Synergistic effect of heat treatments and KOH activation enhances the electrochemistry performance of polypyrrole nanochains (PPy-NCs)

A highly intriguing class of advanced materials, nanochains have gained attention due to their advantages in stability, enlarged surface area and enhanced electrocatalytic activity toward oxygen reduction reaction (ORR). Here in, we describe the synthesis of polypyrrole nanochains (PPy-NCs) by a facile emulsion polymerization process using cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulphate (SDS) as surfactants. The PPy-NCs are further activated using potassium hydroxide (KOH) as the activation agent for producing a porous nitrogen-containing carbon structure. Subsequently, low-temperature carbonization (500-800 °C) and KOH activation leads to abundant ultrasmall pores and strong oxygen molecule binding sites, which are essential in enhancing the capacitance as well as ORR activity. The morphologies and structures of the PPy-NCs samples have been characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and Brunauer-Emmett-Teller (BET). The electrochemical studies were analyzed by cyclic voltammetry, galvanostatic charge/discharge measurements, and electrochemical impedance spectroscopy, which demonstrate superior electrochemical performance as supercapacitors electrode application. The maximum specific capacitance of 1502 F g−1 at scan rate 2 mV s−1, as well as capacitance retention (93%) after completing 1500 cycles are obtained for the PPy-NCs-800 electrode in 1.0 M KOH aqueous solution. Moreover, PPy-NCs-800 exhibits a considerably good electrocatalytical activity through desirable 4-electron transfer process for ORR in alkaline medium. This work suggested that PPy-NCs had potential application in supercapacitors, and oxygen reduction reaction (ORR).