Simultaneous morphology, band structure, and defect optimization of graphitic carbon nitride microsphere by the precurso
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ARTICLE Simultaneous morphology, band structure, and defect optimization of graphitic carbon nitride microsphere by the precursor concentration to boost photocatalytic activity Shuaijun Wang, Fengting He, Pei Dong, Zhaoxin Tai, Chaocheng Zhao,a) Yongqiang Wang, and Fang Liu State Key Laboratory of Petroleum Pollution Control, China University of Petroleum (East China), Qingdao 266580, People’s Republic of China
Lin Li College of Chemical and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266590, People’s Republic of China (Received 2 July 2018; accepted 5 September 2018)
Graphitic carbon nitride (g-C3N4) microspheres (CNMS) were fabricated via a solvothermal method by using dicyandiamide and cyanuric chloride as precursors. The morphology, band structure, and defects can be simultaneously regulated by merely adjusting the concentration of precursors. Structural characterization results indicate that all the prepared samples possess spherical morphology, while the band gap decreased as the precursor concentration increased from 8 mmol (CNMS-1) to 24 mmol (CNMS-3). Besides, ultraviolet photoelectron spectroscopy results suggested that the valence band of CNMS-2 (16 mmol) was much higher than that of CNMS-1 and CNMS-3. Additionally, organic elemental analysis, X-ray photoelectron spectroscopy, and electron paramagnetic resonance results unveil the formation of nitrogen defects on the surface of prepared samples. Besides, CNMS-2 exhibits an enhanced apparent reaction rate constant of RhB degradation than that of CNMS-1 and CNMS-3. The improved apparent reaction rate constant may be due to the lowered valence band as well as the formation of nitrogen defects. This work might guide the regulation of the morphology and band structure of g-C3N4-based materials prepared via the one-pot hydrothermal method.
I. INTRODUCTION
In the past decades, the energy and environmental crisis have received growing public awareness. To address these problems, semiconductor-based photocatalysis has been used as one of the sustainable approaches owing to its outstanding performances in the H2 evolution from water, CO2 photoreduction, and decomposition of organic pollutants.1–7 The landmark of photocatalytic water splitting using TiO2 electrodes under ultraviolet (UV) light was ignited by Fujishima and Honda in 1972.8 Unfortunately, the traditional TiO2 remains the bottlenecks such as the fast recombination rate of the photogenerated electron–hole pairs and the restricted UV-light response (only about 4% of total sunlight).9,10 To improve the photocatalytic efficiency, Kako and coworkers used Fe and Ta elements to modify TiO2 for organic degradation.11 However, the redox ability is retarded due to the narrowed band gap. Bismuth vanadate (BiVO4) has been an ideal visible light driven semiconductor with a narrow band gap energy of a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2018.342 J. Mater. Res., 2018
2.4 eV (k , 520 nm).12 Wei et al. fabricated BiVO4 hier
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