Conductive Diamond Research Articles

(Invited) Electrochemical Characteristics of Diamond Films for Neural Devices

Robust electrode technology is essential to address the growing demand for neural devices for sensing and stimulation in the central and peripheral nervous system. Difficulties remain in device performance, mechanical integrity and stability. Conductive diamond is highly promising to overcome these obstacles, and provides the opportunity to integrate sensing and stimulation in the same robust device. This presentation focuses on our diamond-film electrode development and application for neurosensing and for stimulation of neural activity. Unique fabrication and materials integration approaches have been used to obtain diamond electrodes in a flexible construct; one example is diamond-on-polymer electrode arrays.

Wastewater Disinfection Using Potential Switching Methods on Boron Doped Ultrananocrystalline Diamond Electrodes

Boron-doped diamond (BDD) has attracted considerable attention as an electrode material used for electrochemical disinfection of wastewater, due to its high oxygen evolution over-potential.[1], [2] This property enables the formation of highly reactive oxygen species (ROS) such as hydroxyl radicals, ozone, and hydrogen peroxide.[3]–[6] Despite the promise of BDD as a liquid disinfection electrode, there is little information in literature that details the optimal conditions for ROS generation. Effects of potential switching for inhibiting fouling of the electrode surface, evolving surface chemistry, and resultant energy efficiency in sanitizing wastewater are not widely reported. Knowledge of these conditions and their liquid disinfection properties would allow production of ROS with higher efficiency and therefore lower cost in real-world applications. The present work investigates the generation of ROS and subsequent liquid disinfection of wastewater using as-grown boron-doped ultrananocrystalline diamond (BD-UNCD) electrodes. Static and potential switching methods of generating ROS are compared to determine their effects on liquid disinfection, chlorine generation, energy expenditure, electrode fouling, and electrode surface chemistry. These results build on an evolving understanding of the electrochemical generation of ROS from BDD electrodes. Our results show that liquid disinfection of diluted wastewater can occur with negligible chlorination and efficient energy expenditure using potential switching methods. Comparison of potential switching to static potential methods show differences in energy expenditure, chlorination, and electrode scaling; as well as time needed for disinfection of liquid waste. It is proposed that the electrogeneration of functional groups at oxidative potentials of BD-UNCD allows for an increased current density during the successive electrolysis at reductive potentials, and that this electrogeneration correlates to an enhanced production of H2O2. Through potential switching, these functional groups can be stabilized and used continuously to more efficiently produce H2O2, and potentially other ROS, when compared to static potential methods at these same potentials by optimizing the applied potentials and duty cycle. Moreover, potential switching has been previously used to inhibit electrode fouling,[7]–[10] which is commonplace in liquid waste sanitation, and therefore offers a practical method for electrochemical disinfection of wastewater in large scale applications.

Surface Redox Chemistry of Immobilized Nanodiamond: Effects of Particle Size and Electrochemical Environment

