Solar-driven Pt free hydrogen production and successive degradation of sulfasalazine using CuO/ZnO binary nanocomposites: Reaction kinetics and determination of reaction parameters using response surface methodology

Abstract

Background

Approaches for sustainable, green, and expensive catalyst-free hydrogen production have not been explored extensively. Moreover, during photocatalysis, a lot of material gets wasted due to a lack of proper optimization of the reaction parameters to remove the toxic industrial effluents.

Methods

Here in this study, we present the green synthesis of CuO/ZnO nanocomposites from the ethanolic crude extract of Oxystelma esculentum. The synthesized photocomposites were systematically characterized by Fourier transform infrared spectroscopy, zeta potential, x-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and x-ray photoelectron spectroscopy. The performed analyses provided useful insights into identifying important functional groups, size, morphology, elemental composition, crystallinity, and defects in the synthesized photocomposites.

Significant Findings

After characterization, the nanocomposites were evaluated for photocatalytic sulfasalazine (SSZ) degradation and hydrogen production. The response surface methodology (RSM) was employed to optimize SSZ's photocatalytic degradation. The optimized values of reaction parameters for the photocatalytic degradation of SSZ comprise pH = 4.06, SSZ dose = 47.75 mg/L, CuO/ZnO dose = 44.42 mg, and temperature = 23.60 °C. The rates observed in the hydrogen production (1136 µmolh^-1g^-1) were obtained without costly co-catalyst. The optimized values for hydrogen production include photocatalyst dosage = 50 mg, pH = 7, and time = 5 hours. These features signify the efficient separation of charge carriers between synthesized nanocomposites, resulting in exquisite activities.