Study of photocatalytic degradation efficiency of rGO/ZnO nano-photocatalyst and their performance analysis using scanning Kelvin probe.

In this work, an efficient reduced graphene-oxide/zinc-oxide (rGO/ZnO) nano-photocatalyst was synthesized via an eco-friendly hydrothermal method to degrade organic dye under visible light exposure and analyzed with Scanning Kelvin Probe (SKP). Prepared samples were characterized via X-ray diffraction (XRD), Field emission-scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform-infrared spectroscopy (FTIR), and UV-Visible absorption spectrophotometer. Structural, morphological, and topological studies revealed the crystal growth of ZnO nanoparticles on rGO as evidenced from XRD, FESEM, and TEM images. UV-Vis studies show the decrease in bandgap energy of rGO/ZnO after the heterostructure formation. UV results confirm the enhanced photodegradation of RhB aqueous solution under visible light. The work function (ɸ) of rGO, ZnO, rGO/ZnO is determined in dark and light conditions by using Scanning Kelvin probe microscopy and discussing their contribution to the photocatalytic process. The novelty of this work is the SKP technique which was used to analyze the degradation mechanism of RhB in the presence of rGO/ZnO catalyst. It is a new way to find out the carrier transport mechanism at the surface of materials with the recorded work function mapping. Photocatalytic activity of rGO/ZnO has shown the maximum degradation of 97% for RhB (pH 7). Our results indicate that more electrons have moved at the catalyst surface and reacted with organic impurities due to larger surface area, which is responsible for suppressing the recombination of photo-induced carriers. [Display omitted] • Facile synthesis and photocatalytic activities of nanostructured rGO/ZnO photocatalyst were investigated. • Exfoliated few-layer rGO nanosheets were obtained with the help of a probe sonicator. • The bandgap of rGO/ZnO nanocomposite was decreased after coupling of rGO nanosheets. • Surface electronic properties and work function were determined by scanning Kelvin probe (SKP) spectroscopy. • rGO/ZnO nanocomposite has shown an enhanced photocatalytic activity with degradation efficiency (97%) for Rhodamine B dye. [ABSTRACT FROM AUTHOR]