Fabrication of a boron-doped nanocrystalline diamond grown on an WC–Co electrode for degradation of phenol
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2022-01-01 |
| Journal | RSC Advances |
| Authors | Tao Zhang, Zhe Xue, Ying Xie, Guodong Huang, Guangpan Peng |
| Institutions | Wuxi Institute of Technology, Shanghai Ocean University |
| Citations | 11 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This research focuses on fabricating highly stable and efficient Boron-Doped Nanocrystalline Diamond (BDD) electrodes on a novel Cemented Carbide (WC-Co) substrate for electrochemical oxidation.
- Novel Substrate: WC-Co was successfully used as the substrate via Hot Filament Chemical Vapor Deposition (HFCVD), offering superior adhesion and lower thermal expansion mismatch compared to conventional Si, Ti, or Nb substrates.
- Material Quality: The resulting nanocrystalline BDD films (4 µm thick, 100 nm grain size) were highly uniform, pinhole-free, and exhibited low compressive stress (-2.3 GPa).
- Electrochemical Performance: The WC-Co/BDD electrode demonstrated a wide electrochemical window of 3.8 V and extremely low background currents in 0.5 mol L-1 H2SO4.
- Stability Achievement: The electrode showed excellent electrochemical stability, achieving a service life exceeding 400 hours in an Accelerated Life Test (ALT) at a high current density (1 A cm-2).
- Pollutant Degradation: The electrode exhibited high activity in degrading high-concentration phenol (25 mmol L-1), reducing the Chemical Oxygen Demand (COD) from 5795 mg L-1 to 85 mg L-1.
- Efficiency: The mineralization process achieved an average instantaneous current efficiency (ICE) of approximately 46%.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Substrate Material | WC-Co (6% Co) | N/A | Used for enhanced adhesion |
| Film Type | Nanocrystalline BDD | N/A | Deposited via HFCVD |
| Film Thickness | 4 | µm | After 270 min growth |
| Grain Size | ~100 | nm | Highly uniform morphology |
| Residual Stress (Calculated) | -2.3 | GPa | Compressive stress (Raman shift) |
| Boron Concentration ([B]/[C]gas) | 5000 | ppm | Atomic ratio in gas phase |
| Boron Concentration (Raman Est.) | 3.5 x 1021 | cm-3 | Estimated via 500 cm-1 band |
| Resistivity (WC-Co/BDD) | 0.2 | mΩ cm | High electrical conductivity |
| Electrochemical Window | 3.8 | V | In 0.5 mol L-1 H2SO4 |
| ALT Service Life | >400 | hours | @ 1 A cm-2 in 3 mol L-1 H2SO4 |
| Initial Phenol Concentration | 25 | mmol L-1 | High concentration test |
| Initial COD | 5795 | mg L-1 | Phenol solution |
| Final COD | 85 | mg L-1 | After 43 Ah L-1 charge loading |
| Average Current Efficiency (ICE) | ~46 | % | For phenol mineralization |
| Phenol Oxidation Potential | ~1.5 | V | Lower than water decomposition potential |
| Redox Behavior (K3[Fe(CN)6]) | Quasi-reversible | N/A | Ip,a/Ip,c ratio close to 1 |
Key Methodologies
Section titled “Key Methodologies”The nanocrystalline BDD films were fabricated using a self-made Hot Filament Chemical Vapor Deposition (HFCVD) system.
- Substrate Preparation (WC-Co):
- WC-Co rods (3 mm diameter, 6% Co) were chemically pretreated using Murakami’s reagent (30 min) and Caro’s acid (60 s) to remove cobalt binder from the surface.
- Substrates were subsequently abraded using 5 µm commercial diamond powders to increase surface defects and enhance diamond nucleation density.
- HFCVD Setup:
- Tantalum wires (Φ 0.5 mm) were used as hot filaments.
- The system employed a dynamic boron-doping method.
- Nucleation and Growth Parameters (Table 1):
| Parameter | Nucleation Phase | Growth Phase |
|---|---|---|
| CH4/H2 Ratio | 2.0% | 1.5% |
| [B]/[C]gas Ratio | 5000 ppm | 5000 ppm |
| Pressure | 2 kPa | 2 kPa |
| Substrate Temperature | 800 °C | 850 °C |
| Filament Temperature | 2000 ± 200 °C | 2200 ± 200 °C |
| Duration | 30 min | 270 min |
- Electrochemical Testing:
- Potential Window/CV: Tested in a three-electrode cell using 0.5 mol L-1 H2SO4 electrolyte.
- Accelerated Life Test (ALT): Conducted in 3 mol L-1 H2SO4 at a constant current density of 1 A cm-2.
- Pollutant Degradation: Phenol (25 mmol L-1) was degraded using a constant current density of 100 mA cm-2. COD was measured using a visible spectrophotometer.
Commercial Applications
Section titled “Commercial Applications”The WC-Co/BDD electrode technology is highly relevant to industries requiring robust, long-life, and highly efficient electrochemical anodes.
- Wastewater Treatment (Primary Application):
- Refractory Organics: Effective mineralization of highly hazardous, non-biodegradable pollutants found in chemical, pharmaceutical, pesticide, and printing/dyeing effluents (e.g., phenol, aniline, dyes).
- High Load Processing: Demonstrated capacity to handle high pollutant concentrations (25 mmol L-1 phenol) efficiently.
- Industrial Electrochemistry:
- Harsh Environments: Suitable for processes requiring high anodic stability and resistance to corrosion, particularly in strong acidic media (proven stability in 3 mol L-1 H2SO4).
- Electrosynthesis: The wide potential window and low background current are ideal for selective oxidation reactions in organic synthesis.
- Protective Coatings:
- Tooling: WC-Co is a common material for cutting tools. The BDD coating provides extreme hardness and chemical inertness, extending tool life in aggressive machining or chemical environments.
- Electrochemical Sensing:
- The low background current and stable surface properties inherent to BDD make it an excellent platform for sensitive detection of trace organic and inorganic species.
View Original Abstract
WC-Co is applied as the substrate instead of conventional ones, on which nanocrystalline BDD films are deposited by HFCVD. WC-Co/BDD electrode like the standard BDD shows a wide potential window and a good mineralization capacity in phenol.