Comparative investigation of the catalytic application of α/β/γ-MnO₂ nanoparticles synthesized by green and chemical approaches

ABSTRACT

Three phases (α, β, and γ) of manganese dioxide (MnO₂) are successfully stabilized in a single entity for the first time. For this purpose, Citrullus colocynthis (bitter apple) extract is used as a natural surfactant in green synthesis. MnO₂ nanoparticles were synthesized in the presence and absence of plant extracts under the same conditions. The morphology of both products is analysed by SEM and STEM to understand the role of plant extract in controlling the morphology of particles. The crystallinity and composition are analysed by XRD and confirmed that the product is composed of multiple phases α, β, and γ. The reduction of dyes and nitroarenes is studied using MnO₂ nanoparticles (green and chemical products) as catalysts. The apparent rate constant, a percentage reduction, time reduction and reduced concentration compare the activities of both catalysts. After comparative data analysis, the catalytic reduction of picric acid is found fastest among all the substrates. All the results are analysed based on structure, functional group and affinity towards catalysts.

GRAPHICAL ABSTRACT

KEYWORDS:

• Green
• bitter apple
• chemical
• MnO₂
• catalysis

Acknowledgements

This work is supported by Community College, Post Agriculture Research Station, University of Agriculture, Faisalabad, Pakistan.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The authors confirm that the data supporting the findings of this study are present within the article and its supplementary information. Raw data that support the findings of this study are available from the corresponding author upon reasonable request.