Porous Boron-doped Diamond Electrode Research Articles

Construction of porous diamond film with enhanced electric double-layer capacitance via regrowth of diamond nanoplatelets

The engineering of porous boron-doped diamond (BDD) film has sparked significant interest in improving electric double-layer (EDL) capacitance. However, the presence of disordered and tortuous pores in the BDD film hinders the accessibility of the bottom pore surface area, leading to a decrease in specific EDL capacitance. Herein, a novel porous BDD film with vertically open pore channels is constructed through the overcoating of diamond nanoplatelet template with a BDD layer using chemical vapor deposition. Electrochemical investigations manifest that the specific areal EDL capacitance of the porous BDD is ∼428 times greater than that of the planar BDD film. More impressively, the porous BDD film demonstrates a higher specific volumetric EDL capacitance (39.30 F/cm3) and superior long-term stability (100% capacitance retention after 12,000 cycles), surpassing the performance of most developed porous BDD electrodes. The exceptional performance of the porous BDD film was attributed to the abundant vertically open pore channels, good hydrophilic property, maximized electrochemical available area, and good chemical/mechanical stability. This work benefits the development of the BDD film as an EDL micro-capacitor electrode, and the methodology proposed here shows great potentials to fabricate an ordered porous BDD nanostructure with large specific area for more electrochemical applications.

Efficient electrochemical degradation of X-GN dye wastewater using porous boron-doped diamond electrode

Surface porous Ti substrates were obtained by electrodeposition–hot melt–alkali etching. Porous-Ti/BDD and flat-Ti/BDD electrodes were prepared for comparative study. The results of SEM, Raman, and XRD analyses show that the BDD films of these two electrodes had good uniformity and stable quality. The electrochemical window (EW) and electrochemical-active surface area (EASA) of the porous-Ti/BDD electrode is as high as 4.21 V and 22.78 cm2 (11.39 cm2/cm2), respectively. Furthermore, the electrochemical catalytic performance and degradation mechanism of porous-Ti/BDD electrode as the anode were studied by the electrolysis of Active Orange dye X-GN (X-GN), and the optimal electrochemical degradation operating parameters were obtained. The results show that when the degradation time was 50 min, the X-GN was completely decolorized. The TOC removal rate reached 69.24%, and the energy consumption was 5.62 kWh m−3. The contribution rate of •OH and SO4•− was calculated to be 91.40% and 1.26% by radical quenching experiments, respectively, indicating that the active substances in the degradation system were mainly •OH and SO4•−. The high specific surface characteristics of porous-Ti/BDD electrode enhanced its electrochemical oxidation advantages, and it showed a high degradation efficiency and low energy consumption for the treatment of X-GN simulated wastewater.

Multifunctional and Mechanically Robust Porous Diamond with Large Electroactive Surfaces via Electrically Conductive and Insulating Templates for 3D Electrode Applications

AbstractHighly functional 3D biological systems, which are ordinary in this physical world, suggest that traditional planar/flat materials when assembled into 3D variants, can deliver significantly higher levels of functionality and efficiency. Thanks to its set of unique properties, diamond has received significant recognition as the material of choice for a variety of functional platforms, however, implementation of diamond in real‐world applications has lagged behind alternative materials, which offer a greater degree of versatility. In this regard, for applications to benefit from diamond‐specific properties, approaches on fabrication of diamond beyond the common planar form in a practical and scalable manner are required today. Capitalizing on the ability to synthesize diamond over large areas, this study demonstrates fabrication of porous boron‐doped diamond (BDD) in freestanding form and on wafer‐compatible sizes. Porous BDD electrodes deliver robust electrochemical stability and exceptional electrical characteristics. Aiming to utilize the full potential of diamond properties, this study examines the impact of the BDD porous structure on the ability of electrodes to effectively remove organic pollutants from simulated wastewater and to provide enhanced sensitivity/selectivity of biologically active compounds. This study represents an important step in achieving diamond with extended functionality suitable for industrial/commercial scale implementation.

