Visible-Light Activation of Photocatalytic for Reduction of Nitrogen to Ammonia by Introducing Impurity Defect Levels into Nanocrystalline Diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-10-14 |
| Journal | Materials |
| Authors | Rui Su, Zhangcheng Liu, Haris Naeem Abbasi, Jinjia Wei, Hongxing Wang |
| Institutions | Xiâan Jiaotong University |
| Citations | 5 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Visible-Light Activated Photocatalytic Diamond
Section titled âTechnical Documentation & Analysis: Visible-Light Activated Photocatalytic DiamondâThis document analyzes the research paper âVisible-Light Activation of Photocatalytic for Reduction of Nitrogen to Ammonia by Introducing Impurity Defect Levels into Nanocrystalline Diamondâ and outlines how 6CCVDâs advanced MPCVD diamond capabilities can support and extend this critical research in sustainable ammonia synthesis.
Executive Summary
Section titled âExecutive SummaryâThe research successfully demonstrates a high-efficiency, visible-light-activated photocatalytic system for converting nitrogen (N2) to ammonia (NH3) using nitrogen-doped nanocrystalline diamond (NDD).
- Core Achievement: NDD films, synthesized via MPCVD, achieved an ammonia production rate of 6.27 ± 1.48 nmol/cm2·h, significantly surpassing undoped polycrystalline diamond (PD) and single crystal diamond (SCD).
- Mechanism: Nitrogen doping introduces intermediate energy levels (specifically the Nitrogen Vacancy, NV- and NV0 centers) within the diamondâs forbidden bandgap.
- Key Advantage: These defect levels enable efficient internal photoemission, allowing the photocatalytic reaction to proceed under sub-band gap (visible) light ($\lambda$ > 225 nm), overcoming the high energy barrier of intrinsic diamond (5.45 eV).
- Material Requirement: The superior performance relies on precise control over nitrogen incorporation and the formation of a high-surface-area nanocrystalline structure (grains > 10 nm).
- 6CCVD Value Proposition: 6CCVD specializes in custom MPCVD diamond materials, offering the precise doping control, thickness uniformity (down to 0.1 ”m), and large-area PCD substrates necessary to scale and optimize this energy-efficient ammonia synthesis technology.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the research paper, highlighting the material properties and performance metrics of the tested diamond films.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| NDD Ammonia Synthesis Rate | 6.27 ± 1.48 | nmol/cm2·h | Highest rate achieved under 200-800 nm illumination |
| SCD Ammonia Synthesis Rate | 2.53 ± 0.16 | nmol/cm2·h | Undoped single crystal diamond film performance |
| Diamond Bandgap Energy | 5.45 | eV | Intrinsic excitation threshold ($\lambda$ < 225 nm) |
| NV- Zero Phonon Line (ZPL) | 1.945 (637) | eV (nm) | Negatively charged nitrogen vacancy state |
| NV0 Zero Phonon Line (ZPL) | 2.156 (575) | eV (nm) | Neutral nitrogen vacancy state |
| NDD Film Thickness (Active Layer) | 200 | nm | Nitrogen-doped nanocrystalline layer |
| NDD Average Grain Diameter | > 10 | nm | Nanocrystalline structure |
| Photocatalysis Wavelength Range | 200-800 | nm | Used 450 W high-pressure Hg/Xe lamp |
Key Methodologies
Section titled âKey MethodologiesâThe experiment relied on precise MPCVD growth parameters to achieve the desired nanocrystalline structure and nitrogen doping levels.