The size of the diamond particle is tailored to nanoscale (nanodiamond, ND), and the ND surface is engineered targeting specific (electrochemical and biological) applications. In this work, we investigated the complex surface redox chemistry of immobilized ND layer on conductive boron-doped diamond electrode with a broad experimental parameter space such as particle size (nano versus micron), scan rate, pH (cationic/acidic versus anionic/basic), electrolyte KCl concentration (four orders of magnitude), and redox agents (neutral and ionic). We reported on the significant enhancement of ionic currents while recording reversible oxidation of neutral ferrocene methanol (FcMeOH) by almost one order of magnitude than traditional potassium ferricyanide (K3Fe(CN)6) redox agent. The current enhancement is inversely related to ND particle diameter in the following order: 1 μm << 1000 nm < 100 nm < 10 nm ≤ 5 nm < 2 nm. We attribute the current enhancement to concurrent electrocatalytic processes, i.e. the electron transfer between redox probes and electroactive surface functional (e.g. hydroxyl, carboxyl, epoxy) moieties and the electron transfer mediated by adsorbed FcMeOH+ (or Fe(CN)63+) ions onto ND surface. The first process is pH dependent since it depends upon ND surface functionalities for which the electron transfer is coupled to proton transfer. The adsorption mediated process is observed most apparently at slower scan rates owing to self-exchange between adsorbed FcMeOH+ ions and FcMeOH redox agent molecules in diffusion-limited bulk electrolyte solution. Alternatively, it is hypothesized that the surface functionality and defect sites (sp2-bonded C shell and unsaturated bonds) give rise to surface electronic states with energies within the band gap (midgap states) in undoped ND. These surface states serve as electron donors (and acceptors) depending upon their bonding (and antibonding) character and, therefore, they can support electrocatalytic redox processes in the presence of specific redox-active molecules via feedback mechanism. Apparently, FcMeOH+ tended to have electrostatic affinity for negatively charged ND surface functionalities, corroborated by present experiments. We also attempted to study biocatalytic process using model metalloprotein (cytochrome c; Cyt c) immobilized on ND particles for investigating interfacial electron transfer kinetics and compared with those of functionalized graphene (graphene oxide; GO and reduced GO). The findings are discussed in terms of interplay of sp3-bonded C (ND core) and sp2-bonded C (ND shell and graphene-based systems).

Synthesis and characterization of boron doped diamond/β-SiC composite films

Boron doped diamond/β-SiC composite films with a conductive diamond phase separated by the insulating β-SiC phase are fabricated by the microwave plasma chemical vapor deposition process. By manipulating the gas phase composition during the film deposition, the boron incorporation and diamond/β-SiC ratio in the composite film are well controlled. Scanning electron microscopy, transmission electron microscopy, Raman and X-ray diffraction measurements are carried out to study the structural composition of the films. It is observed that the introduction of boron during the growth process does not affect the independent growth of diamond and β-SiC crystals with high crystal quality. Scanning spreading resistance microscopy measurements confirm the presence of the conductive diamond phase and the insulating β-SiC phase in the film. The observed differences in the conductivities between diamond and β-SiC are explained by the different boron acceptor levels in diamond and β-SiC crystals. Cyclic voltammetry measurements are carried out to study the electrochemical property of the films. Our results demonstrate that boron doped diamond/β-SiC composite films are a good candidate for electroanalysis applications whereby exploiting diamond's high chemical and dimensional stability as well as its excellent electrochemical properties.

Structural properties of highly conductive ultra-nanocrystalline diamond films grown by hot-filament CVD

In this work we show the correlation of the electrical conductivity of ultra-nanocrystalline (UNCD) diamond films grown by hot filament chemical vapor deposition (HFCVD) with their structural properties. The substrate temperature, the methane to hydrogen ratio and the pressure are the main factor influencing the growth of conductive UNCD films, which extends from electrical resistive diamond films (&amp;lt;10-4 S/cm) to highly conductive diamond films with a specific conductivity of 300 S/cm. High-resolution-transmission-electron-microscopy (HRTEM) and electron-energy-loss-spectroscopy (EELS) have been done on the highly conductive diamond films, to show the origin of the high electrical conductivity. The HRTEM results show random oriented diamond grains and a large amount of nano-graphite between the diamond crystals. EELS investigations are confirming these results. Raman measurements are correlated with the specific conductivity, which shows structural changes of sp2 carbons bonds as function of conductivity. Hall experiments complete the results, which lead to a model of an electron mobility based conductivity, which is influenced by the structural properties of the grain boundary regions in the ultra-nanocrystalline diamond films.

