Skip to content
6CCVD Research

Progress in Preparation and Application of Titanium Sub-Oxides Electrode in Electrocatalytic Degradation for Wastewater Treatment

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2022-06-06
JournalCatalysts
AuthorsSiyuan Guo, Zhicheng Xu, Wenyu Hu, Duowen Yang, Xue Wang
InstitutionsXi’an Jiaotong University
Citations33
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

The following summarizes the progress in utilizing Magnéli phase Titanium Sub-Oxides (TinO2n-1, primarily Ti4O7) as high-performance anodes for electrocatalytic oxidation (EO) in wastewater treatment.

  • Superior Anode Material: Ti sub-oxides, particularly Ti4O7, are characterized as ideal anode materials due to their unique crystal structure, high conductivity (up to 1995 S·cm-1), and wide electrochemical stability window (nearly 4 V).
  • Performance Advantage: Ti4O7 anodes exhibit a high Oxygen Evolution Potential (OEP) of 2.28 V (vs. Ag/AgCl), promoting the generation of highly oxidative hydroxyl radicals (‱OH) necessary for deep mineralization, surpassing many commercial DSA electrodes.
  • Stability and Durability: The material demonstrates exceptional physical and chemical stability, offering high corrosion resistance (mass loss < 0.3% after 350 h in HF electrolyte) and a long accelerated service life (31.2 h), addressing key failure modes of traditional Ti-based electrodes.
  • Preparation Routes: Electrodes are successfully prepared via high-temperature methods, including Plasma Spraying (for coated electrodes) and Powder Sintering (for integrated electrodes), yielding dense, highly active, and macroporous structures.
  • High Degradation Efficiency: Ti4O7 systems achieve rapid and high removal rates for refractory pollutants, including 91.7% COD removal for Methyl Orange and 97.95% degradation of Tetracycline (TC) within 3 hours.
  • System Integration Potential: The Ti4O7 anode is highly effective when coupled with advanced techniques like Electro-Fenton or Ultrasonic enhancement, significantly boosting the degradation kinetics and overall energy efficiency of the treatment process.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Electrical Conductivity (Ti4O7)1035S·cm-1Measured at 298 K.
Highest Measured Conductivity (Ti4O7)1995S·cm-1Measured at 298 K (using specific preparation method).
Electrical Conductivity (Graphite)727S·cm-1Comparison baseline.
Electrochemical Window (Ti4O7)~4VDifference between OEP and HEP in 1.0 M H2SO4.
Oxygen Evolution Potential (OEP) (Ti4O7)2.28V vs. Ag/AgClHigh potential for radical generation.
Accelerated Life (Ti4O7)31.2hIn 1 M H2SO4, 1 A·cm-2 current density.
Corrosion Resistance (Ti4O7)0.29% mass lossAfter 350 h in HF electrolyte.
COD Removal (Methyl Orange)91.7%Current density 10 mA·cm-2, 100 mg·L-1 initial concentration.
TC Degradation Rate97.95%Within 3 h, current density 10 mA·cm-2.
SMR Removal (Electro-Fenton/AO)99.48%After 8 h treatment in coupled system.
Phenol Degradation Rate92.22%Within 3 h, 12 V, pH 3.0.
Powder Sintering Temperature1350°CVacuum sintering for integrated Ti4O7 electrode.
Plasma Spraying Current700AUsed for coating Ti4O7 particles onto Ti substrate.
Ti4O7 Coating Particle Size200-300nmFor coating reduction method on Al2O3 matrix.

Key Methodologies

Section titled “Key Methodologies”

The preparation of high-performance titanium sub-oxide electrodes relies on controlling the reduction of TiO2 and optimizing the deposition technique.

  1. Ti Sub-Oxide Powder Synthesis:

    • Precursor: Titanium dioxide (TiO2) is the primary raw material.
    • Methods: Carbothermal reduction (e.g., 1025 °C in N2), Hydrogen reduction (e.g., 1050 °C in H2), or Metallothermic reduction (e.g., annealing at 1333-1353 K in Ar).
    • Goal: Produce MagnĂ©li phase TinO2n-1 powder, typically Ti4O7, with high purity.

  2. Coated Electrode Preparation (Plasma Spraying):

    • Process: Ti4O7 powder is sprayed onto a pretreated conductive substrate (Ti mesh, Ti plate) using ultra-high temperature plasma.
    • Conditions: High current (e.g., 700 A) and inert gas (Ar/H2 mix) are used to ensure fast particle jetting and compact coating density.
    • Result: A Ti/Ti4O7 electrode with a large electrochemically active surface area and strong adhesion.

  3. Integrated Electrode Preparation (Powder Sintering):

    • Process: Ti4O7 nanopowder is mixed with a binder (which volatilizes during heating), pressed into a mold (e.g., 60 MPa), and sintered.
    • Conditions: High vacuum and high temperature (e.g., 1350 °C for 11 h) are applied to achieve a pure, stable, and uniformly integrated ceramic structure.
    • Result: Macroporous Ti4O7 ceramic-integrated electrode with high porosity (e.g., 21.6%) and ultra-high OEP.

  4. Membrane Electrode Preparation (Hydrothermal Reduction):

    • Process: Tubular TiO2 ultrafiltration membranes are subjected to hydrothermal reduction.
    • Conditions: High temperature (e.g., 1050 °C) in a H2 atmosphere for extended periods (30-50 h).
    • Result: Tubular Ti4O7 membrane electrodes suitable for flow-through reactors, offering low internal resistance and good stability.