| Step | Parameter | Value | Context |
|---|---|---|---|
| Substrate | Material | 2-inch Si | Used for polycrystalline growth |
| Nucleation Method | Seeding | Nanodiamond particles (5-8 nm) | Sonication in ethanol for 15 min |
| MPCVD System | Equipment | Modified AsTex system | Used for all diamond deposition |
| Growth Temperature | Tgrowth | 1000 | °C |
| Total Gas Flow Rate | Flow | 500 | sccm |
| Polycrystal Layer Thickness | Thickness | 3 | ”m |
| NDD Layer Thickness | Thickness | 200 | nm |
| NDD Doping Gas Ratio | N2/H2 Ratio | 1% | Introduced during the final 200 nm growth step |
| Polycrystal Gas Ratio | CH4/H2 Ratio | 4% | Used for the 3 ”m base layer |
| Microwave Power (NDD/PD) | PMW | 2000 | W |
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe successful replication and scaling of this high-efficiency photocatalytic process require precise control over material structure, thickness, and impurity dopingâall core competencies of 6CCVD.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate or extend the performance of the Nitrogen-Doped Nanocrystalline Diamond (NDD) used in this study, 6CCVD recommends the following materials:
- Nitrogen-Doped Polycrystalline Diamond (PCD):
- Requirement Match: This material directly corresponds to the NDD film synthesized. 6CCVD offers precise control over nitrogen gas flow (N2/H2 ratio) during MPCVD growth to tune the concentration of NV centers, optimizing the visible-light absorption peaks (575 nm and 637 nm).
- Structure Control: We can tailor the grain size to optimize the active site density, crucial for maximizing the N2 reduction rate (6.27 nmol/cm2·h).
- Optical Grade Single Crystal Diamond (SCD):
- Requirement Match: For contrast studies or applications requiring superior thermal management and surface flatness (Ra < 1 nm), 6CCVD provides high-purity SCD substrates and homoepitaxial layers.
- Custom Boron-Doped Diamond (BDD):
- Extension Potential: While this paper focused on N-doping, BDD is known for its exceptional electrochemical properties and stability. 6CCVD can provide heavy Boron-Doped PCD or SCD for comparative studies in electrocatalytic NRR, offering a large electrochemical potential window.
Customization Potential
Section titled âCustomization PotentialâThe research utilized specific film dimensions (200 nm active layer) and growth on 2-inch substrates. 6CCVDâs manufacturing capabilities are ideally suited to meet and exceed these requirements:
| Research Requirement | 6CCVD Capability | Advantage for Replication/Scaling |
|---|---|---|
| Substrate Size | Plates/wafers up to 125 mm (PCD) | Enables scaling from 2-inch lab samples to industrial wafer sizes. |
| Active Layer Thickness | SCD/PCD thickness control from 0.1 ”m to 500 ”m | Perfect control over the critical 200 nm active layer thickness used in the study. |
| Doping Control | Precise gas flow management (N2, B) | Allows fine-tuning of NV center concentration for maximum photocatalytic efficiency. |
| Surface Finish | Polishing to Ra < 5 nm (Inch-size PCD) | Ensures reproducible surface quality for consistent photocatalytic testing. |
| Metalization | Internal capability (Au, Pt, Pd, Ti, W, Cu) | Available for integrating diamond films into complex reactor systems or creating electrode structures for photoelectrochemical NRR extensions. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists and engineers can provide authoritative support for projects focused on Photocatalytic Nitrogen Reduction and Quantum Defect Engineering. We assist researchers in selecting the optimal diamond material (PCD vs. SCD), determining the necessary doping concentration (N-doping for NV centers), and specifying the required surface termination and thickness to maximize visible-light activation and NRR yield.
Global Shipping: We ensure reliable, global delivery of custom diamond materials, with DDU as the default and DDP available upon request.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Nitrogen impurity has been introduced in diamond film to produce a nitrogen vacancy center (NV center) toward the solvated electron-initiated reduction of N2 to NH3 in liquids, giving rise to extend the wavelength region beyond the diamondâs band. Scanning electron microscopy and X-ray diffraction demonstrate the formation of the nanocrystalline nitrogen-doped diamond with an average diameter of ten nanometers. Raman spectroscopy and PhotoLuminescence (PL) spectrum show characteristics of the NV0 and NVâ charge states. Measurements of photocatalytic activity using supraband (λ < 225 nm) gap and sub-band gap (λ > 225 nm) excitation show the nitrogen-doped diamond significantly enhanced the ability to reduce N2 to NH3 compared to the polycrystalline diamond and single crystal diamond (SCD). Our results suggest an important process of internal photoemission, in which electrons are excited from negative charge states into conduction band edges, presenting remarkable photoinitiated electrons under ultraviolet and visible light. Other factors, including transitions between defect levels and processes of reaction, are also discussed. This approach can be especially advantageous to such as N2 and CO2 that bind only weakly to most surfaces and high energy conditions.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
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