A Diamond/Graphene/Diamond Electrode for Waste Water Treatment

At a Glance

Metadata	Details
Publication Date	2023-11-29
Journal	Nanomaterials
Authors	Yibao Wang, Zhigang Gai, Fengxiang Guo, Mei Zhang, Lili Zhang
Institutions	Institute of Oceanographic Instrumentation, University of Siegen
Citations	5
Analysis	Full AI Review Included

Technical Documentation & Analysis: DGD Electrodes for High-Efficiency EAOPs

Executive Summary

This research successfully demonstrates a novel Boron-Doped Diamond/Graphene/Diamond (DGD) sandwich electrode structure that significantly enhances the performance and energy efficiency of electrochemical advanced oxidation processes (EAOPs) for wastewater treatment.

Core Achievement: The DGD structure effectively improves electrode conductivity, overcoming the high resistance limitation of conventional BDD electrodes without sacrificing the wide electrochemical window.
Methodology: The DGD electrode was fabricated using Hot Filament Chemical Vapor Deposition (HFCVD) for BDD layers, separated by a multilayer graphene interlayer formed via Cu-metal-assisted vacuum annealing.
Optimized Performance: The DG20D sample (20 min annealing time) exhibited the best results, achieving an interlayer thickness of 21.2 nm and optimal sp²/sp³ carbon ratios.
Energy Efficiency: The energy utilization ratio (Q) for Citric acid degradation was 57.34%, which is 2.4 times higher than that of the single BDD electrode (23.72%).
Reduced Consumption: The energy consumption per unit TOC removal (E_CTOC) for Catechol degradation was reduced to 66.9% of the conventional BDD electrode value.
Commercial Viability: The DGD sandwich electrode is identified as a novel and commercially applicable material for high-efficiency electrocatalytic degradation of organic pollutants, providing new inspiration for high-performance BDD anodes.

Technical Specifications

The following hard data points were extracted from the preparation and performance analysis of the DGD electrodes:

Parameter	Value	Unit	Context
BDD Deposition Method	HFCVD	N/A	Hot Filament Chemical Vapor Deposition
BDD Film Thickness (Bottom Layer)	500	µm	Initial BDD layer thickness
BDD Film Thickness (Upper Layer)	800	nm	Final BDD layer thickness
Boron Doping Concentration	4000	ppm	Standard BDD growth condition
BDD Growth Rate	2.5	µm/h	Standard BDD growth rate
Graphene Annealing Temperature	1000	°C	Cu-metal-assisted vacuum annealing
Optimized Annealing Time (DG20D)	20	min	Yields multilayer graphene interlayer
DG20D Interlayer Thickness	21.2	nm	Measured via TEM
Oxygen Evolution Potential (OEP) - DG20D	2.37	V	Higher than BDD (2.1 V), indicating wider electrochemical window
Step Current Density Increase (DG20D vs BDD)	1.35	Times	Degradation of Citric Acid (CA)
Energy Utilization Ratio (Q) - DG20D	57.34	%	2.4 times that of BDD (23.72%) for CA degradation
E_CTOC Reduction (Catechol) - DG20D	66.9	% of BDD	Lowest energy consumption achieved
Current Density (Electrolysis)	200	mA/cm²	Standard test condition
Electrolytic Voltage Range	6.5 to 7.5	V	Varies based on electrode structure

Key Methodologies

The DGD sandwich structure was fabricated using a multi-step MPCVD and metal-assisted thermal process:

Bottom BDD Layer Growth:
- System: Hot Filament Chemical Vapor Deposition (HFCVD).
- Substrate: Si (100).
- Parameters: Base temperature 850 °C, hot wire temperature 2400-2500 °C, 4000 ppm boron doping.
- Result: 500 µm thick BDD film.
Copper Deposition:
- Method: Physical Vapor Deposition (PVD).
- Thickness: 300 nm Cu layer deposited onto the BDD surface.
Graphene Interlayer Formation:
- Method: Copper-metal-assisted vacuum annealing.
- Parameters: Annealing temperature 1000 °C. Optimized time was 20 minutes (DG20D).
- Mechanism: Induces multilayer graphene formation via catalytic conversion.
Upper BDD Layer Growth:
- Method: HFCVD (parameters consistent with the bottom layer).
- Thickness: 800 nm BDD film deposited over the graphene layer, completing the DGD sandwich.
Electrochemical Testing:
- Techniques: Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), and current density-time curves (3 V applied potential).
- Application: Used to determine OEP, mobility, and mass transfer resistance.
Electrocatalytic Degradation:
- Target Pollutants: Citric acid (CA), Catechol, and Tetracycline hydrochloride (TCH) at 100 mg/L.
- Setup: DGD anode, Ti cathode, 3 mm electrode distance.
- Metrics: Total Organic Carbon (TOC) removal and Energy consumption per unit TOC removal (E_CTOC).

