Boron-doped Diamond Thin-film Electrodes Research Articles

Application of BDD thin film electrode for electrochemical decomposition of heterogeneous aromatic compounds

Abstract The aim of the presented study is to investigate the applicability of electrochemical oxidation of aromatic compounds containing heteroatoms, e.g. waste from production of pesticides or pharmaceutics, at a borondoped diamond (BDD) electrode. The BDD electrodes were synthesized by microwave plasma enhanced chemical vapour deposition (MW PE CVD). Investigation of the electrode surface by optical microscopy and scanning electron microscopy (SEM) confirmed that the synthesized layer was continuous and formed a densely packed grain structure with an average roughness of less than 0:5 μm. The influence of important electrochemical parameters: current density, kind of reactor, pH or mixing operation, on the efficiency of the oxidation was investigated. The fouling of electrode’s surface caused by the deposition of organic material was observed during CV and galvanostatic experiments. At low current density the oxidation rate constant k was low, but the current efficiency was relatively high. The BDD can be used successfully to remove heterogeneous aromatic compounds existing either as molecules or cations. During 4 h of electrolysis 95% of aromatic compounds were electrochemically decomposed to mineral forms. It was observed that the influence of the initial pH on mineralization was marginal.

Complementary Mechanism Model for the Electrochemical Mineralization

Comninellis and his research group have elucidated a theoretical model that permits us to predict the chemical oxygen demand (COD) and instantaneous current efficiency (ICE), during the electrochemical oxidation of organic pollutants on a synthetic boron-doped diamond thin film electrodes (BDD) in a batch recirculation system under galvanostatic conditions. Several studies highlight the good correlation between theoretical predictions and empirical data, but it was noted that some data, from some experiments, were not in agreement with the theoretical model, since it achieved efficiencies above 100%. Recently, few studies have reported phenomena that occur in electrocatalytic systems which were not deducted in the first models. Thus, we emphasize that the mineralization of organic compounds on BDD electrodes involves not only hydroxyl radicals but also the molecular oxygen present in air, in saturated aqueous solutions or strong oxidants generated from simultaneous reactions. Therefore, this highlights summarizes the results reported by other electrochemists until nowadays to understand the electrochemical oxidation mechanisms. Keywords: Dissolved oxygen, Hydroxyl radicals, Complementary mechanism model, Strong oxidant species, electrochemical oxidation, galvanostatic, organic pollutants, anode, hydroxyl radicals, biodegradable

Kinetic experiments of electrochemical oxidation of iohexol on BDD electrodes for wastewater treatment

Electrolysis of iohexol, an iodinated X-ray contrast medium, on synthetic boron-doped diamond (BDD) thin film electrodes was investigated for the first time. Kinetic experiments of electrochemical oxidation resulted in complete elimination of iohexol. Data from the kinetic experiments were compared against estimates by the kinetic model proposed previously by Comninellis et al. Excellent agreement between the experimental results and the kinetic model was observed. The results suggest that electrolysis on BDD electrodes is a promising method for the elimination of iohexol from wastewater.

Electrochemical treatment of wastewater containing chlorophenols using boron-doped diamond film electrodes

The electrochemical treatment of wastewater containing chlorophenols (2-monochlorophenol, 4-monochlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol) was carried out experimentally with synthetic boron-doped diamond (BDD) thin film electrodes. Current vs time curves under different cell voltages were measured. Removal rate of COD, instant current efficiency (ICE) and energy consumption were investigated under different current densities. The influence of supporting media is reported, which plays an important role in determining the global oxidation rate. The oxidative chloride is stronger than peroxodisulphate. The electrochemical characteristics of boron-doped diamond electrodes were investigated in comparison with active coating Ti substrate anode (ACT). The experimental results show that BDD is markedly superior to ACT due to its different absorption properties.