Porous boron-doped diamond for efficient electrocatalytic elimination of azo dye Orange G

Boron-doped diamond (BDD) is an ideal material being used for electrocatalytic elimination of environmental organic pollutants, but the commercial BDD electrodes have several limitations such as small electroactive area, slow mass transfer and low pollutants decomposition efficiency. In this paper, porous BDD electrodes with different pore sizes were synthesized by replicating porous Ti (powder metallurgy) with three-dimensional interoperable network structure, controllable aperture and porosity in a hot filament chemical vapor deposition (HFCVD) system. Various aspects of porous BDD with different pore sizes in terms of physicochemical properties, electrocatalytic reaction kinetics and mass transfer, which had not been previously researched, were systematically discussed. Meanwhile, some fundamental issues such as the enhancement mechanism of reaction kinetics of porous electrodes, the electrocatalytic degradation mechanism and pathways of contaminants on flat and porous BDD electrodes have been thoroughly investigated. Porous BDD electrodes had significantly higher Orange G (OG) electrocatalytic apparent reaction rate constants (up to 5.55 times that with flat BDD) and dramatically lower electrical energy per order (down to 25% that with flat BDD) for pollutant removal due to their increased electroactive area, reduced charge transfer resistance, and enhanced mass transfer. The electroanalysis, hydroxyl radical quenching and intermediates identification revealed the electrocatalytic degradation mechanism and reaction pathways of OG. In general, Porous BDD electrodes combined the properties of BDD and porous Ti, making them a commercially applicable and efficient material with high electroactive area, high electrocatalytic activity, long-term stability and low cost for electrocatalytic elimination of environmental organic pollutants.

Enhancing electroanalytical performance of porous boron-doped diamond electrodes by increasing thickness for dopamine detection

Novel porous boron-doped diamond (BDDporous)-based materials have attracted lots of research interest due to their enhanced detection ability and biocompatibility, favouring them for use in neuroscience. This study reports on morphological, spectral, and electrochemical characterisation of three BDDporous electrodes of different thickness given by a number of deposited layers (2, 3 and 5). These were prepared using microwave plasma-enhanced chemical vapour deposition on SiO2 nanofiber-based scaffolds. Further, the effect of number of layers and poly-l-lysine coating, commonly employed in neuron cultivation experiments, on sensing properties of the neurotransmitter dopamine in a pH 7.4 phosphate buffer media was investigated. The boron doping level of ∼2 × 1021 atoms cm−3 and increased content of non-diamond (sp2) carbon in electrodes with more layers was evaluated by Raman spectroscopy. Cyclic voltammetric experiments revealed reduced working potential windows (from 2.4 V to 2.2 V), higher double-layer capacitance values (from 405 μF cm−2 to 1060 μF cm−2), enhanced rates of electron transfer kinetics and larger effective surface areas (from 5.04 mm2 to 7.72 mm2), when the number of porous layers increases. For dopamine, a significant boost in analytical performance was recognized with increasing number of layers using square-wave voltammetry: the highest sensitivity of 574.1 μA μmol−1 L was achieved on a BDDporous electrode with five layers and dropped to 35.9 μA μmol−1 L when the number of layers decreased to two. Consequently, the lowest detection limit of 0.20 μmol L−1 was obtained on a BDDporous electrode with five layers. Moreover, on porous electrodes, enhanced selectivity for dopamine detection in the presence of ascorbic acid and uric acid was demonstrated. The application of poly-l-lysine coating on porous electrode surface resulted in a decrease in dopamine peak currents by 17% and 60% for modification times of 1 h and 15 h, respectively. Hence, both examined parameters, the number of deposited porous layers and the presence of poly-l-lysine coating, were proved to considerably affect the characteristics and performance of BDDporous electrodes.