Conductive Diamond Powder Ink as a Functional Electrode Material

Conductive Diamond Powder Ink as a Functional Electrode Material

Electrochemical mineralization of cephalexin using a conductive diamond anode: A mechanistic and toxicity investigation

The contamination of surface and ground water by antibiotics is of significant importance due to their potential chronic toxic effects to the aquatic and human lives. Thus, in this work, the electrochemical oxidation of cephalexin (CEX) was carried out in a one compartment filter-press flow cell using a boron-doped diamond (BDD) electrode as anode. During the electrolysis, the investigated variables were: supporting electrolyte (Na2SO4, NaCl, NaNO3, and Na2CO3) at constant ionic strength (0.1 M), pH (3, 7, 10, and without control), and current density (5, 10 and 20 mA cm−2). The oxidation and mineralization of CEX were assessed by high performance liquid chromatography, coupled to mass spectrometry and total organic carbon. The oxidation process of CEX was dependent on the type of electrolyte and on pH of the solution due to the distinct oxidant species electrogenerated; however, the conversion of CEX and its hydroxylated intermediates to CO2 depends only on their diffusion to the surface of the BDD. In the final stages of electrolysis, an accumulation of recalcitrant oxamic and oxalic carboxylic acids, was detected. Finally, the growth inhibition assay with Escherichia coli cells showed that the toxicity of CEX solution decreased along the electrochemical treatment due to the rupture of the β-lactam ring of the antibiotic.

Irradiated-assisted electrochemical processes for the removal of persistent pollutants from real wastewater

Abstract In this work, it is studied the treatment of real wastewater (intensified with two target compounds) using electro-irradiated technologies. Two types of effluents coming from an organic-synthesis pharmaceutical industry and the outlet of a municipal wastewater treatment plant were intensified with metoprolol (β-blocker) and caffeine (stimulant), respectively. Conductive diamond electrochemical oxidation (CDEO), photolysis, sonolysis and all possible combinations among these technologies were evaluated for the treatment of both wastes. Results demonstrate that complete oxidation of the target compounds, as well as mineralization of the organic compounds contained in the matrixes, can be attained by all electro-irradiated technologies and no salt addition was needed to obtain an efficient treatment. Single irradiated technologies were inefficient in the oxidation but their combination with CDEO improves significantly the efficiency of the process showing clear synergistic effects. However, due to the large energy requirement of ultrasound irradiation, this combination is only cost-effective in the case of ultraviolet irradiation.

Boron-Doped Diamond-Film-Based Two-Dimensional Electrode of Electrophoresis Tank**Supported by the National Natural Science Foundation of China under Grant No 51472105, and the Key Program in Science and Technology of Jilin Province under Grant No 20150204062GX.

Chemically robust conductive p-type boron-doped diamond (BDD) films are an important electrode material and have been widely applied in electrochemistry. In this study, BDD films are taken as a two-dimensional (2D) electrode in a electrophoresis tank system instead of the conventional one-dimensional platinum wire electrode. The theoretical simulations by finite element numerical analysis reveal that the 2D BDD electrodes have relatively high intensity and uniformity of electric field in the tank. Experimentally, the 2D BDD electrodes with smaller size show excellent properties for the separation of DNA fragments. The advantages of the 2D BDD electrodes with chemical inertness, sustainability, high intensity and uniformity electronic field, as well as reduced small size of electrophoresis tank would open a possibility for realizing new generation, high-performance biological devices.

Toward highly conductive n-type diamond: Incremental phosphorus-donor concentrations assisted by surface migration of admolecules

The realization of low-resistance n-type diamond is required to form novel semiconducting devices. However, heavily doping with phosphorous, the most suitable electron donor, remains challenging. Here we demonstrate that the phosphorus incorporation efficiency in deposited diamond can be maximized when using the largest possible terrace width of vicinal {111}-substrates. Given step-flow-predominant crystal growth, the greater surface migration length of phosphorus-containing admolecules compared with those of carbon-containing parent species explain this. With our findings we create a model which provides a complementary perspective to explain large fluctuations in dopant incorporation efficiencies for p-type and n-type diamond. Our model can also explain conflicting models for admolecule motion responsible for diamond crystallization.

