Ce3+-ion, Surface Oxygen Vacancy, and Visible Light-induced Photocatalytic Dye Degradation and Photocapacitive Performance of CeO2-Graphene Nanostructures

Abstract

Cerium oxide nanoparticles (CeO2 NPs) were fabricated and grown on graphene sheets using a facile, low cost hydrothermal approach and subsequently characterized using different standard characterization techniques. X-ray photoelectron spectroscopy and electron paramagnetic resonance revealed the changes in surface states, composition, changes in Ce4+ to Ce3+ ratio, and other defects. Transmission electron microscopy (TEM) and high resolution TEM revealed that the fabricated CeO2 NPs to be spherical with particle size of ~10–12 nm. Combination of defects in CeO2 NPs with optimal amount of two-dimensional graphene sheets had a significant effect on the properties of the resulting hybrid CeO2-Graphene nanostructures, such as improved optical, photocatalytic, and photocapacitive performance. The excellent photocatalytic degradation performances were examined by monitoring their ability to degrade Congo red ~94.5% and methylene blue dye ~98% under visible light irradiation. The photoelectrode performance had a maximum photocapacitance of 177.54 Fg−1 and exhibited regular capacitive behavior. Therefore, the Ce3+-ion, surface-oxygen-vacancies, and defects-induced behavior can be attributed to the suppression of the recombination of photo-generated electron–hole pairs due to the rapid charge transfer between the CeO2 NPs and graphene sheets. These findings will have a profound effect on the use of CeO2-Graphene nanostructures for future energy and environment-related applications.

Microbial fuel cell assisted band gap narrowed TiO2 for visible light-induced photocatalytic activities and power generation

“…Generally, EIS is used to examine the electrochemical properties of the materials; hence, it was performed to understand the charge transfer resistance and charge separation efficiency between the photogenerated electrons and holes in the w -TiO 2 and g -TiO 2 nanoparticles. The charge separation efficiency of photogenerated electrons and holes is a critical factor for the photoelectrode and photocatalytic activities 50 – 52 . Figure 6b shows EIS Nyquist plots of the w -TiO 2 and g -TiO 2 nanoparticles in the dark and under visible light irradiation.…”

“…The arc radius of the EIS spectra reflects the interface layer resistance arising at the electrode surface 50 . A smaller arc radius indicates higher charge transfer efficiency 21 , 50 – 52 . The arc radius of the g -TiO 2 nanoparticles was smaller than that of w -TiO 2 nanoparticles in the dark and under visible light irradiation.…”

Biomass-derived Carbon Quantum Dots for Visible-Light-Induced Photocatalysis and Label-Free Detection of Fe(III) and Ascorbic acid

“…Since the first photocatalytic use of TiO 2 10 , semiconductor photocatalysis has attracted considerable research attention; however, the typically employed hybrid photocatalysts are toxic, less active in the visible region, expensive, or require time-consuming and multi-step synthesis procedures, limiting their practical applications 11–13 . Much effort has been dedicated to developing novel photocatalyst systems to maximize the utilization of visible light 14 . Photocatalytic materials with high photocatalytic performance in the visible region are therefore highly desirable.…”

Steam activation of waste biomass: highly microporous carbon, optimization of bisphenol A, and diuron adsorption by response surface methodology

“…The negative entropy (Δ S °) of BPA and diuron adsorption indicates that randomness is decreased at the solid-liquid interface (Badruddoza et al 2011). Moreover, the adsorption process is supposed to be physisorption, when the values of Δ G ° are between 0 and − 20 kJ/mol, whereas for chemisorption, the values of Δ G ° are generally between − 80 and − 400 kJ/mol (Khan et al 2017; Zbair et al 2018b). In this study, Δ G ° obtained ranged between − 7 to − 17 kJ/mol for BPA and − 10 to − 18 kJ/mol for diuron, which means that the adsorption process of BPA and diuron on ANS@H2O-120 is physisorption.…”