Highly efficient catalytic reduction and electrochemical sensing of hazardous 4-nitrophenol using chitosan/rGO/palladium nanocomposite

Abstract

Designing and developing new catalytic materials is important in industrial and practical applications. Polysaccharide supported nanocomposites have gained increased attention due to the urgent need of non-toxic, environmental friendly and highly effective catalyst. Novel cross linked chitosan/rGO/palladium nanocomposites with different weight percentages of graphene and palladium were synthesized via simple and cost effective chemical reduction method. Electrostatic interaction between opposite charged groups of chitosan and palladium was analysed using FTIR and Raman spectroscopy. A mechanism for incorporation of palladium into the chitosan supported reduced graphene oxide (rGO) is proposed. Further, chitosan/rGO/palladium nanocomposites were characterized using FESEM and HRTEM. Size of the palladium nanoparticles was assessed to be 2–3 nm. XRD pattern confirms the presence of chitosan, graphene and (111) orientated Pd nanoparticles. Optical property of composites containing different weight percentages of rGO and Pd was analyzed using UV–Vis spectroscopy. Catalytic activity of nanocomposites, CS/rGO/Pd-5%, CS/rGO/Pd-10% and CS/rGO/Pd-15% was studied using 4-nitrophenol (4-NP) as the model reactant. Turn over frequency (TOF) of the catalyst, CS/rGO/Pd-15% was calculated to be 19.8 h⁻¹. Concentration (wt% of) dependent catalytic behavior was observed. Chitosan/rGO/palladium nanocomposites modified glassy carbon electrode (GCE) was fabricated for the electrochemical determination of 4-nitrophenol using cyclic voltammetry. Limit of detection was found to be 86 nM. Sensitivity of the electrode was found to be 0.06875 μA μM⁻¹ cm⁻². It is concluded that the performance of this catalyst is an alternative technique for the sensing of 4-nitrophenol and catalytic hydrogenation to remove the toxic pollutants.