Influence of temperature on the electrochemical window of boron doped diamond - a comparison of commercially available electrodes
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-09-24 |
| Journal | Scientific Reports |
| Authors | Maeve McLaughlin, Emma Dunlop, Alexander C. PakpourâTabrizi, DĂ©bora C. Faria, Richard B. Jackman |
| Institutions | London Centre for Nanotechnology, Schlumberger (United Kingdom) |
| Citations | 18 |
| Analysis | Full AI Review Included |
Influence of Temperature on Boron Doped Diamond Electrochemical Windows: A 6CCVD Technical Analysis
Section titled âInfluence of Temperature on Boron Doped Diamond Electrochemical Windows: A 6CCVD Technical AnalysisâExecutive Summary
Section titled âExecutive SummaryâThis research provides critical data on the performance and stability of Boron Doped Diamond (BDD) electrodes in high-temperature electrochemical environments, directly informing material selection for extreme applications (e.g., oil well sensing).
- Material Focus: Heavily Boron Doped Polycrystalline Diamond (PCD-BDD) with doping concentrations exceeding 1020 atoms/cmÂł.
- Temperature Stability: The electrochemical window (ECW) of all BDD electrodes tested consistently narrows as temperature increases from 21 °C to 125 °C, confirming thermal activation of redox reactions.
- Surface Quality Impact: Unpolished BDD (RA ~ 50 ”m) exhibited the widest ECW and higher activation energies compared to polished BDD (RA ~ 50 nm). This is attributed to the lower proportion of spÂČ carbon content on the rougher, unpolished surface.
- Termination vs. Roughness: The study determined that surface roughness (and resulting spÂČ/spÂł carbon ratio) has a significantly greater impact on the ECW than the surface termination (Hydrogen vs. Oxygen).
- Methodology Standard: The linear fit method for ECW determination is validated as a more reliable standard for cross-literature comparison, as it is less sensitive to mass transport effects than the arbitrary Jcut-off method.
- Application Relevance: BDD electrodes remain suitable for high-temperature analysis, offering versatility for detecting redox peaks within the narrowed window range.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental results, focusing on material properties and performance metrics.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Boron Doping Concentration | > 1020 | atoms/cmÂł | Heavily Doped BDD (Electrochemical Grade) |
| Initial Substrate Dimensions | 10 x 10 x 0.5 | mm | Purchased material |
| Working Electrode Diameter | 3 | mm | Laser cut for testing |
| Unpolished Roughness (RA) | ~ 50 | ”m | Polycrystalline BDD (PCD) |
| Polished Roughness (RA) | ~ 50 | nm | Polished PCD (pBDD) |
| Operating Temperature Range | 21 to 125 | °C | Cyclic Voltammetry (CV) testing range |
| Operating Pressure | 5 | bar | Applied to prevent electrolyte boiling/bubble formation |
| Electrolyte pH | 7 | N/A | 1 M Phosphate buffer system |
| Highest Activation Energy (EA) | 7.41 x 107 | eV | Unpolished BDDO |
| Lowest Activation Energy (EA) | 5.02 x 107 | eV | Polished BDDH |
| Max ECW (Jcut-off 5.0 mA/cmÂČ) | 2.31 | V | Unpolished BDDO (at 21 °C) |
| Min ECW (Jcut-off 5.0 mA/cmÂČ) | 1.43 | V | Polished BDDO (at 125 °C) |
| Hydrogen Terminated Contact Angle (Polished) | 98 ± 0.5 | ° | Highly hydrophobic surface |
| Oxygen Terminated Contact Angle (Polished) | 36 ± 0.5 | ° | Highly hydrophilic surface |
Key Methodologies
Section titled âKey MethodologiesâThe following steps outline the critical preparation and measurement techniques used to achieve the reported results, focusing on parameters relevant to MPCVD diamond fabrication and processing.
- Material Sourcing and Cutting: Electrochemical grade BDD substrates (10 x 10 x 0.5 mm) were acquired and custom laser cut into 3 mm diameter working electrodes.
- Aggressive Acid Cleaning: Substrates were cleaned at 200 °C for 10 minutes in a highly oxidizing solution (ammonium persulfate and concentrated sulfuric acid) to remove adventitious carbon, hydrocarbons, and graphitic carbon.
- Surface Termination Control:
- Hydrogen (BDDH): Achieved using H-plasma in an MPCVD reactor at 400 °C platen temperature, 700 W power, and 35 Torr pressure for 10 minutes.
- Oxygen (BDDO): Achieved via ozone treatment under 10-6 mbar vacuum for 1 hour.
