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Mechanism-Guided Design of a PPy-TiO2-CNT Nanocomposite for Visible-Light Photodegradation
Al-Ali Hussein1, Soon Huat Tan1, Vel Murugan Vadivelu1
1School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Pulau Pinang, Malaysia.
ACS Omega
|June 29, 2026
Summary
A novel polypyrrole-titanium dioxide-carbon nanotube (PPy-TiO2-CNT) heterojunction efficiently degrades dyes under visible light. This PPy-TiO2-CNT nanocomposite overcomes recombination and transport limitations, achieving high dye removal and durability.
Area of Science:
- Materials Science
- Environmental Chemistry
- Nanotechnology
Background:
- Visible-light photocatalysis for dye degradation faces challenges like limited light absorption, rapid electron-hole recombination, and poor charge transport.
- Existing PPy-oxide or PPy/CNT systems show limitations in interfacial coupling and overall efficiency.
Purpose of the Study:
- To design and synthesize a ternary polypyrrole-titanium dioxide-carbon nanotube (PPy-TiO2-CNT) heterojunction to overcome bottlenecks in visible-light dye photodegradation.
- To investigate the structure-property relationships and optimize operating conditions for enhanced photocatalytic activity and stability.
Main Methods:
- Fabrication of a continuously coupled PPy-TiO2-CNT heterojunction nanocomposite.
- Characterization using DRS/Tauc for optical gap, PL spectroscopy for recombination, and electrochemical impedance spectroscopy (EIS) for charge transfer.
- Photocatalytic degradation experiments with methylene blue (MB) under visible light, optimizing parameters like pH, catalyst loading, and initial dye concentration.
- LC-MS analysis to elucidate the degradation pathway and identify reactive oxygen species (ROS).
Main Results:
- The PPy-TiO2-CNT nanocomposite exhibited an apparent optical gap of ~2.10 eV, enhancing visible light absorption.
- Strong photoluminescence quenching and the smallest Nyquist semicircle indicated suppressed recombination and accelerated interfacial charge transfer.
- Under optimal conditions, 99.4% MB removal was achieved with a rate constant of 0.053 min⁻¹, and 92.3% activity was retained after five cycles.
- LC-MS confirmed a degradation pathway involving ROS, leading to MB mineralization.
Conclusions:
- The ternary PPy-TiO2-CNT heterojunction effectively mitigates recombination and transport limitations, significantly improving visible-light photocatalytic performance.
- The integrated design provides a stable, efficient, and durable system for dye photodegradation.
- This work establishes a mechanism-guided approach for designing advanced photocatalysts for environmental remediation.