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the advanced diamond materials and custom fabrication services required to replicate, optimize, and scale the high-performance DGD electrode technology for commercial EAOP applications.

Research Requirement	6CCVD Applicable Materials & Services	Technical Sales Advantage
High-Conductivity BDD Films	Heavy Boron-Doped PCD (Polycrystalline Diamond)	We provide high-quality, heavily doped BDD films grown via MPCVD, ensuring the low resistivity and wide electrochemical window essential for high-efficiency EAOPs. We control doping up to 10,000 ppm.
Custom Layer Thicknesses	Precision Thickness Control (0.1µm - 500µm)	The DGD structure requires precise control over the 500 µm bottom layer and the 800 nm top layer. 6CCVD offers custom thickness specifications for both SCD and PCD films. Substrates up to 10mm are available.
Graphene Interlayer Formation	Custom Metalization & Thermal Processing	The critical step involves Cu deposition (300 nm) followed by high-temperature annealing. 6CCVD offers in-house metalization capabilities including Cu, Ti, Pt, Pd, Au, and W, allowing clients to integrate the metal-assisted graphene growth step seamlessly.
Scaling Electrode Size	PCD Wafers up to 125mm Diameter	To transition this research from lab-scale (15 mm x 10 mm) to industrial application, large-area electrodes are necessary. 6CCVD specializes in producing inch-size Polycrystalline Diamond (PCD) wafers up to 125mm in diameter.
Surface Preparation	Ultra-Low Roughness Polishing	Consistent surface quality is vital for uniform metal deposition and subsequent layer growth. We guarantee polishing down to Ra < 5nm for inch-size PCD, ensuring optimal starting surfaces for DGD fabrication.
Global Supply Chain	Global Shipping (DDU/DDP)	We ensure reliable, fast delivery of custom diamond materials worldwide, simplifying logistics for international research and development teams.

Engineering Support

6CCVD’s in-house PhD team specializes in optimizing diamond material properties for electrochemical applications. We offer consultation services to assist engineers and scientists in selecting the optimal BDD doping concentration, layer thickness ratios, and metalization schemes required to maximize the E_CTOC reduction and energy efficiency for similar Electrochemical Advanced Oxidation Processes (EAOPs) projects.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Boron-doped diamond (BDD) thin film electrodes have great application potential in water treatment. However, the high electrode energy consumption due to high resistance directly limits the application range of existing BDD electrodes. In this paper, the BDD/graphene/BDD (DGD) sandwich structure electrode was prepared, which effectively improved the conductivity of the electrode. Meanwhile, the sandwich electrode can effectively avoid the degradation of electrode performance caused by the large amount of non-diamond carbon introduced by heavy doping, such as the reduction of the electrochemical window and the decrease of physical and chemical stability. The microstructure and composition of the film were characterized by scanning electron microscope (SEM), atomic force microscopy (AFM), Raman spectroscopy, and transmission electron microscopy (TEM). Then, the degradation performance of citric acid (CA), catechol, and tetracycline hydrochloride (TCH) by DGD electrodes was systematically studied by total organic carbon (TOC) and Energy consumption per unit TOC removal (ECTOC). Compared with the single BDD electrode, the new DGD electrode improves the mobility of the electrode and reduces the mass transfer resistance by 1/3, showing better water treatment performance. In the process of dealing with Citric acid, the step current of the DGD electrode was 1.35 times that of the BDD electrode, and the energy utilization ratio of the DGD electrode was 2.4 times that of the BDD electrode. The energy consumption per unit TOC removal (ECTOC) of the DGD electrode was lower than that of BDD, especially Catechol, which was reduced to 66.9% of BDD. The DGD sandwich electrode, as a new electrode material, has good electrochemical degradation performance and can be used for high-efficiency electrocatalytic degradation of organic pollutants.

Tech Support

Original Source

DOI: https://doi.org/10.3390/nano13233043

References

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