Graphene oxide/polyindole nanocomposite: a highly efficient multi-cyclic, stable and sustainable photocatalyst platform for wastewater remediation under visible light

Abstract

The present work focuses on visible light-driven photodegradation of anionic and cationic dye mixtures via metal-free and carbon-based multicyclic nanocomposites. In this context, graphene oxide (GO) has demonstrated tremendous potential in recent years as an excellent adsorbent and promising photocatalyst. Furthermore, conducting polymers (CPs) are emerging carbon-based materials with complementary photocatalytic properties. In this study, polyindole (Pln), a CP, was combined with GO to counter its major drawbacks such as hydrophilicity, chemical leaching, recyclability and difficulty in extraction. A series of GO/Pln composite photocatalysts, i.e. GO as x%GO/PIn (x% = 10, 15, 20 and 25), were synthesized via energy-economic in situ chemical oxidative polymerization. The GO/PIn nanocomposite showed improved structural, morphological and photoelectrochemical properties compared to bare materials. The composite exhibited enhanced visible light absorption with an optimized band gap of 2.59 eV and relatively low electron–hole recombination. GO/PIn exhibited 2.3-fold and 1.6-fold increases in photon-to-current efficiency compared to pure PIn and GO, respectively. This work provides an excellent sustainable photocatalyst platform (i.e. GO/PIn heterostructure nanocomposite) for wastewater remediation. The photodegradation of different mixtures of organic dyes that mimic wastewater conditions was performed under visible/solar-light conditions, which is rarely reported in the literature. The GO/PIn nanocomposite maintained high photostability and showed consistent photocatalytic efficiency over eight consecutive cycles, which prove its reusability. A detailed mechanistic scheme investigating the synergistic photocatalytic effect of GO and PIn in the GO/PIn nanocomposite is proposed, making it a promising and sustainable photocatalyst material for real-world applications.