- Electrode Metalization and Sealing: The 3 mm BDD pieces were metallized with a Ti-Pt-Au stack to ensure robust ohmic contact and soldered to Be-Cu pins. The assembly was sealed into a PEEK bulkhead using high-temperature epoxy (rated to 150 °C).
- Polishing Standardization: Electrodes were polished with 3 ”m diamond slurry on a PSU-M pad before CV measurements to standardize surface quality.
- High-Temperature CV: Cyclic Voltammetry (CV) measurements were conducted in a PEEK flow cell using a 1 M phosphate buffer electrolyte (pH 7) at 5 bar pressure, with temperatures ranging from 21 °C to 125 °C.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research highlights the need for highly customized, high-quality Boron Doped Diamond materials capable of performing reliably under extreme conditions (high temperature, high pressure). 6CCVD is uniquely positioned to supply the exact specifications required to replicate or advance this work.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate the widest electrochemical window observed in this study, researchers require high-quality, heavily doped PCD with minimal spÂČ contamination.
- Heavy Boron Doped PCD (BDD): 6CCVD offers electrochemical grade BDD wafers with doping levels exceeding 1020 atoms/cmÂł, matching the conductivity and performance requirements of the tested material.
- Unpolished/As-Grown PCD: To maximize the electrochemical window (as demonstrated by the unpolished electrodes), 6CCVD can supply PCD wafers in an as-grown state, minimizing surface damage and maintaining a low spÂČ carbon ratio.
- Optical Grade SCD: For applications requiring the absolute highest purity and lowest defect density, 6CCVD offers Single Crystal Diamond (SCD) substrates, which can be heavily boron-doped (BDD) for superior electronic properties and ultra-smooth polishing (Ra < 1 nm).
Customization Potential
Section titled âCustomization PotentialâThe experimental setup relied heavily on custom dimensions and specific metal contacts, areas where 6CCVD provides end-to-end solutions.
| Requirement in Paper | 6CCVD Custom Capability | Benefit to Researcher |
|---|---|---|
| Custom Dimensions | Plates/wafers up to 125 mm (PCD) and custom laser cutting services. | We can supply the initial 10 x 10 x 0.5 mm substrates or directly supply the required 3 mm diameter working electrodes. |
| Metalization Stack | In-house capability for Au, Pt, Pd, Ti, W, Cu. | We can deposit the exact Ti-Pt-Au ohmic contact stack used in this study, ensuring reliable high-temperature performance and carbide formation. |
| Surface Finish Control | Polishing down to Ra < 5 nm (PCD) or Ra < 1 nm (SCD). | We can provide both the highly polished (RA ~ 50 nm) and the rougher, unpolished (RA ~ 50 ”m) surfaces required for comparative studies on spÂČ/spÂł ratio effects. |
| Substrate Thickness | SCD/PCD thickness from 0.1 ”m up to 500 ”m, and substrates up to 10 mm. | We can provide the 0.5 mm thick substrates used, or thicker/thinner materials as required for specific device integration. |
Engineering Support
Section titled âEngineering SupportâThis research confirms that BDD is a robust material for extreme environments, such as high-temperature sensing in oil wells (cited as > 150 °C). 6CCVDâs in-house PhD team specializes in optimizing diamond material properties for these challenging applications.
- High-Temperature Expertise: Our engineers can assist researchers in selecting the optimal BDD material (PCD vs. SCD, doping level, and surface finish) to maximize the electrochemical window and stability for similar high-temperature electrochemistry projects.
- Surface Termination Optimization: We offer controlled H-plasma and O-plasma termination services to tailor the surface chemistry, enabling precise control over hydrophobicity and electrocatalytic properties.
- Global Logistics: We ensure reliable, global shipping (DDU default, DDP available) of sensitive, custom-fabricated diamond electrodes directly to your lab.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract This work compares the electrochemical windows of polished and unpolished boron doped diamond (BDD) electrodes with hydrogen and oxygen terminations at a series of temperatures up to 125 °C. The experiment was run at 5 bar pressure to avoid complications due to bubble formation. An alternative method for determining the electrochemical window is compared to the most commonly used method, which defines the window at an arbitrary current density cut-off (J cut-off ) value. This arbitrary method is heavily influenced by the mass transport of the electrolyte and cannot be used to compare electrodes across literature where different J cut-off values have been used. A linear fit method is described which is less affected by the experimental conditions in a given measurement system. This enables a more accurate comparison of the relative electrochemical window from various diamond electrode types from reported results. Through comparison of polished and unpolished BDD electrodes, with hydrogen and oxygen surface terminations, it is determined that the electrochemical window of BDD electrodes narrows as temperature increases; activation energies are reported.