Dopamine Sensor Based on a Boron-Doped Diamond Electrode Modified with a Polyaniline/Au Nanocomposites in the Presence of Ascorbic Acid

A selective dopamine (DA) sensor was developed using gold nanoparticles (Au-NPs) dispersed overoxidized-polyaniline (PANI(ox)) based on a boron-doped diamond (BDD) thin-film electrode. The concentration of the DA was determined using voltammetry as a non-enzymatic sensor. BDD thin film has a high signal-to-noise ratio, a long-term stability, a high sensitivity, and a good reproducibility. PANI nanocomposites were directly synthesized on the BDD electrode and overoxidized using 0.5 M H(2)SO(4) solution. The overoxidized PANI film enhances selectivity and sensitivity toward DA. The Au-NPs were dispersed on the PANI nanocomposite by electrochemical deposition. The nanometer-sized Au-NPs favor the sensing of DA in the presence of ascorbic acid (AA). The combination of the PANI with the Au-NPs and the BDD electrode can create synergetic effects for the performance of the biosensor, such as a fast response time, a lower detection limit, a wider linear range, enhanced selectivity, and higher sensitivity for the determination of DA.

Condition optimization of amperometric determination of chemical oxygen demand using boron-doped diamond sensor

The amperometric determination of chemical oxygen demand (COD) reported by Quan Xie’s group (Electrochem Commun 9:2281, 14), was a rapid, green and simple COD evaluation method. This work focused on testing and verifying this method by using a home-made boron-doped diamond (BDD) film as anode and optimizing the experiment conditions. The BDD thin film electrode was employed as anode and the electrochemical process was run with different experimental parameters including counter electrode, electrode gap, applied potential, electrolyte pH, and temperature. Standard samples were determined in the optimum conditions, a linear range of 19.2–11,600 mg l−1 COD and a low detection limit of 0.192 mg l−1 COD were well established with the present approach. The COD value of the simulated organic wastewater determined by this method agreed well with the standard dichromate method, and it showed good accuracy, stability, and reproducibility.

Electrochemical Treatment of Wastewater Containing Chlorophenols Using Boron-Doped Diamond Film Electrodes

The electrochemical treatment of wastewater containing 2, 4, 6-trichlorophenol has been carried out experimentally with synthetic boron-doped diamond (BDD) thin film electrodes. Removal rate of COD, instant current efficiency (ICE) and energy consumption were investigated under different current density. The influence of supporting media is reported, which plays an important role in determining the global oxidation rate. The oxidative chloride is stronger than peroxodisulphate. The electrochemical characteristics of boron-doped diamond electrodes were investigated in comparison with active coating Ti substrate anode (ACT). The experimental results show that BDD is markedly superior to ACT due to its different absorption properties.

Electrolyte and Temperature Effects on the Electron Transfer Kinetics of Fe(CN)6–3/-4 at Boron-Doped Diamond Thin Film Electrodes

Cyclic and linear sweep voltammetry were used to investigate the effects of the electrolyte composition and temperature on the electron-transfer kinetics of Fe(CN)6–3/–4 at well-characterized, boron-doped diamond thin-film electrodes. Highly conductive films were employed, which were first cleaned of any adventitious nondiamond carbon impurity by a two-step chemical-oxidation, and subsequently hydrogenated in hydrogen microwave plasma. The apparent heterogeneous electron-transfer rate constant, k°app, depended on the electrolyte concentration and the electrolyte cation type, increasing in order of Li+ < Na+ < K+ < Cs+. However, the dependence of koapp on the electrolyte cation was less than the dependence observed for other electrodes, like glassy carbon and gold. For example, koapp at the 1.0 M concentration was only a factor of 1.6 greater in KCl than in LiCl for diamond. This is less than the factor of 5–10 seen for other electrodes, like glassy carbon and gold. The transfer coefficient for the oxidati...

Electrochemical Pretreatment of Wastewater from DDNP Production Using BDD Thin Film Electrode

The electrochemical oxidation of wastewater from DDNP production was investigated using a boron-doped diamond (BDD) thin film electrode. The effects of operating factors such as cell voltage, interelectrode distance and additive NaCl have been studied. This study showed that the chemical oxygen demand (COD) reduction is most influenced by the applied cell voltage. Higher current densities resulting from higher cell voltages increase the formation of oxidative reagents resulting in an increased COD removal rate. The maximum COD removal was 57% after 210 min, with an energy consumption of 14.90 KWh·kg-1COD when cell voltage was 12V, interelectrode distance was 3cm and additive NaCl concentration was 1g·L-1. The use of BDD thin film electrode for the treatment of DDNP production wastewater appears commercially feasible.

