Structure–Property–Composition Relationships in Doped Zinc Oxides: Enhanced Photocatalytic Activity with Rare Earth Dopants

Abstract

In this paper, we demonstrate the use of continuous hydrothermal flow synthesis (CHFS) technology to rapidly produce a library of 56 crystalline (doped) zinc oxide nanopowders and two undoped samples, each with different particle properties. Each sample was produced in series from the mixing of an aqueous stream of basic zinc nitrate (and dopant ion or modifier) solution with a flow of superheated water (at 450 °C and 24.1 MPa), whereupon a crystalline nanoparticle slurry was rapidly formed. Each composition was collected in series, cleaned, freeze-dried, and then characterized using analytical methods, including powder X-ray diffraction, transmission electron microscopy, Brunauer-Emmett-Teller surface area measurement, X-ray photoelectron spectroscopy, and UV-vis spectrophotometry. Photocatalytic activity of the samples toward the decolorization of methylene blue dye was assessed, and the results revealed that transition metal dopants tended to reduce the photoactivity while rare earth ions, in general, increased the photocatalytic activity. In general, low dopant concentrations were more beneficial to having greater photodecolorization in all cases.

Structural, Electrical, and Optical Effects of Metal Doping on ZnO Thin Films

“…Valence band (VB) and conduction band (CB) levels, and the corresponding band gaps of ZnO and oxides of the respective dopants …”

“…Doping ZnO with Al (AZO) including its electrochemical texturing, [3][4] W (WZO), [5] Mn (MZO), [6] Ti, [7] and many other elements was done with satisfactory results, and even rare earth dopants were analyzed. [8] The aim of this study was to perform a qualitative comparison between different doping candidates. Ti, W, Zr, and Mn were chosen as dopants due to good results presented in previous studies as mentioned before.…”

Synthesis of magnetically separable Fe3O4@PANI/TiO2 photocatalyst with fast charge migration for photodegradation of EDTA under visible-light irradiation

“…Photocatalysis technique is considered to be one of the most effective methods to resolve aforementioned problems [7][8][9]. In recent years, the exploitation of novel photocatalyst with superior visible-light response is a very hot research area [10][11][12][13][14].…”

Facile synthesis, characterization, and decolorization activity of Mn2+ and Al3+ co‐doped hexagonal‐like ZnO nanostructures as photocatalysts

“…In addition, approximately 40% of the sunlight is the visible radiation, while only about 8% of it is the ultraviolet radiation . For reducing the band gap to the visible light region, various metallic ions such as copper, nickel, cobalt, manganese, or aluminum are doped to the structural network of zinc oxide …”