Pure and cerium‐doped zinc oxides: Hydrothermal synthesis and photocatalytic degradation of methylene blue under visible light irradiation

Abstract

Pristine and cerium-doped zinc oxides with a different dopant concentration between 1 and 5% were fabricated using the hydrothermal method. Prepared materials show direct bandgaps of comparable values. Cerium-doped materials show UV-Vis spectra with broad tails toward the visible light range. Pure zinc oxide displays the flower-like form, while cerium-doped materials possess rod-shaped morphologies. The materials were tested for the degradation performance of methylene blue under visible light irradiation. To elucidate the difference in their performance, further measurements and experiments were conducted. Overall, 3%-cerium doped zinc oxide shows the greatest photocatalytic performance. This is possibly attributed to its rod shape with good uniformity and to the enrichment of oxygen vacancies in its surface layers. Finally, trapping experiments reveal that positive holes and hydroxyl radicals were the predominant active species during the photocatalytic degradation process.

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

“…This ratio was previously reported that have the best photocatalyst performance among the different content of Ce. 25,38 The detailed procedure was described elsewhere. 25 Briey, 1.098 g of Zn(CH 3 COO) 2 $2H 2 O and 0.065 g of Ce(NO 3 ) 3 $6H 2 O were dissolved in 75 ml C 2 H 5 OH.…”

“…25,38 The detailed procedure was described elsewhere. 25 Briey, 1.098 g of Zn(CH 3 COO) 2 $2H 2 O and 0.065 g of Ce(NO 3 ) 3 $6H 2 O were dissolved in 75 ml C 2 H 5 OH. Subsequently, 75 ml of 0.4 M NaOH solution was added slowly and kept stirring for 60 min.…”

“…Particularly, several scavengers such as silver nitrate (AgNO 3 ), EDTA, isopropanol, and 1,4-benzoquinone were employed for capturing photogenerated electrons (e À ), hole (h + ), hydroxyl radicals (cOH), and superoxide radicals (cO 2 À ), respectively. 25,39,40 The deterioration of MB solution was tracked in order to discover active species. In the present study, 1 mM scavengers were added before the initiation of the reaction.…”

“…2,20,22 This is due to the fact that dopants can serve as electron scavengers, preventing the recombination of electrons with holes. 23 The dopant can be metals such as Mn, 24 Ce, [25][26][27] Fe, 28 Ni, 29 La, 27 or non-metal such as C, 30,31 N, 32 P, 33 or a combination of multiple dopants. 18,[34][35][36] Rare-earth (RE) metals (e.g., La, Ce, Eu) have received increased interest due to their unique 4f and 5d electrical structures and spectrum properties.…”

“…The majority of RE-doped materials were found to have superior photocatalyst capabilities than pure ZnO NPs. 25,27,37 However, direct comparison is difficult since each author utilized a different dopant content, synthetic procedure, and concentration of organic compounds. Besides, the material's catalytic mechanism must be explained in order to show the function of radicals generated during the irradiation process.…”