Nano-structural tailoring of manganese dioxide by using pulse current electrodeposition

Abstract

A pulse current technique has been applied for the preparation of Manganese Dioxides (PCMD) in an additive-free MnSO4–H2SO4 solution. The influence of pulse current parameters on surface characteristics has been studied by using scanning electron microscopy (SEM). Pore size distribution (PSD) of samples is determined from the desorption isotherm according to the Barrett–Joyner–Halenda (BJH) model. The subsequent effects on charge discharge cycle performance of deposited materials have been studied in laboratory designed RAM batteries. SEM images confirmed a decrease in PCMDs surface roughness showing more coherent and cracks-free deposits compares to a sample, which is deposited by direct current (DCMD). Results show that under optimized pulse condition, PSD data in PCMD is narrower and less than 3 nm, whereas DCMD exhibits a boarder pore size distribution and larger pore volume. Grain size, pore size distribution and pore volume were established to be important factors determining electrochemical behavior of deposited materials. Results of RAM batteries revealed that the cycle life of batteries made of PCMDs were rather higher than that made by conventional DCMD. Functional improvements are mainly attributed to enhanced current distribution as well as fewer amounts of incorporated water molecules into the PCMD crystal lattice. These could be considered as a result of lower accumulation of passive intermediates and a lower anodic overvoltage during electrodeposition of PCMD. Depending on the applied pulse parameters, nano-tailoring of PCMDs in different morphological varieties is possible.