Facile synthesis of NiCo2O4 nanostructures with abundant surface oxygen vacancies, and reduced content of Co and Ni valence states for the efficient and bifunctional electrochemical and photocatalytic oxidation of methylene blue

Abstract

An abundant, low cost, scale up and ecofriendly method has been designed about the preparation of NiCo2O4 nanostructures and the electrode material was employed for the electrochemical oxidation and photocatalytic degradation of methylene blue (MB) under the irradiation of natural sunlight. The NiCo2O4 nanostructures prepared with and without spoiled bitter gourd juice were characterized with respect to morphology, crystalline quality, and surface chemical composition. The morphology of NiCo2O4 nanostructures was transformed from nanorod to low dimension nanoparticles using bitter gourd juice. The surface of NiCo2O4 nanostructures was enriched with the abundant surface oxygen vacancies and low content of different Co and Ni valence states using 10 mL of bitter gourd juice. The NiCo2O4 nanostructures obtained with the 10 mL of bitter gourd were observed highly electroactive towards the oxidation of MB in the phosphate buffer solution of pH 7.4. The linear working range of electrode material for the electrochemical oxidation of MB was estimated from 0.1 mM to 7 mM and a low limit of detection of 0.002 mM was found. A10 mL of bitter gourd juice assisted NiCo2O4 nanostructures were characterized by excellent selectivity, stability and reproducibility. Moreover, the NiCo2O4 nanostructures synthesized with the use of 10 mL of bitter gourd extract were also found active to degrade the MB in aqueous solution under the illumination of natural sunlight. The percent removal of MB was found almost 100 % for the time period of 210 min using NiCo2O4 nanostructures. The phytochemicals from spoiled bitter gourd juice has shown high potential to enhance the electrochemical and photocatalytic properties of NiCo2O4 nanostructures, thus it could be used for the preparation of new generation of electrode materials for the diverse applications.