Construction of Z-Scheme TiO2/Au/BDD Electrodes for an Enhanced Electrocatalytic Performance

At a Glance

Metadata	Details
Publication Date	2023-01-16
Journal	Materials
Authors	Kai Zhang, Kehao Zhang, Yuxiang Ma, Hailong Wang, Junyong Shao
Institutions	Luoyang Institute of Science and Technology, Zhengzhou Institute of Machinery
Citations	9
Analysis	Full AI Review Included

Technical Documentation & Analysis: Z-Scheme $\text{TiO}_{2}/\text{Au}/\text{BDD}$ Electrodes

Executive Summary

This research successfully demonstrates the fabrication and enhanced performance of a Z-scheme $\text{TiO}_{2}/\text{Au}/\text{BDD}$ composite electrode for photo-electrocatalytic wastewater treatment.

Core Achievement: The optimal $\text{TiO}_{2}/\text{Au}/\text{BDD-30}$ electrode achieved a 98% decolorization rate of Reactive Brilliant Red X-3B in just 30 minutes under photo-electrocatalytic conditions, significantly outperforming the bare BDD (75%).
Mechanism Validation: The sandwich structure ($\text{TiO}_{2}/\text{Au}/\text{BDD}$) successfully formed an all-solid Z-scheme, utilizing Au as an electron mediator to create an Ohmic contact with low resistance.
Carrier Transport Enhancement: The introduction of the Au layer boosted the Hall mobility of the electrode from $158 \text{ cm}^{2}/\text{V}\cdot\text{s}$ (bare BDD) to $194 \text{ cm}^{2}/\text{V}\cdot\text{s}$ ($\text{TiO}_{2}/\text{Au}/\text{BDD-30}$).
Improved Efficiency: The enhanced carrier separation and transport resulted in a lower Oxygen Evolution Potential (1.56 V vs. SHE) compared to bare BDD (1.75 V vs. SHE), indicating improved energy efficiency.
Material Integrity: Raman spectroscopy confirmed that the high-temperature post-treatment ($450^{\circ}\text{C}$) did not induce significant graphitization of the BDD film, preserving its electrochemical stability.

Technical Specifications

Parameter	Value	Unit	Context
Optimal Au Sputtering Time	30	s	For $\text{TiO}_{2}/\text{Au}/\text{BDD-30}$ electrode
Post-Deposition Heat Treatment	450	°C	For 1 hour, to obtain anatase $\text{TiO}_{2}$
DC Bias Voltage (EPD)	40	V	Electrophoretic deposition of $\text{TiO}_{2}$
Constant Applied Current	0.6	A	Simulated wastewater degradation experiment
Decolorization Rate (Optimal)	98	%	$\text{TiO}_{2}/\text{Au}/\text{BDD-30}$ after 30 min (Photo-EC)
Hall Mobility (Bare BDD)	158	$\text{cm}^{2}/\text{V}\cdot\text{s}$	Baseline carrier transport efficiency
Hall Mobility ($\text{TiO}_{2}/\text{Au}/\text{BDD-30}$)	194	$\text{cm}^{2}/\text{V}\cdot\text{s}$	Enhanced by Au Ohmic contact layer
Sheet Resistivity ($\text{TiO}_{2}/\text{Au}/\text{BDD-30}$)	0.143	$\Omega\text{m}$	Lower than bare BDD ($0.175 \Omega\text{m}$)
Oxygen Evolution Potential (OEP)	1.56	V	$\text{TiO}_{2}/\text{Au}/\text{BDD-30}$ (vs. Standard Hydrogen Electrode, SHE)
BDD Diamond Peak (Raman)	1331.65	$\text{cm}^{-1}$	Confirms high-quality diamond structure

Key Methodologies

The Z-scheme $\text{TiO}_{2}/\text{Au}/\text{BDD}$ composite electrodes were fabricated using a precise, multi-step deposition process:

Substrate Preparation: Silicon-based Boron-Doped Diamond (BDD) electrodes were cleaned ultrasonically using acetone, absolute ethanol, and deionized water.
Au Interlayer Deposition: Gold (Au) was deposited onto the oven-dried BDD surface via ion sputtering.
- Sputtering Parameters: Current set at 4 mA.
- Loading Control: Au content was controlled by varying the sputtering time (30 s, 60 s, and 90 s).
$\text{TiO}_{2}$ Sol Preparation: Tetrabutyl titanate (TBOT) was mixed with absolute alcohol. A separate mixture of deionized water and ethanol was added dropwise, and the pH was adjusted to 3 using glacial acetic acid.
$\text{TiO}_{2}$ Deposition (Electrophoretic Deposition, EPD): The $\text{Au}/\text{BDD}$ electrode was used as the cathode and graphite as the anode in the $\text{TiO}_{2}$ sol.
- EPD Parameters: 40 V DC bias applied for 60 s. The deposition process was repeated three times.
Thermal Post-Treatment: The resulting electrode was immediately heated at $450^{\circ}\text{C}$ for 1 hour to crystallize the $\text{TiO}_{2}$ into the anatase phase and ensure adhesion.