Achieving high capacitance from porous boron-doped diamond by tuning the surface termination

Porous boron-doped diamond (PBDD) electrode with a high potential window, excellent stability, controllable conductivity, enhanced specific area, and tunable surface termination is a promising electrode material for the candidate. The surface termination of the PBDD electrode is easily tuned by the cyclic voltammetry (CV) scanning process with a positive potential, and an oxygen-terminated (OT) surface is achieved. The OT PBDD electrode exhibits a peak specific capacitance of 20.31 mF cm −2 (38.3% increase compared with the HT PBDD electrode, at 100 mV s −1 ) when 2.4 V (vs. Ag/AgCl) potential is applied, and it further comes to 36.74 mF cm −2 (81.8% increase than the HT PBDD electrode, at 10 mV s −1 ) with a 2.7 V (vs. Ag/AgCl) polarization potential. As the polarization voltage further increases to 3.0 V (vs. Ag/AgCl) or higher, the specific capacitance decrease. The OT PBDD electrode also keeps capacitance retention of 94.8% after 6000 CV cycles at 200 mV s −1 . Moreover, we built up a symmetric device using the OT PBDD as the electrode, which exhibits good electrochemical performance, such as wide potential, high energy density (15.1 Wh kg −1 ), and high power density (4.05 kW kg −1 ). • The PBDD is synthesized via regrowth of diamond nanoparticles in an Ar atmosphere. • The PBDD electrode achieves an oxygen-terminated (OT) surface by anodic polarization. • The OT PBDD device's energy density increases from 7.37 to 15.1 Wh kg −1 after polarization. • The OT PBDD device has the same potential window as the hydrogen-terminated PBDD.

A novel modification to boron-doped diamond electrode for enhanced, selective detection of dopamine in human serum

In this work, we proposed a novel modification technique to immobilize nanoparticles by the nanopores on a boron-doped diamond surface, preventing the aggregation of nanoparticles physically and improving the stability of nanoparticles layer by the anchoring effect. All the exposed surfaces of a bare boron-doped diamond were etched into nanoporous form and larger electrochemically active surface area was obtained on the porous boron-doped diamond electrode. The carbon black nanoparticles modified porous boron-doped diamond electrode showed good selectivity to separate the oxidation potential of three molecules, but led to an extra increase in the peak current of dopamine (DA). The carbon black/Nafion modified porous diamond electrode effectively suppress the oxidation current of ascorbic acid (AA), enhancing the sensitivity of DA. The dual layer treatment enables a wide linear range, 0.1–100 μM and a low limit of detection, 54 nM for DA detection, which is almost unaffected by the excess AA and uric acid (UA). At last, real sample tests of the carbon black/Nafion modified porous diamond electrode was validated by applying to the detection of DA in human serum and dopamine hydrochloride injection, which were found to be promising at our preliminary experiments. Additionally, the fabricated carbon black/Nafion modified porous diamond electrode also demonstrated good stability and long-term functionality.

Hybrid supercapacitors from porous boron-doped diamond with water-soluble redox electrolyte

Hybrid supercapacitors (HSCs) can simultaneously achieve battery-level energy as well as capacitor-level power and cycle life in a single device. To construct such HSCs, porous boron-doped diamond (BDD) films fabricated by a template-free method via regrowth of diamond nanoparticles were employed as the electrodes and water-soluble redox couples (Fe (CN)63−/4−) as the electrolyte. For the three-electrode system, the porous BDD electrode delivers a capacitance of 13.08 mF cm−2 in 1.0 M Na2SO4, and a capacity of 78.23 mAh g−1 in 0.05 M Fe (CN)63−/4− + 1.0 M Na2SO4 when a scan rate of 10 mV s−1 is applied. For the symmetric two-electrode system, the porous BDD electrode exhibits a capacitance of 13.04 mF cm−2 in 1.0 M Na2SO4 and a capacity of 34.74 mAh g−1 in 0.05 M Fe (CN)63−/4− + 1.0 M Na2SO4 at the same scan rate. The capacitance (capacity) remains about 92% of its initial value after 5000 cyclic voltammetry cycles in all conditions. The specific power densities (normalized by the mass of electrode active material only) are 0.17 and 1.05 kW kg−1, with their specific energy densities of 5.51 and 38.10 W h kg−1, respectively. Thus, the porous BDD films, together with the water-soluble redox electrolyte, have profound applications in high-performance hybrid supercapacitors construction for future power devices.