Electrochemical Behaviors of Chlorophenol Aqueous Solutions at Boron-Doped Diamond Electrode

The electrochemical behaviors of different chlorophenols at boron-doped diamond thin film electrode were investigated. Four chlorophenols, the 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6- TCP) and pentachlorophenol (PCP), with various number of chlorine atoms in the benzene rings, were studied by using cyclic voltammetry at different scan rates over the potential range of -1 V to 2.5 V (vs MSE). The results indicated that the reactions of the 2-CP, 2,4-DCP and 2,4,6-TCP at the diamond electrode are irreversible and controlled by diffusion, and the irreversible trend increases with the decrease of the chlorine atom number in the benzene ring. However, the activity of the boron-doped diamond film electrode does not depend on the number of the chlorine atom. Different from the three chlorophenols, fouling of the electrode occurs in PCP solutions. The possible electro-oxidation mechanisms are discussed for different chlorophenols.

Anodic oxidation of anthraquinone dye Alizarin Red S at Ti/BDD electrodes

The boron-doped diamond (BDD) thin-film electrode with high quality using industrially titanium plate (Ti/BDD) as substrate has been prepared and firstly used in the oxidation of anthraquinone dye Alizarin Red S (ARS) in wastewaters. The Ti/BDD electrodes are shown to have high concentration of sp 3-bonded carbon and wide electrochemical window. The results of the cyclic voltammetries show that BDD has unique properties such as high anodic stability and the production of active intermediates at the high potential. The oxidation regions of ARS and water are significantly separated at the Ti/BDD electrode, and the peak current increases linearly with increasing ARS concentration. The bulk electrolysis shows that removal of chemical oxygen demand (COD) and color can be completely reached and the electrooxidation of ARS behaves as a mass-transfer-controlled process at the Ti/BDD electrode. It is demonstrated that the performances of the Ti/BDD electrode for anodic oxidation ARS have been significantly improved with respect to the traditional electrodes.

Cyclic Voltammograms of Chlorophenol Oxidation on Boron-Doped Diamond Electrode

The electrochemical behaviors of several chlorophenols were investigated on boron-doped diamond thin film electrode. 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol solutions were prepared as the electrolyte. Such four chlorophenols with various number of chlorine atoms in the benzene ring were studied by cyclic voltammetry at different scan rates between –1V to 2.5V (vs. MSE). The results indicated that the reactions of the 2-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol at the diamond electrode are irreversible and under diffusion control. The irreversible trend increases as the number of the chlorine atoms decreases. However, the activity of the boron-doped diamond film electrode is not affected by the number of the chlorine atom. Different from the three chlorophenols, fouling of the electrode appears in pentachlorophenol solutions.

Preparation of grain size controlled boron-doped diamond thin films and their applications in selective detection of glucose in basic solutions

Boron-doped diamond (BDD) thin films with different crystal grain sizes were prepared by controlling the reacting gas pressure using hot filament chemical vapor deposition (HFCVD). The morphologies and structures of the prepared diamond thin films were characterized by scanning electron microscopy (SEM) and Raman spectroscopy. The electrochemical responses of K4Fe(CN)6 on different BDD electrodes were investigated. The results suggested that electron transfer was faster at the boron-doped nanocrystalline diamond (BDND) thin film electrodes in comparison with that at other BDD thin film electrodes. The prepared BDD thin film electrodes without any modification were used to directly detect glucose in the basic solution. The results showed that the as-prepared BDD thin film electrodes exhibited good selectivity for detecting glucose in the presence of ascorbic acid (AA) and uric acid (UA). The higher sensitivity was observed on the BDND thin film grown on the boron-doped microcrystalline diamond (BDMD) thin film surface, and the linear response range, sensitivity and the low detection limit were 0.25–10 mM, 189.1 μA mmo−1 cm−2 and 25 μM (S/N=3) for glucose in the presence of AA and UA, respectively.

