Facile synthesis and electrochemical characterization of erbium oxide and hydroxide for supercapacitor applications

Novel Er-based electrodes including Er(OH)₃ or Er₂O₃ material were introduced and synthesized via facile steps to present novel supercapacitor electrodes. Herein, the hexagonal Er(OH)₃ crystals were designed as small particles having a micro size in their diameters and nano size in their width. Additionally, the cubic Er₂O₃ material was prepared as a clear nanoscale-size particle. The difference in the morphology in both Er-oxide and hydroxide could be due to the preparation strategy which uses traditional calcination to prepare Er₂O₃ and the hydrothermal strategy for Er(OH)₃. Interestingly, around 55% of the Er-oxide particles have around 14 nm, and others have a size from 3 to 22 nm. After that, the designed Er(OH)₃ or Er₂O₃ materials were targeted as working electrodes for supercapacitor usage. Cyclic voltammetry, charge-discharge, and impedance analysis were used for such investigations. The specific capacitance (C_s) data of the Er₂O₃ electrode show better capacitance characteristics if compared with Er(OH)₃ electrode. At 5 mV/s, the C_s were found at 822.99 F/g and 783.42 F/g for Er₂O₃ and Er(OH)₃ electrodes, respectively. This enhancement was observed at low scan rates such as 0.005 V/s and high scan rates (0.08 V/s). This behavior could be due to the superior characteristics and morphology of Er₂O₃ material to what is found in the case of Er(OH)₃.