Electrochemical detection of clenbuterol with gold-nanoparticles-modified porous boron-doped diamond electrode

In this work, an electrochemical electrode material consisting of porous boron-doped diamond (pBDD) films modified with gold nanoparticles (Au-NPs), named as Au-pBDD, has been fabricated by a wet annealing process of water vapor on a BDD film surface with a sputtered Au nanolayer. Experimentally, the electrochemical sensor with the Au-pBDD electrode exhibits high sensitivity to clenbuterol (CLB) with a low detection limit of 0.066 µM and a wide linear detection range of 0.1 µM–100 µM. The high performance sensitivity can be attributed to the designed electrode having increased surface area with porous structure and reduced impedance by depositing Au nanoparticle, leading to the effective improvement of the electrochemical activity. The reproducibility, stability, repeatability, and anti-interference for the electrodes, which are required in practical applications, have been examined showing higher performances with respect to the most traditional electrodes for trace CLB detection.

High-performance 2.6 V aqueous symmetric supercapacitor based on porous boron-doped diamond via regrowth of diamond nanoparticles

Having a wider potential window and higher stability than other traditional sp2-based carbon electrodes, heavily boron-doped diamond (BDD) electrode with three-dimensional porous nanostructure can considerably enhance the specific capacitance, making it one of the most promising electrode materials. In the work, we present a simple and reproducible method to create such a porous BDD film by using self-assembly seeding approach and microwave plasma chemical vapor deposition (MPCVD). The fabricated porous BDD electrode exhibits an enhanced capacitance of 17.18 mF cm−2, and an outstanding stability of about 95% charge retention after 10000 cycles in aqueous solution in three-electrode system. Moreover, the specific capacitance can be further enhanced by producing multilayer films. By using porous BDD as electrodes, a 2.6 V aqueous symmetric supercapacitor with specific capacitance of 25.48 mF cm−2 is obtained. The capacitance retention is about 91.5% after 10000 CV cycles. The energy and power densities of the device are about 5.46 Wh kg−1 and 2.9 kW kg−1, respectively. The fabrication of this porous BDD film with high capacitance and high stability is free of template, binder, as well as etching process, which may have potential impact on many applications for future energy storage devices.

Porous boron doped diamond for dopamine sensing: Effect of boron doping level on morphology and electrochemical performance

Complex characterization of as-deposited conventional planar and newly available porous boron doped diamond (BDD) films with various boron doping levels (B/C ratio in the gas phase: 500 ppm, 1000 ppm, 2000 ppm, 4000 ppm, and 8000 ppm) was carried out by scanning electron microscopy, Raman spectroscopy and electrochemistry by performing cyclic voltammetric (CV) experiments with outer- and inner-sphere redox probes [Ru(NH3)6]3+/2+, [Fe(CN)6]3−/4−, and dopamine. The double layer capacitance was estimated from CV and electrochemical impedance spectroscopic measurements. For planar BDD films, a roughly 80% increase in the double layer capacitance, a 100 mV narrower potential window and a 51 mV negative shift of the peak potential of dopamine were observed when the boron doping level increased from 500 ppm to 8000 ppm. Conversely, higher sp2 carbon content confirmed by Raman spectra affects the electrochemical performance of porous samples more significantly than the doping level. For the set of porous BDD electrodes, the double layer capacitance decreased by ca 95% with increasing boron content, peak-to-peak separation values of the studied inorganic redox markers were lower than 59 mV, suggesting their partial adsorption in the bulk of the material, and lower potentials for dopamine oxidation approaching values obtained for other sp2 carbon-based materials were recorded, but no dependency of potential values on boron concentration was revealed. Enhanced electron transfer rate on porous BDD materials resulted in increased sensitivity for dopamine detection using square-wave voltammetry in contrast to the planar set of electrodes. The lowest detection limit of 2 × 10−7 mol L−1 was estimated in a medium of 0.1 mol L−1 phosphate buffer pH 7.4 on B/C 4000 ppm porous electrodes with increased BDD growth time, without any activation applied between the individual scans. Moreover, for selected porous electrodes, improved selectivity for dopamine sensing in excess of common interfering compounds such as uric acid, ascorbic acid and paracetamol was achieved.

