Molten Salts CO2 Transformation: Lower Energy Input and High-Yield Carbon Nanotubes Production Induced by Zinc Oxide

Molten salt electrochemistry is cited as one of the most efficient ways to convert stable but unwanted CO2 into value-added chemical fuels and functional materials, in particular carbon nanotubes (CNTs). In this work, we report the high yield and scalable CO2-deriving CNTs by adding ZnO to molten carbonate electrolyte. The physicochemical properties such as crystal structure, morphology and element composition of the carbon products were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive spectroscopy (EDS), X-ray diffractometer (XRD) and Raman spectrometer (Raman). It is demonstrated that an appropriate amount of ZnO additives can greatly increase the content of CNTs in carbon products. However, the micromorphology and microstructure of the carbon products are found to be significantly changed when the ZnO content is insufficient or excessive. Compared with molten salt electrolyte without ZnO, ZnO-included electrolyte endows CNTs with a higher degree of graphitization and crystallinity. This work demonstrates the feasibility of improving CNTs content in carbon products and lowering required energy for CNTs production by adding ZnO as a promoter.