Ex situ structure-properties analysis of CeOx-TiOx-RGO as a potential groundbreaking Na-ion supercapacitor material

F. Caballero-Briones, N. Gnanaseelan, F.J. Espinosa-Faller, J. Mustre, J. Lezama, R.A. Colina-Ruiz
Instituto Politecnico Nacional,

Keywords: Na-ion supercapacitor, graphene oxide, cerium titanate, XANES


A novel CeOx-TiOx-reduced graphene oxide (rGO) composite named as CTG, was prepared by using alkaline treated TiO2 nanoparticles to form alkali-titanate, which was then converted by an hydrothermal treatment to Ce-titanate, which served as the active material from where a Na-ion supercapacitor with high stability and high capacity was build. The material’s study shows Ce2Ti3O9 as the main crystal phase; the nanoparticles are surrounded by rGO sheets. The electrochemical behavior indicated a pseudocapacitance activity attributed to the redox pair Ce4+/Ce3+ and good electrical conductivity attributed to RGO sheets. The Na-ion supercapacitor has an energy density of 15 KWh/kg and a power density of 750 W/kg. The device showed an excellent cyclic behavior for 5000 cycles with >95% retention capacity at 2 Ag-1. An X-ray absorption near edge spectroscopy (XANES) characterization has been conducted on CTG/FTO electrodes, previously cycled in an aqueous Na-based electrolyte at 1 and 10 cycles. The results show evidence of Na-incorporation and a drastic reduction of Ce3+ states after 1 charging cycle, as well as effects of different magnitude on the C, and O edges, while Ti edge is almost unaffected. A restoration of the atomic environment after cycling, that shall be related to the device's stability was observed. The large capacity and the long term stability of the superpacitor suggests CTG as a possible game-changing material for novel storage devices. Work financed by CONACYT-Mexico through the 2019-40798 grant