  5. Composite Electrode Modification:

    • Doping: Ti4O7 is doped with active metals (e.g., Pt, Pd, Ce3+) or used as a conductive carrier for other catalysts (e.g., MoS2, LiNi0.8Co0.15Al0.05O2).
    • Purpose: Enhance electrocatalytic activity, improve charge transfer, and increase the number of active sites, particularly for specific reactions like HER or PFOS degradation.

Commercial Applications

Section titled “Commercial Applications”

The unique combination of high conductivity, stability, and catalytic activity makes Ti sub-oxide electrodes highly valuable across several industrial and environmental sectors.

  • Industrial Wastewater Treatment:
    • Coking and Coal Gasification Effluent: Demonstrated advantages in COD and TOC removal compared to traditional Ti/RuO2-IrO2 anodes.
    • Printing and Dyeing Wastewater: Ti4O7 membrane electrodes achieve high COD removal (up to 96.07%) with reduced energy consumption, suitable for small-scale decentralized systems.
  • Pharmaceutical and Medical Wastewater:
    • Antibiotic Degradation: Highly effective mineralization of refractory antibiotics (e.g., Sulfamerazine, Tetracycline) and simultaneous removal of associated antibiotic resistance genes (ARGs).
    • Phenolic Pollutant Removal: Efficient degradation of toxic compounds like p-nitrophenol and 4-chlorophenol.
  • Advanced Oxidation Processes (AOPs):
    • Coupled Systems: Used as the stable, high-OEP anode in integrated Electro-Fenton, Photoelectrochemical (PEC), and Ultrasonic-enhanced EO systems to maximize the yield and utilization rate of hydroxyl radicals.
  • Electrochemical Manufacturing and Energy:
    • Electrowinning: Used in Al-based composite coating electrodes for electrowinning of nonferrous metals.
    • Energy Storage: Ti4O7 serves as a conductive additive in high-capacity cathode materials (e.g., LiNi0.8Co0.15Al0.05O2) to improve cycling performance and conductivity.
    • Hydrogen Evolution Reaction (HER): Used as a support material for catalysts (e.g., MoS2/Ti4O7) to enhance HER activity due to strong interfacial interaction.
View Original Abstract

To achieve low-carbon and sustainable development it is imperative to explore water treatment technologies in a carbon-neutral model. Because of its advantages of high efficiency, low consumption, and no secondary pollution, electrocatalytic oxidation technology has attracted increasing attention in tackling the challenges of organic wastewater treatment. The performance of an electrocatalytic oxidation system depends mainly on the properties of electrodes materials. Compared with the instability of graphite electrodes, the high expenditure of noble metal electrodes and boron-doped diamond electrodes, and the hidden dangers of titanium-based metal oxide electrodes, a titanium sub-oxide material has been characterized as an ideal choice of anode material due to its unique crystal and electronic structure, including high conductivity, decent catalytic activity, intense physical and chemical stability, corrosion resistance, low cost, and long service life, etc. This paper systematically reviews the electrode preparation technology of Magnéli phase titanium sub-oxide and its research progress in the electrochemical advanced oxidation treatment of organic wastewater in recent years, with technical difficulties highlighted. Future research directions are further proposed in process optimization, material modification, and application expansion. It is worth noting that Magnéli phase titanium sub-oxides have played very important roles in organic degradation. There is no doubt that titanium sub-oxides will become indispensable materials in the future.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2017 - Electrochemical advanced oxidation processes: A review on their application to synthetic and real wastewaters [Crossref]
  2. 2001 - Electrochemical oxidation of phenol at boron-doped diamond electrode [Crossref]
  3. 2020 - Pulsed electrochemical oxidation of acid Red G and crystal violet by PbO2 anode [Crossref]
  4. 2022 - Magnetically assembled electrodes based on Pt, RuO2-IrO2-TiO2 and Sb-SnO2 for electrochemical oxidation of wastewater featured by fluctuant Cl− concentration [Crossref]
  5. 2006 - Treatment of potato chips manufacturing wastewater by electrocoagulation [Crossref]
  6. 2021 - Moving-bed biofilm reactor combined with three-dimensional electrochemical pretreatment (MBBR-3DE) for 2,4-D herbicide treatment: Application for real wastewater, improvement of biodegradability [Crossref]
  7. 2006 - Electrochemical oxidation of organic pollutants for the wastewater treatment: Direct and indirect processes [Crossref]
  8. 2021 - Electrochemical oxidation of acid orange 74 using Ru, IrO2, PbO2, and boron doped diamond anodes: Direct and indirect oxidation [Crossref]
  9. 1985 - Anodic oxidation of aniline for waste water treatment [Crossref]
  10. 2017 - Performance of nitrogen-doped graphene aerogel particle electrodes for electro-catalytic oxidation of simulated Bisphenol A wastewaters [Crossref]

Reads Similar to This

Advanced hybrid electro-oxidation & O3 technology for water reuse in the fruit and vegetable process industry Efficient spin-photon interface for solid-state-based spin systems for quantum information processing and enhanced metrology Treatment of Municipal Landfill Leachate by Electrochemical Oxidation - Assessing Operating Variables and Oxidation Products