Diamond/Porous Titanium Nitride Electrodes With Superior Electrochemical Performance for Neural Interfacing.

Robust devices for chronic neural stimulation demand electrode materials which exhibit high charge injection (Qinj) capacity and long-term stability. Boron-doped diamond (BDD) electrodes have shown promise for neural stimulation applications, but their practical applications remain limited due to the poor charge transfer capability of diamond. In this work, we present an attractive approach to produce BDD electrodes with exceptionally high surface area using porous titanium nitride (TiN) as interlayer template. The TiN deposition parameters were systematically varied to fabricate a range of porous electrodes, which were subsequently coated by a BDD thin-film. The electrodes were investigated by surface analysis methods and electrochemical techniques before and after BDD deposition. Cyclic voltammetry (CV) measurements showed a wide potential window in saline solution (between −1.3 and 1.2 V vs. Ag/AgCl). Electrodes with the highest thickness and porosity exhibited the lowest impedance magnitude and a charge storage capacity (CSC) of 253 mC/cm2, which largely exceeds the values previously reported for porous BDD electrodes. Electrodes with relatively thinner and less porous coatings displayed the highest pulsing capacitances (Cpulse), which would be more favorable for stimulation applications. Although BDD/TiN electrodes displayed a higher impedance magnitude and a lower Cpulse as compared to the bare TiN electrodes, the wider potential window likely allows for higher Qinj without reaching unsafe potentials. The remarkable reduction in the impedance and improvement in the charge transfer capacity, together with the known properties of BDD films, makes this type of coating as an ideal candidate for development of reliable devices for chronic neural interfacing.

Electrochemical characterization of porous boron-doped diamond prepared using SiO2 fiber template

Porous boron-doped diamond (BDD) is fabricated by consecutive plasma enhanced chemical vapor deposition on a 3D porous SiO2 fiber template deposited by spin coating (SC). The fabricated highly doped and mechanically stable porous BDD layers are characterized by scanning electron microscopy (SEM) and Raman spectroscopy. The roughness factor of the prepared porous BDD, depending on the number of porous layers, was determined from cyclic voltammetry (RFCV) and from krypton adsorption isotherms – BET, (RFBET). Differences in determination of the roughness factor using these two methods are discussed. Electrochemical measurements (cyclic voltammetry and galvanostatic charge/discharge cycling) of porous BDD are performed in aqueous electrolyte solutions with different composition and pH values. The highest electric double-layer capacitance of ca. 2 mF·cm−2, related to the projected geometric (2D) surface area, is obtained for the thickest (26 μm) porous BDD electrode measured in 0.5 M H2SO4 electrolyte solution. The capacitance of the same porous BDD normalized to the total physical surface area (3D) determined by BET is 45 μF·cm−2. The electrocatalytic activity of porous BDD electrodes is studied using a hexaammineruthenium(III/II) redox probe, and the electrochemical cycle stability is determined by galvanostatic charge/discharge. The charge retention of the thickest porous BDD samples after removal of non-diamond impurities by an oxidative treatment is ca. 77% after 3000 cycles.

