2, Physics, Tulane University, New Orleans, Louisiana, United States
3, Novacentrix, Austin, Texas, United States
Transition metals oxides have attracted attention due to their high pseudocapacitance and excellent performance in electrochemical applications. More recently, the research has focused on fabrication of the mixed transition metal oxides, because of their wide working voltage range, resulting in enhanced specific capacitance. Our research has focused on preparation of manganese-cobalt based mixed oxides (Mn-Co); specifically, we hypothesize that Co addition hinders the dissolution of Mn into the electrolyte, resulting in enhanced capacitance and long cycle-life. By using photonic curing system (PulseForge 1300, Novacentrix, with fluence value of 7.5 J/cm2) for the pulsed Xe light irradiation of spray-coated (Mn-Co)-acetylacetonate solid precursor films under ambient whereby we have instantaneously synthesized films on commercial Pt-coated Si-substrates for potential use as electrode materials in supercapacitor devices. We have shown that the first two pulses of irradiation of (Mn-Co)-acetylacetonate molecules result in self-assembly and crystallization of nanocomposite thin films while subsequent pulses improve the crystallinity of nanocomposite film and evaporate the carbon component. We characterized our films using Scanning Electron Microscopy, X-ray Diffraction, and Raman Spectroscopy. Electrochemical characterization, i.e., cyclic voltammetry and charge-discharge cycling, were carried out in three-electrode cell configuration (where Hg-HgO, Pt, and our sample are the reference, counter and working electrodes respectively) with 1 M KOH as the electrolyte. The presence of redox peaks in cyclic voltammetry curves confirms the pseudocapacitive behavior of the sample while identical CV curves even at higher scan rates further suggest excellent rate capability and ideal supercapacitor behavior. The galvanostatic charge-discharge measurements (GCD) performed at 0.25 mA current resulted in specific capacitance as high as 12 mF/cm2 for the electrode prepared with 2-pulses of irradiation. After performing GCD measurements for 5000 cycles, we found that the electrode retains as high as 80% capacitance, which shows that as prepared electrode possesses excellent stability and long cycle-life. Next steps will be the work on other mixed oxides electrodes, such as Ni-Mn oxides, Mn-Fe oxide and thicknesses and different fluence values during irradiation.