A novel WO2@FeWO4 composite derived from polyoxometalates@Fe–metal–organic frameworks and its electrochemical properties
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In this paper, we synthesize a needle-like polyoxometalates@Fe-based metal–organic framework (POM@Fe–MOFs) composites, in which the Keggin-type W-based POM with negative charges exist as secondary building units of Fe-based MOFs. Based on the synthesized POM@Fe–MOFs, WO2@FeWO4 is easily prepared by appropriate thermal treatment. On the one hand, the derivative retains the original POM@Fe–MOFs morphology. Owing to the face that the Fe element contains variable valence state and the W element in tungstophosphoric acid exists in the form of high valence, both of which have great potential in the field of electrochemistry. According to the systematical characterization, the results show that WO2@FeWO4 composite can be used as positive electrodes in supercapacitors which is reported for the first time. In addition, the WO2@FeWO4 is confirmed to exhibit an excellent capacity of 124 F g−1 at a current density of 0.5 A g−1 in 6 M KOH when used in supercapacitors, which can be attributed to the redox reaction of W element.
This work was financially supported by the National Natural Science Foundation of China (61604110), China Postdoctoral Science Foundation (2015M572210, 2016M602376), Natural Science Foundation of Hubei Provincial, China (2018CFC796, 2017CFC829, 2017CFB291), Department of Education Science Research Program of Hubei Province (Q20161110), and Open Foundation of Key Laboratory of Green Chemical Process (Wuhan Institute of Technology), Ministry of Education (NRGCT201503), Training Programs of Innovation and Entrepreneurship for Undergraduates of Province (201510488022), Guidance project of scientific research plan of Hubei Provincial Department of Education (B2017014), Key Projects of Scientific Research Program of Hubei Provincial Department of Education (D20171505).
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