Nanocrystalline Diamond Integration with III-Nitride HEMTs

Reduced performance in Gallium Nitride (GaN)-based high electron mobility transistors (HEMTs) as a result of self-heating has been well-documented. To mitigate this effect, the incorporation of high thermal conductivity diamond heat spreading films or substrates has been proposed. A mid-process integration scheme, termed “gate-after-diamond,” is shown to improve the thermal budget for NCD deposition and enables scalable, large-area diamond coating without degrading the Schottky gate metal. The optimization of this process step is presented in this work. Nanocrystalline (NCD)-capped devices had a 20% lower channel temperature at equivalent power dissipation. Improved electrical characteristics were also observed, notably improved on-resistance and breakdown voltage, and reduced gate leakage.

Piezoresistivity of n-type conductive ultrananocrystalline diamond

Recent developments of a piezoresistive sensor prototype based on n-type conductive ultrananocrystalline diamond (UNCD) are presented. Samples were deposited using hot filament chemical vapor deposition (HFCVD) technique, with a gas mixture of H2, CH4 and NH3, and were structured using multiple photolithographic and etching processes. Under controlled deposition parameters, UNCD thin films with n-type electrical conductivity at room temperature (5×10−3–5×101S/cm) could be grown. Respective piezoresistive response of such films was analyzed and the gauge factor was evaluated in both transverse and longitudinal arrangements, also as a function of temperature from 25°C up to 300°C. Moreover, the gauge factor of piezoresistors with various sheet resistance values and test structure geometries was evaluated. The highest measured gauge factor was 9.54±0.32 at room temperature for a longitudinally arranged piezoresistor with a sheet resistance of about 30kΩ/square. This gauge factor is well comparable to that of p-type boron doped diamond; however, with a much better temperature independency at elevated temperatures compared to the boron-doped diamond and silicon. To our best knowledge, this is the first report on piezoresistive characteristics of n-type UNCD films.

Effect of Boron Doping on the Wear Behavior of the Growth and Nucleation Surfaces of Micro- and Nanocrystalline Diamond Films.

B-doped diamond has become the ultimate material for applications in the field of microelectromechanical systems (MEMS), which require both highly wear resistant and electrically conductive diamond films and microstructures. Despite the extensive research of the tribological properties of undoped diamond, to date there is very limited knowledge of the wear properties of highly B-doped diamond. Therefore, in this work a comprehensive investigation of the wear behavior of highly B-doped diamond is presented. Reciprocating sliding tests are performed on micro- and nanocrystalline diamond (MCD, NCD) films with varying B-doping levels and thicknesses. We demonstrate a linear dependency of the wear rate of the different diamond films with the B-doping level. Specifically, the wear rate increases by a factor of 3 between NCD films with 0.6 and 2.8 at. % B-doping levels. This increase in the wear rate can be linked to a 50% decrease in both hardness and elastic modulus of the highly B-doped NCD films, as determined by nanoindentation measurements. Moreover, we show that fine-grained diamond films are more prone to wear. Particularly, NCD films with a 3× smaller grain size but similar B-doping levels exhibit a double wear rate, indicating the crucial role of the grain size on the diamond film wear behavior. On the other hand, MCD films are the most wear-resistant films due to their larger grains and lower B-doping levels. We propose a graphical scheme of the wear behavior which involves planarization and mechanochemically driven amorphization of the surface to describe the wear mechanism of B-doped diamond films. Finally, the wear behavior of the nucleation surface of NCD films is investigated for the first time. In particular, the nucleation surface is shown to be susceptible to higher wear compared to the growth surface due to its higher grain boundary line density.

