EFFECT OF PULSE CURRENT ON MORPHOLOGY AND CRYSTAL STRUCTURE OF ELECTROLYTIC MANGANESE DIOXIDE

• Main Author: SABILLA ROSYAD (NIM : 12514065), SAFIRA
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/30765
• Institution: Institut Teknologi Bandung

Main primary source to produce manganese metal and compounds is pyrolusite mineral. High grade ores (i.e. Mn content >40%) is commonly treated by using pyrometallurgical route to produce ferromanganese (FeMn) and sillicomanganese (SiMn) alloys. Meanwhile, low grade ores is usually processed through hydrometallurgical route which involves leaching, pregnant leach solution purification and electrolysis or chemical precipitation to produce electrolytic manganese dioxide (EMD) and other manganese compounds. EMD characteristic is dependent on electrolysis conditions. As battery and supercapacitor component, good electrochemical activity of EMD is required. This characteristic is a function of morphology and crystal structure of the deposit. Several publications report that the EMD produced by direct current electrolysis has not provided a maximum discharge capacity and cycle performance of the battery. Pulse current electrolysis is one of the methods which is considered to be able to improve the morphology and crystal structure of EMD for obtaining a better electrochemical activity. In this research, the effect of pulse current on morphology and crystal structure of EMD is studied. <br /> <br /> The electrolyte solution was prepared by dissolving 50.37 g MnSO4.H2O in 500mL H2SO4 of 0.5M for obtaining dissolved Mn concentration of 0,2 M. A series of electrolysis experiment was carried out by using titanium anode and carbon as cathode for 4 hours. Direct current electrolysis experiments were performed under variations of current density and temperature, meanwhile in the pulse current electrolysis experiment duty cycle and pulse frequency were varied. Every one hour during electrolysis tests, current and cell voltage were measured periodically using ampere meter and voltmeter, respectively. After electrolysis experiment was finished, EMD deposit is analyzed by Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) to determine its morphology, crystal structure and grain size and the characteristics of EMD produced by DC current and pulse current are compared. <br /> <br /> The result of direct current electrolysis experiments shows that higher current density (i.e. 2 A/dm2) resulted in lowering of current efficiency but producing finer particle size. The increased of temperature from 80 to 95oC tend to increase particle size of the deposit. For pulse current electrolysis, increasing duty cycle and frequency resulted in finer particle size. Although both direct current and pulse current electrolysis resulted in similar crystal structure (i.e. &#61543; and &#61541;-MnO2), pulse current electrolysis tends to generate a better crystallinity of EMD deposit. Moreover, pulse current electrolysis produces also a finer grain size than direct current one.