also indicates that the electrical conduction is predominantly due to the oxygen ions.     

Screen-printed carbon electrode modified on its surface with amorphous carbon nitride thin film: Electrochemical and morphological study

The surface of a screen-printed carbon electrode (SPCE) was modified by using amorphous carbon nitride (a-CN_x) thin film deposited by reactive magnetron sputtering. Scanning electron microscopy and photoelectron spectroscopy measurements were used to characterise respectively the morphology and the chemical structure of the a-CN_x modified electrodes. The incorporation of nitrogen in the amorphous carbon network was demonstrated by X ray photoelectron spectroscopy. The a-CN_x layers were deposited on both carbon screen-printed electrode (SPCE) and silicon (Si) substrates. A comparative study showed that the nature of substrate, i.e. SPCE and Si, has a significant effect on both the surface morphology of deposited a-CN_x film and their electrochemical properties. The improvement of the electrochemical reactivity of SPCE after a-CN_x film deposition was highlighted both by comparing the shapes of voltammograms and calculating the apparent heterogeneous electron transfer rate constant.     

Characteristics of Li–P–W–O–N electrolyte for all solid state electrochromic devices

A LiPON–WO₃ composite thin film (LPWON) was evaluated for use as a solid electrolyte in solid state electrochromic (EC) devices. LiPO₄ and a WO₃ (2 wt%) composite sputtering target was synthesized by a ball milling process. The LPWON thin films were deposited by RF magnetron sputtering in Ar + N₂ and N₂ atmospheres. The structural, electrochemical, and optical properties of the LPWON electrolytes were characterized by X-ray diffraction (XRD), UV–visible spectroscopy, and an impedance analyzer. EC mirrors with WO₃ (coloring layer), LPWON (solid electrolyte), and stainless steel (mirror electrode) on ITO (transparent electrode) glass were fabricated to analyze the improved EC properties due to the LPWON electrolyte. The LPWON may lead to electrolytes with more stable potential cycle properties.     

Investigation of heterostructure between diamond and iridium on sapphire

Diamond thin film has outstanding physical and chemical properties. Diamond-on-iridium configurations have been prepared by several methods, such as microwave enhanced plasma CVD, direct currency plasma CVD, and hot filament CVD. In this study, an Ir interlayer was deposited on single crystal sapphires (Al₂O₃) with A-planes {1120} by an RF magnetron sputtering method after annealing samples. In addition, a diamond thin film was deposited by a microwave enhanced plasma chemical vapor deposition (MPCVD) method using a mixture of hydrogen and methane gases after a bias enhanced nucleation (BEN) procedure.Ir (001) was grown on the A-plane of sapphire by X-ray pole figure measurement. Diamond thin films were synthesized on each Ir/sapphire substrate and characterized by SEM, Raman spectroscopy. D {100} faces were exhibited in substantial areas of diamond films, and a flat D {100} plane was partially obtained. It is considered that diamond thin films on Ir {100} were mainly grown towards the <100> direction and were epitaxially grown in part.     

Preparation and optical properties of W-doped VO2/AZO bilayer composite film

In order to improve its visible light transmittance, W-doped VO₂ thin film was prepared with direct current (DC) reactive magnetron sputtering on the surface of Al-doped ZnO (AZO) thin film deposited on quartz glass substrate in advance with radio frequency (RF) magnetron sputtering. The effects of sputtering power for AZO film were investigated on the crystal structures, surface morphologies and optical properties of AZO thin film and W-doped VO₂/AZO bilayer composite film. The results show that the crystallinity of both AZO monolayer film and the bilayer film first increases and then decreases with the increase of sputtering power. As the sputtering power increases, the film thickness increases. The integral visible luminous transmittance (T_lum) of the W-doped VO₂/AZO bilayer film decreases continuously, and the solar modulation efficiency (ΔT_sol) increases first and then decreases. When the sputtering power is 150 W, T_lum and ΔT_sol of W-doped VO₂/AZO bilayer film are 30.14% and 11.95%, 2.77% and 1.71% higher than those of W-doped VO₂ monolayer film, respectively.     

Effects of surface structure on the electrochemical properties of Nimetal complex oxide film electrode

Effects of surface structure on the electrochemical properties of Ni—metal complex oxide film electrodes prepared by radio frequency magnetron sputtering method and by thermal decomposition method have been investigated. Rotating disc electrode technique was applied to evaluate the electron transfer rate of the redox system [Fe(CN)₆]^3?/[Fe(CN)₆]^4? in 0.1 M NaOH solution. Dynamic impedance method to detect the impedance change of electrode/electrolyte interface and X-ray photoelectron spectroscopy were also used. The NiMo complex oxide film electrode prepared by rf magnetron sputtering method was found to have good stability, good reproducibility and effective electrochemical properties in comparison with the oxide film electrodes prepared by thermal decomposition method. Then, of the electrodes prepared by thermal decomposition method, the NiMo complex oxide film and the NiRe complex oxide film were shown to have good electrochemical properties. It was found by XPS analysis that both Mo ion at a higher oxidation state and oxygen influenced from this Mo ion, which showed clear occurrence for the NiMo oxide film prepared by rf sputtering method and no occurrence by thermal decomposition method, played a very important role in the reaction.     

Effect of ZnO seed layers on the solution chemical growth of ZnO nanorod arrays

High density ZnO nanorod arrays were grown on Si substrates coated with ZnO seed layers via aqueous solution route. The ZnO seed layers were deposited on the substrate using DC reactive sputtering and RF magnetron sputtering. It was found that ZnO seed layer with (1 0 3) preferred orientation, prepared using DC reactive sputtering, did not facilitate the formation of ZnO nanorods in the solution grown process. Prior seeding of the surface by ZnO layer with (0 0 2) preferred orientation, deposited using RF magnetron sputtering, leads to nucleation sites on which ZnO nanorod arrays can grow in a highly aligned fashion. ZnO nanorods with well-defined hexagonal facets (0 0 2) were grown almost vertically over the entire substrate. The uniformity and alignment of the nanorod arrays are strongly related to the properties of underneath ZnO seed layers.     

Titania Coatings on Polyethylene Terephthalate: Adhesion and XPS Studies

Titania coatings have been deposited on polyethylene terephtalate (PET) by the r.f. magnetron sputtering method in an oxygen-argon plasma from a titanium target and in a pure argon plasma from a titania target.

The dependence of the structural properties and the composition of the deposited films on the sputtering pressure and the r.f. power have been studied. In order to improve the adhesion strength between the titanium oxide films and their substrate, various cold plasmas are used to treat the polymer surface. These treatments' influence on the adhesion is studied by using the fragmentation test. The best results are obtained with a carbon dioxide plasma. The adhesion of the titania coating on the PET film also depends strongly on the deposition conditions. The highest values are reached when the titanium oxide films are deposited by the reactive sputtering process and when the elaboration parameters combine a total pressure as low as 0.8 Pa and a power density of 2.54 W cm^-2. The titania/PET interface, investigated by XPS, suggests the formation of Ti-O-C bonds in the first stage of the deposition of the titania films obtained by the reactive magnetron sputtering process, while no chemical reaction seems to occur between the PET and the titanium oxide film sputtered under a pure argon plasma.