Surface Treatment of Boron Doped Diamond Using Atmospheric-Pressure Nitrogen Plasma Jet

Conductive boron-doped diamond (BDD) exhibits high physical and chemical stability, a wide potential window, a low background current. Owing to the typical characters, BDD is expected for use as an electrode material in the electrochemical applications such as electrolysis, waste water treatment, pH sensing, and electroanalysis. In order to further functionalize BDD, the surface treatment technique, e.g., enlargement the surface (reaction) area, control the morphology, chemical functionalization, is required and several kinds of the treatment method have been attempted including catalytic etching, oxygen treatment and so-on. We attempted to use atmospheric-pressure nitrogen plasma jet (APN2PJ) for the surface treatment of BDD for the first time. APN2PJ is a unique technique and can generate NH and nitrogen radicals at high density even under atmospheric pressure. In this presentation, the effects of APN2PJ on the chemical as well as electrochemical properties of BDD, especially the electrochemical double layer capacitance and the behavior at high potential region up to 2.5 V vs. RHE, are reported. In addition, the effect of following ultrasonic treatment is also reported. BDD electrode (De Nora Permelec Ltd., Nb substrate, thickness of BDD layer = 2.5 mm, boron content = 9.000 ppm) was used as purchased. APN2PJ treatment was carried out original apparatus. The treatment time was restricted at 3, 5 and 7 minutes. Mixture gas of nitrogen and hydrogen was used as the atmospheric gas. The applied voltage and pulse current of APN2PJ was set at 5 kV and 1 A, respectively. Hereafter, BDD without APN2PJ treatment is denoted as BDD-0 and BDD after plasma treatment as BDD-(APN2PJ treatment time). After APN2PJ treatment, the morphology of BDD was observed by FE-SEM and the chemical analysis was carried out by XPS. Cyclic voltammetry was carried out in a three-electrode electrochemical cell under nitrogen atmosphere. A gold mesh and Ag|AgCl electrode was used as the counter electrode and the reference electrode. 0.5 mol dm-3 H2SO4 aqueous solution was used as the electrolyte. The electrochemical double layer capacitance of each BDD electrodes was estimated in the potential region between 0.5 V and 0.6 V vs. RHE. Figure 1 a) and b) shows FE-SEM images of BDD-0 and BDD-7. The surface of BDD-0 was consisted by tiny single crystals of BDD of several micrometer sizes. On the other hand, many boundary (grooves), pits and the granular precipitates were clearly observed on the surface of BDD-7, which shows APN2PJ treatment gives morphology change of the surface of BDD. From XPS analysis, the peaks were observed in the spectra of C1s, O1s and N1s for each BDD electrodes after APN2PJ treatment, although only C1s peak was observed for BDD-0. In particular, in N1s XP spectra of BDD electrodes after APN2PJ treatment, four peak components assigned to Nitride, N-C sp3 bond, N-C sp2 bond and N-O bond were observed, showing that nitrogen was introduced into BDD surface and simultaneously, the morphology change as shown in Fig 1 b) was taken place. We also investigated the effects of following ultrasonic treatment. This was carried out in pure water. Figure 1 c) shows FE-SEM image of BDD-7 following ultrasonic treatment. Here, thus BDD was named as U-BDD-(APN2PJ treatment time). The granular precipitates, which are observed on the surface of BDD-7 (Fig. 1 b)), were disappeared and the grooves and holes became to be clearly observed. The electrochemical double layer capacitance was increased with an increase in APN2PJ treatment time and was further increased by following ultrasonic treatment. If we assumed that the capacitance relates to the geometric surface area of the electrode, the surface area of BDD would be increased with appearance of the grooves and the pits by APN2PJ. Furthermore, it was reasonably considered that the ultrasonic treatment gives disappearance of the precipitates as well as cleaning of the surface, which would lead to increase in the capacitance (surface area). The behavior at high potential region will be also presented. Figure 1

(Invited) Electrically Conductive Diamond Membrane for Electrochemical Separation Processes

