Impact of isopropanol on nucleation and growth of polyaniline nanofibers towards capacitive charge storage enhancement

•Presenting facile flow polymerization for preparing PANI nanofibers;•Achieving large specific capacitance under flow condition;•Further improving the capacitance performance by introducing isopropanol;•Identifying the influences on the nucleation and growth of the nanofibers. The nanofibrous morphology and chain orientation have predominant impacts on the charge storage ability of polyaniline (PANi) that could be promoted by introducing small molecules such as alcohols to affect the formation of the nanofibers. In this work, one kind of continuous–flow polymerization was designed to separate the seed formation and subsequently assembly process of PANi nanofibers, making it possible to evaluate independently the influence of isopropanol on the nucleation and growth of PANi nanofibers, i.e. isopropanol molecules were involving in the initial reaction in the flow polymerization, or only in the subsequent assembly and growth of nanofibrous seeds produced through flow polymerization. Furthermore, the effects of isopropanol content on the morphologies, microstructures and capacitance performances of PANi nanofibers were discussed. It is found that the isopropanol could give a great improvement in charge storage ability of the nanofibers when a small amount of alcohol molecules were only used for affecting the assembly and growth of PANi nanofibers. Benefiting relatively large diameter–to–length ratio and high conductivity, PANi nanofibers prepared at 5 wt. % content of isopropanol possessed the greatest specific capacitance of 1082 F g–1 at the scan rate of 1 mV s–1 and 530.2 F g–1 at the current density of 1 A g–1, which was improved by 10% compared with pure PANi. The understanding of effect of small organic molecules on the capacitance performances of PANi could provide a much easier route in fabricating high performance electrode of PANi as promising candidates for lightweight and flexible energy storage devices.