Enhanced photocatalytic performance of ZnO under visible light by co-doping of Ta and C using hydrothermal method.

This study attempted to improve the photocatalytic activity of zinc oxide (ZnO) semiconductors in the visible light region by introducing the co-doping of carbon (C) and tantalum (Ta) to ZnO (ZTC) using a simple hydrothermal method with the respective precursors. The obtained uniform ZTC nanoparticles with an average crystal size of 29.30 nm (according to Scherrer's equation) revealed a redshift with a decrease in bandgap (Eg) from 3.04 eV to 2.88 eV, allowing the obtained photocatalyst to absorb the energy of the visible light for photocatalysis. Furthermore, the Zn 2p and Ta 4f core level spectra confirmed the presence of Zn2+ and Ta5+ in the ZTC sample. In addition, the infrared spectra identified hydrogen-related defects (HRDs), while the O 1s spectra indicated the existence of oxygen vacancies (VO). Electrochemical tests revealed improvement in the electron conductivity and charge separation of the obtained materials. To follow, the photocatalytic performance assessment was conducted by varying the C/Zn2+ ratios (5, 10, and 15 mol%) in ZTC samples, the initial RhB concentration (7, 15, and 30 ppm), and the pH of the RhB solution (3.0-10.0). The photodegradation on ZTC samples showed the most effectiveness for a 7 ppm RhB solution with a C/Zn2+ ratio of 10 mol% in the slightly alkaline medium (pH 9.0). Additionally, ZTC also exhibited commendable durability after being reused several times. The nature of RhB photodegradation was proposed and discussed via a mechanism at the end of this work.

A comparative study of 0D and 1D Ce-ZnO nanocatalysts in photocatalytic decomposition of organic pollutants.

Nanosized zinc oxide is an intriguing material that can be applied in various fields. In this study, Ce doped ZnO nano-catalysts (Ce-ZnO) were synthesized by two different methods (i.e., hydrothermal (Ce-ZnO-HT) and polymer gel combustion (Ce-ZnO-CB) methods) to compare their photodegradation efficiency. The prepared material characteristics were investigated using XRD, SEM, TEM, FTIR, UV-Vis, PL, XPS, EDS, and BET. The bandgap of both nanoparticles (NPs) was 2.95 eV, despite the fact that the morphology of Ce-ZnO-HT NPs was 1D-rod-shaped and that of Ce-ZnO-CB NPs was 0D-spherical. However, the surface area and oxygen vacancy rate of Ce-ZnO-HT NPs were higher than those of Ce-ZnO-CB NPs. These differences are directly related to the photocatalytic activity of Ce-ZnO NPs. Accordingly, the results showed that photocatalytic efficiency was classified in the order Ce-ZnO-HT > Ce-ZnO-CB > pure ZnO, and the photocatalytic reaction rate constant of Ce-ZnO-HT used to decompose MB was 3.0 times higher than that of Ce-ZnO-CB. Interestingly, the photodegradation mechanism study revealed that hydroxyl radicals and holes were shown to be more important contributors to methyl blue degradation than photo-induced electrons and superoxide radical ions.