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

Abstract

The present work is focussed on the 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 has been 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 shows improved structural, morphological and photoelectrochemical properties compared to bare materials. The composite exhibits enhanced visible light absorption with an optimized band gap of 2.59 eV and relatively lower electron-hole recombination. GO/PIn exhibits a 2.3-fold and 1.6-fold increase in photon-to-current efficiency compared to pure PIn and GO. 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 mimics wastewater conditions were performed under the visible/solar light conditions, which is rarely reported in literature. The GO/PIn nanocomposite maintains high photostability and shows consistent photocatalytic efficiency up to eight consecutive cycles which proves its reusability. A detailed mechanistic scheme has been proposed investigating the synergistic photocatalytic effect of GO and PIn in the GO/PIn nanocomposite, making it a promising and sustainable photocatalyst material for real world applications.