A Sustainable Approach to the Preparation of MoO 2 Quantum Dots and the Pseudocapacitive Performance before and after Calcination

Yi An, Weizhi Gong, Junli Wang, Jianlin Liu, Liexing Zhou, Yi Xia, Cheng Pan, Mingjun Wang and Dong Fang
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Yi An: Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China
Weizhi Gong: Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China
Junli Wang: Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China
Jianlin Liu: Faculty of Science, Shaoyang University, Shaoyang 422000, China
Liexing Zhou: Analytic and Testing Research Center of Yunnan, Kunming 650093, China
Yi Xia: Analytic and Testing Research Center of Yunnan, Kunming 650093, China
Cheng Pan: Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China
Mingjun Wang: Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China
Dong Fang: Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China

Sustainability, 2022, vol. 14, issue 9, 1-10

Abstract: The present preparation methods of molybdenum dioxide (MoO 2 ) quantum dots (QDs) are often cumbersome and not environmentally friendly, and more importantly, the prepared MoO 2 QDs are usually wrapped in surfactants, which are difficult to be removed and impact their intrinsic characterization and performance. Herein, we present a facile, scalable and sustainable approach to obtain clean and pure MoO 2 QDs (1.5~3 nm), which consists of a hydrothermal reaction and a further calcination process in vacuum following freeze drying. Furthermore, the influence of calcination temperature, atmosphere and time is also studied. The calcination at 400 °C for 2 h in vacuum can efficiently remove the surfactants wrapping on the MoO 2 QDs without obvious size change, whereas the calcination in nitrogen will lead to a slight increase in size, and the calcination in air could transform MoO 2 QDs into MoO 3 nanoplates. In addition, the pseudocapacitive performance of the as-prepared samples is tested and compared by electrochemical methods, and the specific capacitance of the clean MoO 2 QDs is about 1.4 times larger than that of MoO 2 QDs with surfactants at 5 mV s −1 . This study also demonstrates a possible way to efficiently remove the organic substance wrapping on quantum dot materials.

Keywords: MoO 2 quantum dots; surfactants; calcination; MoO 3; intercalation pseudocapacitance (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2022
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