Non-enzymatic glucose detection using as-prepared boron-doped diamond thin-film electrodes

Electrochemical oxidation of glucose in alkaline solution at as-prepared boron-doped microcrystalline diamond (BDMD) and nanocrystalline diamond (BDND) thin-film electrodes is investigated by cyclic voltammetry. The results demonstrate that glucose can be directly oxidized at as-prepared boron-doped diamond (BDD) thin-film electrodes and the curve of the negative scan traces onto the positive scan. The effect of sodium hydroxide concentration on the response of glucose is also studied in the range of 0.02-0.6 M and the optimum concentration of sodium hydroxide is found to be 0.1 M. The voltammetric signal of glucose and the mixture of ascorbic acid (AA) and uric acid (UA) can be observed well-separated at as-prepared BDD thin-film electrodes in 0.1 M sodium hydroxide solution. The peak current is proportional to the glucose concentration in the range 0.25-10 mM with a correlation coefficient of 0.9993 in the presence of AA and UA. Furthermore, the experiment results also show that the non-enzymatic glucose sensor based on as-prepared BDD thin-film electrodes has high sensitivity, good reproducibility and stability.

The structural and electrochemical properties of boron-doped nanocrystalline diamond thin-film electrodes grown from Ar-rich and H 2-rich source gases

The microstructural, electrical and electrochemical properties of boron-doped (ultra)-nanocrystalline diamond (UNCD) films deposited from a CH 4/H 2/Ar source gas mixture were compared with those of boron-doped nanocrystalline diamond (NCD) films grown from a conventional CH 4/H 2 source gas mixture. Scanning electron microscopy, visible-Raman spectroscopy and X-ray diffraction analysis were employed to probe the film morphology and microstructure. Conducting-probe atomic force microscopy (CP-AFM) was used to simultaneously map the morphology and electrical conductivity of the two film types. Spatial heterogeneity in the electrical conductivity was observed for both films as each is composed of regions of high electrical conductivity isolated by more insulating regions. The electrochemical properties were evaluated using the redox couples: Fe(CN) 6 3−/4−, Ru(NH 3) 6 3+/2+, IrCl 6 2−/3−, methyl viologen, dopamine, and Fe 3+/2+. Taken together, the results confirm that even though the morphology and microstructure of UNCD and NCD films are distinct, both boron-doped film types exhibit comparable electrical and electrochemical properties.

A direct electrochemical method for diabetes diagnosis based on as-prepared boron-doped nanocrystalline diamond thin film electrodes

The nonenzymatic glucose sensor based on as-prepared boron-doped nanocrystalline diamond (BDND) thin film electrodes was developed and applied to measure blood glucose. The results show that the relationship between the peak current and the glucose concentration is linear in the range 2.5 × 10 −4−1.2 × 10 −2 M with a correlation coefficient of 0.992 in 0.2 M sodium hydroxide. Different blood samples were measured by the nonenzymatic glucose sensor based on as-prepared BDND thin film electrodes and the blood glucose monitoring system, respectively, and the measurement results obtained from the proposed method were basically similar to those of the commercial glucose device. The relative standard deviation (RSD) of the proposed method was less than 4.41%, and the recovery of blood samples ranged from 95.33% to 105.3%. Additionally, the proposed method has some other advantages such as has high sensitivity, good reproducibility and stability. Therefore the proposed method can be used to measure the blood glucose level with satisfactory results.

The Physicochemical and Electrochemical Properties of 100 and 500 nm Diameter Diamond Powders Coated with Boron-Doped Nanocrystalline Diamond

There is a need for advanced, corrosion-resistant electrocatalyst support materials for use in fuel cells. To this end, electrically conducting diamond powder was prepared by depositing a layer of boron-doped nanocrystalline diamond on 100 and diamond powders. The doped layer was deposited by microwave plasma-assisted chemical vapor deposition using an -rich source gas mixture. After coating, the doped diamond powder had a specific surface area of and an electrical conductivity of . The doped diamond powder had a specific surface area of and an electrical conductivity of after coating. The specific surface area of both powders decreased by ca. 50% after diamond coating due mainly to particle–particle fusion. The electrical measurements provided conclusive evidence for a doped diamond overlayer as the uncoated powders possessed no electrical conductivity. Furthermore, the fact that the electrical properties were unaltered by acid washing confirmed that the conductivity arises from the doped diamond overlayer and not any adventitious carbon impurity on the particle surface, which is removed by such chemical treatment. Scanning electron microscopy images and Raman spectroscopy yielded further evidence in support of a nanocrystalline diamond overlayer. Both powders exhibited electrochemical responses for , , and that were comparable to typical responses seen for high-quality, boron-doped nanocrystalline diamond thin-film electrodes. The electrochemical behavior of the powders was assessed using a pipette electrode that housed the packed powder with no binder. The doped diamond powder electrodes were more plagued by ohmic resistance effects than were the powder electrodes because of reduced particle contact. Importantly, it was found that the doped diamond powder electrodes are dimensionally stable and corrosion-resistant during anodic polarization at vs in at . In contrast, glassy carbon powder polarized under identical conditions underwent significant microstructural degradation and corrosion.