6CCVD Solutions & Capabilities

This research highlights the critical role of high-quality Boron-Doped Diamond (BDD) substrates and precise metalization techniques in achieving high-performance electrocatalytic systems. 6CCVD is uniquely positioned to supply the foundational materials and custom processing required to replicate and scale this Z-scheme technology.

Applicable Materials

To replicate or advance this high-efficiency electrocatalytic system, researchers require highly conductive, stable diamond films:

Heavy Boron-Doped PCD (Polycrystalline Diamond): 6CCVD offers highly conductive PCD films (up to 500 µm thick) suitable for large-scale anode applications like industrial wastewater treatment. Our PCD films can be supplied in custom dimensions up to 125 mm wafers, enabling direct scale-up from lab prototypes.
Boron-Doped SCD (Single Crystal Diamond): For applications requiring ultra-low defect density, superior thermal management, or highly uniform surface morphology (critical for consistent thin-film deposition like EPD), 6CCVD supplies high-quality SCD films (0.1 µm to 500 µm).

Customization Potential

The success of the $\text{TiO}_{2}/\text{Au}/\text{BDD}$ electrode hinges on the precise control of the Au interlayer, which acts as the charge transport mediator. 6CCVD offers comprehensive in-house services to optimize this critical interface:

Research Requirement	6CCVD Capability & Advantage	Technical Benefit
BDD Substrate Dimensions	Custom plates/wafers up to 125 mm (PCD) and custom SCD sizes. Substrate thickness up to 10 mm.	Enables industrial scale-up of the electrocatalytic reactor design.
Au Interlayer Deposition	Internal metalization capability: Au, Pt, Pd, Ti, W, Cu. We offer precise control over thin-film thickness via sputtering or e-beam evaporation.	Allows researchers to fine-tune the Ohmic contact layer thickness (replicating the optimal 30s sputtering result) or explore alternative Z-scheme mediators (e.g., Pt, Pd).
Surface Quality	Polishing services: Ra < 1 nm (SCD) and Ra < 5 nm (Inch-size PCD).	Provides an ultra-smooth, uniform base for subsequent $\text{TiO}_{2}$ electrophoretic deposition (EPD), improving adhesion and reducing contact resistance variability.
Material Integration	We supply BDD films already mounted on Si or other custom substrates, ready for immediate thin-film processing (sputtering/EPD).	Reduces preparation time and ensures material compatibility for complex composite electrode fabrication.

Engineering Support

6CCVD’s in-house PhD team specializes in diamond material science and electrochemical applications. We provide expert consultation for projects focused on Advanced Oxidation Processes (AOPs), Electrocatalysis, and Photo-Electrochemical Systems.

Our engineers can assist in selecting the optimal boron doping level and diamond morphology (SCD vs. PCD) to maximize the intrinsic conductivity and stability required for high-current density wastewater treatment applications.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. Global shipping is available (DDU default, DDP available).

View Original Abstract

TiO2/Au/BDD composites with a Z-scheme structure was prepared by orderly depositing gold (Au) and titanium dioxide (TiO2) on the surface of a boron-doped diamond (BDD) film using sputtering and electrophoretic deposition methods. It was found that the introduction of Au between TiO2 and the BDD, not only could reduce their contact resistance, to increase the carrier transport efficiency, but also could improve the surface Hall mobility of the BDD electrode. Meanwhile, the designed Z-scheme structure provided a fast channel for the electrons and holes combination, to promote the effective separation of the electrons and holes produced in TiO2 and the BDD under photoirradiation. The electrochemical characterization elucidated that these modifications of the structure obviously enhanced the electrocatalytic performance of the electrode, which was further verified by the simulated wastewater degradation experiments with reactive brilliant red X-3B. In addition, it was also found that the photoirradiation effectively enhanced the pollution degradation efficiency of the modified electrode, especially for the TiO2/Au/BDD-30 electrode.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma16020868

References

2015 - “Omics” Insights into PAH Degradation toward Improved Green Remediation Biotechnologies [Crossref]
2015 - Single and Coupled Electrochemical Processes and Reactors for the Abatement of Organic Water Pollutants: A Critical Review [Crossref]
2014 - Electrochemical advanced oxidation processes: Today and tomorrow. A review [Crossref]
2016 - Electrochemical technologies for wastewater treatment and resource reclamation [Crossref]
2013 - Removal of residual anti-inflammatory and analgesic pharmaceuticals from aqueous systems by electrochemical advanced oxidation processes. A review [Crossref]
2014 - Critical review of electrochemical advanced oxidation processes for water treatment applications [Crossref]
2014 - Recent updates on electrochemical degradation of bio-refractory organic pollutants using BDD anode: A mini review [Crossref]
2017 - Electrochemical advanced oxidation processes: A review on their application to synthetic and real wastewaters [Crossref]
2015 - Recent developments of electro-oxidation in water treatment—A review [Crossref]
2014 - Advanced Oxidation Processes in Water/Wastewater Treatment: Principles and Applications. A Review [Crossref]