Porous boron-doped diamond electrode for detection of dopamine and pyridoxine in human serum

A porous boron-doped diamond (PBDD)/Ta sensing electrode was prepared for the fast, sensitive, stable, and discriminative detection of dopamine (DA) and pyridoxine (vitamin B6) in human serum. All the exposed surfaces of the diamond grains of the BDD layer were etched into a porous form, with pore sizes of less than 500 nm and an average depth of about 200 nm. The electrochemical performance characteristics of the PBDD layer and the reaction mechanisms enabling the detection of DA and vitamin B6 were studied. Large numbers of oxygen-containing groups on the PBDD surface, as well as the activity difference of the different planes, enabled us to successfully distinguish between DA and B6 by using the PBDD/Ta electrode. The low background current of PBDD, the large active area of the porous surface, and the high electron transfer properties led to the PBDD electrode having a high sensitivity. Therefore, this sensor can be used to stably detect DA and B6 in serum. Aberrant levels of DA and vitamin B6 in body fluids are key risk indicators for some diseases; thus, monitoring the levels of both and other species in serum is of great significance to clinical diagnoses.

Application of porous boron-doped diamond electrode towards electrochemical mineralization of triphenylmethane dye

The aim of this study is to investigate the electrochemical degradation and decolorization of triphenylmethane dyexylenol orange (XO) on boron-doped diamond (BDD) electrodes. A series of parameters, including electrode materials, current density, initial dye concentration and electrolyte composition, are examined to discuss the effect of these factors in terms of chemical oxygen demand (COD) removal, current efficiency and decolorization rate. Complete decolorization and mineralization of XO could be realized on BDD electrodes while the oxidation is mass transfer controlled, and the degradation progress performs better performance in case of porous BDD electrode comparing with flat BDD electrode. The enhancement of effectiveness is highly correlated to the structure of electrode material, where porous BDD film provides more active sites for hydroxyl radicals. The presence of Cl− in the solution promotes the COD and color removal due to the formation of active chlorine. Porous Ti/BDD electrode presents the excellent potential in electrochemical decolorization and mineralization of triphenylmethane dye.

Fabrication of porous boron-doped diamond electrodes by catalytic etching under hydrogen–argon plasma

Porous boron-doped diamond (BDD) was prepared by hydrogen–argon plasma etching using electrodeposited Ni nanoparticles as a catalyst. The etching process and formation mechanism of porous BDD were investigated by changing the etching time from 30s to 300s. Pores were produced due to the C atoms around Ni nanoparticles are easy to react with hydrogen plasma and form methane. With the increase of etching time, the pore size increased, the pore density decreased, and the pore depth first increased and then maintained unchanged. The sp2-bonded graphitic carbons existing on the surface of BDD increase with increasing etching time due to the increase of surface area. No preferential etching was observed due to the high energy of argon plasma. The electrochemical behaviors of the pristine and porous BDD electrodes were characterized by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS). The results showed that the porous BDD electrode exhibited high specific capacitance, which is attributed to its high electrical conductivity and large specific surface area. The highest specific capacitance of porous BDD electrode is 9.55mFcm−2, which is 22 times higher than that of pristine BDD electrode. The specific capacitance retention of the porous BDD electrode reduced to 98.2% of the initial capacitance after 500 cycles and then increased to 120.0% after 10,000 cycles. For the first 500 cycles, the reduction of capacitance can be attributed to the dissolution of Ni nanoparticles that attached on the porous BDD surface or buried in the shallow layer. The capacitance increase after 10,000 cycles is due to the better contact of the electrolytic solution with the residual Ni with the increase of cycle number.

Anodic oxidation of aspirin on PbO 2 , BDD and porous Ti/BDD electrodes: Mechanism, kinetics and utilization rate

Abstract The electrochemical abatement of aspirin, a representative anti-inflammatory drug, is carried out through anodic oxidation by employing PbO 2 , boron-doped diamond (BDD) and porous Ti/BDD as anodes. The effect of nature characteristic and structure of the electrode material on the electrochemical oxidation is systematic investigated. The redox behavior of aspirin on different electrodes is studied by linear sweep voltammetry. Completely mineralization of aspirin could be achieved on BDD electrodes. The results show that the electrochemical incineration of aspirin on three electrodes follows a pseudo first-order kinetics behavior with apparent rate constant of 0.051, 0.185 and 0.367 h −1 for PbO 2 , flat BDD and porous BDD electrode. Electrochemical degradation mechanism on BDD electrodes involves the direct and indirect electrochemical oxidation while there is only indirect oxidation for aspirin on PbO 2 electrode. Porous Ti/BDD presents the best excellent electrochemical oxidation ability for aspirin compared with flat BDD and PbO 2 electrode. The discrepancy of electrochemical oxidation could be explained in terms of in situ generation and utilization rate of hydroxyl radicals on the surface of electrode materials.

