Preparation, characterization of metal oxide and Silicon based nanostructures for energy applications of catalysis, supercapacitors and battery

Abstract

The metal oxides/composite nanostructures (MnO2, rGO/MnO2, NiO, and CuO) have been synthesized via hydrothermally and chemical precipitation process. The prepared metal oxides/composites were characterized by XRD, FTIR, Raman spectroscopy, SEM, EDS, TEM, BET and DRS. The Adsorption and catalytic properties of the catalyst were tested on aqueous solutions containing mono- and multiple dyes, and the optimized process conditions were also established.The results indicate that dye RB-5 exhibits superior removal/degradation percentage using the process of adsorption and Fenton, as compared to the photo catalysis. The removal rates of RB-5 from wastewater treated using MnO2, rGO/MnO2, US/rGO/MnO2, catalyst were 63%, 84%, and 95% respectively, using Fenton/sono-Fenton method. NiO NPs found to be efficient adsorbent for RB5 dye molecules at higher annealing temperature. It is correlated to the band gap and surface area. Also, RB5 adsorption on NiO NPs follows second-order kinetics. CuO NPs were used as a photo catalyst to degrade various dyes, such as methylene blue (MB), acid yellow 23 (AY-23) and reactive black 5 (RB-5), with a low concentration in the presence of visible light. The results show that the highest degradation achieved was 67.8% and 66.3% for RB-5 dye and AY-23 dye, while 43.5% for MB dye from aqueous solution at 5h illumination.The enhanced catalytic performance of metal oxides/composites towards dye removal/degradation is found to be related to its structural and chemical properties. The decomposition products of RB-5 identified using GC–MS technique revealed a higher production rate of fragments in the sono-Fenton process. The kinetics of the reactions were investigated using batch assays. The supercapcitor electrodes fabricated using NWs of MnO2, rGO-MnO2,and Sn@rGO-MnO2 reveal the specific capacitance of 139.05, 309.7 and 460.9 F/grespectively at a scan rate of 20mV/s, in an aqueouselectrolyte Na2SO4 (1 M). The electrochemically prepared silicon nanowires were tested as an anode in Li-ion battery. The charge capacity of the anode is ~3452.47 mAhg-1 at the first cycle with the coulombic efficiency of 85.8 %, and faded to 1134.34 mAhg-1 with coulombic efficiency of 81.6 % after the 12th cycle at a current rate of 1C.