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6CCVD Research

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

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2023-01-16
JournalMaterials
AuthorsKai Zhang, Kehao Zhang, Yuxiang Ma, Hailong Wang, Junyong Shao
InstitutionsZhengzhou Institute of Machinery, Zhengzhou University
Citations9
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

This research details the fabrication and performance analysis of a novel Z-scheme TiO2/Au/BDD composite electrode designed for enhanced photo-electrocatalytic wastewater treatment.

  • Core Innovation: Construction of a sandwich-type Z-scheme structure (TiO2/Au/BDD) using gold (Au) as an electron mediator layer between the Boron-Doped Diamond (BDD) substrate and the Titanium Dioxide (TiO2) layer.
  • Fabrication Method: Au was deposited via ion sputtering, followed by TiO2 deposition via electrophoretic deposition (EPD) and subsequent annealing.
  • Performance Enhancement: The Au layer significantly improved the electrode’s performance by forming an Ohmic contact, which reduced contact resistance and provided a fast channel for carrier transport.
  • Z-Scheme Mechanism: The Z-scheme structure promotes the effective separation of photo-induced electrons (e-) and holes (h+) generated in the TiO2 and BDD, boosting the electrocatalytic redox performance.
  • Optimal Configuration: The TiO2/Au/BDD-30 electrode (30 seconds Au sputtering time) exhibited the best overall electrochemical properties and degradation efficiency.
  • Wastewater Degradation: Under photo-electrocatalytic synergy, the TiO2/Au/BDD-30 electrode achieved a 98% removal rate of Reactive Brilliant Red X-3B in 30 minutes, significantly surpassing the 75% removal rate of the bare BDD electrode.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Optimal Au Sputtering Time30sFor TiO2/Au/BDD-30 electrode
Au Sputtering Current4mAIon sputtering process
Electrophoretic Deposition Voltage40VDC bias applied for TiO2 deposition
Annealing Temperature450°CPost-deposition heat treatment (1 h)
Bare BDD Hall Mobility158cm2/V·sReference measurement
TiO2/Au/BDD-30 Hall Mobility194cm2/V·sIncreased mobility due to Au layer
TiO2/Au/BDD-30 Sheet Resistivity0.143ΩmLower than bare BDD (0.175 Ωm)
TiO2/Au/BDD-30 Sheet Carrier Conc.2.25 x 1017cm-2Near optimal carrier concentration
Wastewater Concentration200mg/LReactive Brilliant Red X-3B
Electrolyte Concentration100mMNa2SO4 aqueous solution
Applied Current (Electrolysis)0.6AConstant current batch reactor operation
Decolorization Rate (30 min, Photo-assisted)98%TiO2/Au/BDD-30 performance
Decolorization Rate (30 min, Bare BDD)75%Reference performance (without light)
Potential Window (Neutral, TiO2/Au/BDD-30)2.16Vvs. Standard Hydrogen Electrode (SHE)
Raman Diamond Peak1331.65cm-1Characteristic diamond peak (standard 1332 cm-1)

Key Methodologies

Section titled “Key Methodologies”

The composite electrode fabrication involved a precise, multi-step process combining physical vapor deposition and solution-based techniques:

  1. Substrate Preparation: Silicon-based BDD electrodes were cleaned sequentially using ultrasonic baths of acetone, absolute ethanol, and deionized water.
  2. Gold (Au) Deposition: Au was deposited onto the dry BDD surface using an ion sputtering apparatus (SBC-12).
    • Sputtering current was maintained at 4 mA.
    • Deposition times were varied (30 s, 60 s, 90 s) to control Au loading, resulting in TiO2/Au/BDD-30, -60, and -90 samples.
  3. TiO2 Sol Preparation: Tetrabutyl titanate (TBOT) and absolute alcohol were mixed and stirred. Deionized water and absolute ethanol were added dropwise, and the pH was adjusted to 3 using glacial acetic acid.
  4. Electrophoretic Deposition (EPD): The Au/BDD electrode served as the cathode, and a graphite rod served as the anode, immersed in the TiO2 sol.
    • A DC bias of 40 V was applied for 60 seconds per cycle.
    • The deposition process was repeated three times to achieve the desired TiO2 film thickness.
  5. Annealing: Immediately following EPD, the electrodes were heated at 450 °C for 1 hour to crystallize the TiO2 into the anatase phase and ensure good adhesion.
  6. Characterization: Electrodes were analyzed using X-ray Diffraction (XRD) and Laser Raman Spectroscopy for phase composition, Field-Emission Scanning Microscopy (FESEM) with Energy Dispersive Spectroscopy (EDS) for morphology and element distribution, Hall measurement for carrier properties, and Cyclic Voltammetry (CV) for electrochemical windows and redox properties.
  7. Performance Testing: Photo-electrocatalytic degradation was performed in a batch reactor using a Xe lamp (simulated solar light) and a constant current (0.6 A) to degrade Reactive Brilliant Red X-3B.

Commercial Applications

Section titled “Commercial Applications”

The enhanced performance and synergistic mechanism achieved by the Z-scheme TiO2/Au/BDD electrode are highly relevant to several high-value engineering and environmental sectors:

  • Industrial Wastewater Treatment: Highly efficient mineralization of recalcitrant organic pollutants (e.g., dyes, pharmaceuticals, pesticides) in industrial effluents, leveraging the high oxidation power of BDD combined with photocatalysis.
  • Advanced Oxidation Processes (AOPs): Implementation in hybrid photo-electrochemical reactors where the synergy between light and electricity maximizes the production of hydroxyl radicals (‱OH) and other reactive species.
  • Water Reclamation and Reuse: Use as durable, high-performance anodes in electrochemical cells designed for treating complex water streams for subsequent reuse, reducing reliance on chemical additives.
  • Electrochemical Sensing and Biosensors: BDD substrates are known for their wide potential window and low background current; the Au/TiO2 modification could enhance sensitivity and selectivity for specific analytes under photo-activation.
  • Electrochemical Synthesis: Potential application in electro-synthesis processes requiring highly active and stable electrode surfaces for redox reactions.
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

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2015 - “Omics” Insights into PAH Degradation toward Improved Green Remediation Biotechnologies [Crossref]
  2. 2015 - Single and Coupled Electrochemical Processes and Reactors for the Abatement of Organic Water Pollutants: A Critical Review [Crossref]
  3. 2014 - Electrochemical advanced oxidation processes: Today and tomorrow. A review [Crossref]
  4. 2016 - Electrochemical technologies for wastewater treatment and resource reclamation [Crossref]
  5. 2013 - Removal of residual anti-inflammatory and analgesic pharmaceuticals from aqueous systems by electrochemical advanced oxidation processes. A review [Crossref]
  6. 2014 - Critical review of electrochemical advanced oxidation processes for water treatment applications [Crossref]
  7. 2014 - Recent updates on electrochemical degradation of bio-refractory organic pollutants using BDD anode: A mini review [Crossref]
  8. 2017 - Electrochemical advanced oxidation processes: A review on their application to synthetic and real wastewaters [Crossref]
  9. 2015 - Recent developments of electro-oxidation in water treatment—A review [Crossref]
  10. 2014 - Advanced Oxidation Processes in Water/Wastewater Treatment: Principles and Applications. A Review [Crossref]

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