Boron-doped diamond has been applied as an outstanding electrode material for electrochemical applications. Using templated growth techniques, a variety of diamond nanostructures like diamond wires and diamond foams can be fabricated [1, 2]. Using quartz or glass fiber paper as growth templates, porous diamond membranes are fabricated [3]. Compared to polymer membranes or membranes based on sp2 carbons, diamond membranes can survive in aggressive media and high temperature conditions. Also, the ion selectivity can be controlled by surface terminations as well as the bias potential of the membrane. Therefore, this kind of membranes is very promising for the electrochemical separation processes such as desalination, pollutants concentration and protein separation. However, both the fabrication and application of diamond membranes are so far reported only in very limited cases. In this paper, we report our recent progress with respect to the templated diamond growth using quartz fiber paper as the growth template [3]. With optimized microwave CVD growth, nanocrystalline diamond film is fully coated onto the quartz fiber as has been confirmed via SEM. The growth conditions in terms of temperature, methane concentration and boron/carbon ratio are investigated in detail. The diamond quality is evaluated via Raman spectroscopy. The potential window of the diamond membrane is determined via cyclic voltammetry in an aqueous NaClO4 solution to be over 3 V. By applying potential to the membrane, reactive ions will accumulate inside the membrane and change its porosity. As a result, the ion flux through the membrane can be well tuned. This ion selectivity can be used to separate charged molecules. As a proof of concept, Rhodamine B, Ni2+ and Cu2+ are separated by the diamond membrane under different biases. Finally, due to the robustness of diamond, the membrane can be cleaned via a high potential (+2 V vs Ag/AgCl) oxidation process in situ. Metal deposits and organic contaminants are proved to be removable by this method. Therefore, this membrane is also suitable for applications where only simple in-situ maintenances are possible. This project has received funding from the European Union's Horizon 2020 Programme under Grant Agreement no. 665085 (DIACAT). [1] Gao F, Wolfer MT, Nebel CE. Highly porous diamond foam as a thin-film micro-supercapacitor material. Carbon. 2014;80(0):833-40. [2] Gao F, Lewes-Malandrakis G, Wolfer MT, Muller-Sebert W, Gentile P, Aradilla D, et al. Diamond-coated silicon wires for supercapacitor applications in ionic liquids. Diamond Relat Mater. 2015;51:1-6. [3] Gao F, Nebel CE. Diamond-Based Supercapacitors: Realization and Properties. ACS Appl Mater Interfaces. 2015.

Scale-up of electrolytic and photoelectrolytic processes for water reclaiming: a preliminary study.

This work focuses on the scale-up of electrochemical and photoelectrochemical oxidation processes with diamond anodes for the removal of organic pollutants and disinfection of treated urban wastewater, two of the most important parameters for the reclaiming of wastewater. The removal of organics was studied with actual biologically treated urban wastewater intensified with 100mgdm(-3) of caffeine, added as a trace organic pollutant. The disinfection was also studied with biologically treated urban wastewater, and Escherichia coli was used to monitor the efficiency of the process. Results obtained with a single DiaCell® 101 were compared with those obtained with a single-stack DiaCell® 1001 and with a pilot plant made up of five of these stacks. Results obtained demonstrate that scale-up is not a simple but a very complex process, in which not only the electrode and the irradiation dose are important but also mass transfer conditions. Enhanced mass transport conditions have a determining and very positive effect on the removal of organics and a negative effect on the disinfection. Likewise, ultraviolet (UV) irradiation affects in a different way in the different setups used, having a great influence on the removal of complex organics and on the speciation of oxidants produced during disinfection. This works helps to understand the key differences observed in the scale-up, and it is a first approach for future works focused on the real application of conductive diamond electrochemical oxidation.

Electrically Conductive Diamond Membrane for Electrochemical Separation Processes.

Electrochemically switchable selective membranes play an important role in selective filtration processes such as water desalination, industrial waste treatment, and hemodialysis. Currently, membranes for these purposes need to be optimized in terms of electrical conductivity and stability against fouling and corrosion. In this paper, we report the fabrication of boron-doped diamond membrane by template diamond growth on quartz fiber filters. The morphology and quality of the diamond coating are characterized via SEM and Raman spectroscopy. The membrane is heavily boron doped (>10(21) cm(-3)) with >3 V potential window in aqueous electrolyte. By applying a membrane potential against the electrolyte, the redox active species can be removed via flow-through electrolysis. Compared to planar diamond electrodes, the ∼250 times surface enlargement provided by such a membrane ensures an effective removal of target chemicals from the input electrolyte. The high stability of diamond enables the membrane to not only work at high membrane bias but also to be self-cleaning via in situ electrochemical oxidation. Therefore, we believe that the diamond membrane presented in this paper will provide a solution to future selective filtration applications especially in extreme conditions.