Improved electrochemical performance of boron-doped diamond electrode depending on the structure of titanium substrate

Abstract This work is focused on the role of porous titanium (Ti) substrate on the electrochemical performance of boron-doped diamond (BDD) films. BDD film deposited on porous Ti substrate combines the excellent property of porous Ti and BDD film, porous Ti endows the film three-dimensional (3D) porous performance and enhances the surface area of BDD electrode. The effective electrochemical surface area of 3D-Ti/BDD electrode is 8.37 cm 2 cm − 2 , 3.2 times as much as that of conventional plate BDD electrode while smaller electron transfer resistance (31.3 Ω cm 2 ) for Fe(CN) 6 3 − /Fe(CN) 6 4 − redox couple on 3D-Ti/BDD electrode is obtained compared to 128.3 Ω cm 2 . 3D-Ti/BDD electrode presents higher response current and the degradation of aspirin reveals that corresponding kinetic constant for plate and 3D-Ti/BDD electrode is 0.185 h − 1 and 0.367 h − 1 , respectively. Moreover, porous BDD electrode owns higher stability analyzing by accelerated life tests, 25% higher than plate BDD electrode. The enhancement of electrocatalytic activity and stability is essentially attributed to porous structure of Ti substrate.

Enhanced electrochemical oxidation of organic pollutants by boron-doped diamond based on porous titanium

The main aim of the present study was to explore the potential of boron-doped diamond (BDD) film electrode on porous titanium (Ti) substrate to promote the electrochemical oxidation of organic pollutants. Porous Ti endowed the Ti/BDD film three-dimensional porous structure. The electrochemical effective surface area for porous Ti/BDD anode was 8.37cm2/cm2, 3.2 times as much as that of two-dimensional flat Ti/BDD electrode. Furthermore, the generation ability and rate of hydroxyl radical (OH) on porous BDD electrode were enhanced due to the porous structure of BDD film. The step currents on porous Ti/BDD were about 2 times of those on flat Ti/BDD electrode from chronoamperometry curves, porous Ti/BDD exhibited superior indirect electrochemical oxidation ability. The results of electrodegradation of several typical organic pollutants (oxalic acid, phenol, sodium dodecylbenzene sulfonate, xylenol orange) revealed that current efficiencies on porous Ti/BDD electrode were about 30% higher compared with flat BDD electrode, corroborating the enhanced of electrochemical oxidation as the introduction of porous Ti substrate. Moreover, the discrepancy between promotion of COD removal rate and enhancement of OH was discussed.

Porous boron-doped diamond electrodes fabricated via two-step thermal treatment

A two-step thermal treatment method was developed for the fabrication of porous conductive boron-doped diamond (BDD) electrodes. The first step involved graphitization of the BDD thin film surface to form a fine microstructure by heating in an argon atmosphere at 1000°C. The second step was removal of the graphitic components by oxidation in air at 425°C. The heat treatment resulted in the formation of dense pores with several tens to several hundred nanometer sizes or smaller on the BDD surface. The pore formation mechanism was discussed by microscopic observation of the (111) and (100) crystal facets on the treated BDD surface. The porous BDD electrode exhibited a double-layer capacitance (Cdl) of ca. 140μFcm−2, which was estimated from cyclic voltammetry (CV) and galvanostatic measurements in an aqueous electrolyte. This Cdl value was approximately 40 times larger than that for the as-deposited BDD electrode, while the potential window remained wide at ca. 3V.