Electrochemical Analysis of Chloramphenicol Using Boron-doped Diamond Electrode Applied to a Flow-Injection System

The electrochemical properties of chloramphenicol at a boron-doped diamond thin-film (BDD) electrode were studied using cyclic voltammetry. The highest current response of chloramphenicol was obtained with phosphate buffer, pH 6 (0.1 M) in 1% ethanol. The relationship between the concentration of chloramphenicol and the current response was linear over the range of 0.1-10 mM (R2=0.9990). The amount of chloramphenicol was analyzed by flow-injection analysis. A thin-layer flow cell equipped with a BDD electrode was used as an amperometric detector, and experiments were carried out at -0.7 V (vs. Ag/AgCl). The linear relationship between the current response and the concentration of chloramphenicol in the range of 0.1-50 microM (R2=0.9948) and the limit of detection of 0.03 microM (S/N=3) were obtained. This method has been successfully applied to the determination of chloramphenicol in sterile eye drops and milk sample by the standard addition method. The average recoveries of chloramphenicol in eye drops were 98.0%, and the average recoveries of chloramphenicol from spiked milk were 93.9-103%.

Voltammetric Determination of 3‐Nitrofluoranthene and 3‐Aminofluoranthene at Boron Doped Diamond Thin‐Film Electrode

AbstractThe voltammetric behavior of 3‐nitrofluoranthene and 3‐aminofluoranthene was investigated in mixed methanol‐water solutions by differential pulse voltammetry (DPV) at boron doped diamond thin‐film electrode (BDDE). Optimum conditions have been found for determination of 3‐nitrofluoranthene in the concentration range of 2×10−8–1×10−6 mol L−1, and for determination 3‐aminofluorathnene in the concentration range of 2×10−7–1×10−5 mol L−1, respectively. Limits of determination were 3×10−8 mol L−1 (3‐nitrofluoranthene) and 2×10−7 mol L−1 (3‐aminofluoranthene).

Total inorganic arsenic detection in real water samples using anodic stripping voltammetry and a gold-coated diamond thin-film electrode

An accurate method for total inorganic arsenic determination in real water samples was developed using differential pulse anodic stripping voltammetry (DPASV) and a Au-coated boron-doped diamond thin-film electrode. Keys to the method are the use of a conducting diamond platform and solid phase extraction for sample preparation. In the method, the As(III) present in the sample is first detected by DPASV. The As(V) present is then reduced to As(III) by reaction with Na 2SO 3 and this is followed by a second detection of As(III) by DPASV. Interfering metal ions (e.g., Cu(II)) that cause decreased electrode response sensitivity for arsenic in real samples are removed by solid phase extraction as part of the sample preparation. For example, Cu(II) caused a 30% decrease in the As stripping peak current at a solution concentration ratio of 3:1 (Cu(II)/As(III)). This loss was mitigated by passage of the solution through a Chelex 100 cation exchange resin. After passage, only a 5% As stripping current response loss was seen. The effect of organic matter on the Au-coated diamond electrode response for As(III) was also evaluated. Humic acid at a 5 ppm concentration caused only a 9% decrease in the As stripping peak charge for Au-coated diamond. By comparison, a 50% response decrease was observed for Au foil. Clearly, the chemical properties of the diamond surface in the vicinity of the metal deposits inhibit molecular adsorption on at least some of the Au surface. The method provided reproducible and accurate results for total inorganic arsenic in two contaminated water samples provided by the U.S. Bureau of Reclamation. The total inorganic As concentration in the two samples, quantified by the standard addition method, was 23.2 ± 2.9 ppb for UV plant influent water and 16.4 ± 0.9 ppb for Well 119 water ( n = 4). These values differed from the specified concentrations by less than 4%.