Platinum–carbon electrocatalytic composites via liposome-directed electrodeposition at conductive diamond

A Pt precursor was entrapped in phosphatidylcholine-cholesterol vesicles and the liposomal suspension was used for direct electrodeposition of a Pt-based catalyst on boron-doped diamond (BDD). The average size of the deposited particles (ca. 15 to ca. 40 nm) is closely related to that of the liposomes and Pt particles are partially embedded into a carbonaceous matrix. Methanol anodic oxidation was used for gauging the electrocatalytic activity of the composites and it was found that the electrodeposition with prior adsorption of the liposomes enables more efficient use of platinum. Without preliminary adsorption, a much higher resistance to fouling was observed for the electrocatalyst. This behavior was ascribed to the presence on the electrodes surface of PtO2 and of a higher amount of oxygenated carbon states. These species act as oxygen donors contributing to an easier eviction of the adsorbed CO, thus partially regenerating active sites from the electrocatalyst surface.

Long-Life Silicon/Graphite Anode with Nano Carbon Coatings for Lithium Ion Battery - Graphene Nanowalls and Nitrogen Incorporated Ultrananocrystalline Diamond

Although lithium ion batteries (LIBs) have been used in many consumer and industrial products, the energy storage capacity per volume/weight and the battery cycling lifetime have much room for further improvement. This is especially challenging for high demanding applications such as long-range electric vehicles, and smart grid renewable energy storage. Among LIB anode materials, graphite is the most common one in the market today. Many novel anode materials have been studied in pursuit of much higher battery energy storage capacity for a given volume and weight. Among them, silicon is the most attractive one which theoretically is capable of storing more than ten times of energy than that of graphite anode for the same anode weight. However, silicon suffers from extensive volume expansion and shrinkage by about 400% when it cycles through fully charged and discharged states. The volume difference leads to breakage of silicon particles and the loss of their electrical contacts to the current collector and thus its capability of further discharging and charging. On the other hand, graphite has a layered structure, which suffers from breakage between adjacent layers into smaller pieces and thus possibly loses the capability of broken apart small graphite pieces in charging and discharging. Therefore, technologies for preventing aforementioned huddles against achieving long-life and high-capacity LIBs are highly desirable. Novel electrically conductive ultrananocrystalline diamond, graphene nanowalls, and diamond-graphene hybrid nano-carbon coatings have been applied by plasma enhanced chemical vapor deposition technique to graphite and silicon based LIB anodes and achieved much longer cycling lifetime compared to those without such nano carbon coatings. This paper will present the nano-carbon coating processes, materials characterization, LIB fabrication processes, and the characterization of LIB half cells which demonstrates enhance lifetime and charge storage capacity.

Use of conductive diamond photo-electrochemical oxidation for the removal of pesticide glyphosate

Abstract In this work, the depletion of a commercial formulation of the pesticide glyphosate (RoundUp) using photolysis, electrolysis and photo-electrolysis with diamond anodes was studied. Results show that single photolysis is an inefficient technology for the removal of the pesticide; however, when coupled with electrolysis the removal yield significantly improves. The use of a combined process (photo-electrolysis) leads to the generation of higher concentrations of free radicals from the photo-activation of the oxidants electrogenerated. A major finding is that the supporting electrolyte plays a key role on the removal of glyphosate due to the generation of different oxidant species. Such species (peroxocarbonates, peroxosulfates and hypochlorite) also contribute to the depletion of the pesticide. Furthermore, the removal of glyphosate is clearly influenced by the current density because of the strong relationship between this parameter and the oxidants produced on the anode surface.