ZnO/f-MWCNT as a potential candidate for supercapacitive energy storage and piezoelectric energy generation

Abstract

Zinc oxide/ functionalized multiwalled carbon nanotube (ZnO/f-MWCNT) composite was synthesized in two simple steps. In the first step, MWCNT was functionalized using acid refluxing method and in the second step, ZnO/f-MWCNT composite was synthesized in situ via hydrothermal route. Next, possibility of the ZnO/f-MWCNT composite as a hybrid energy storage device was explored through detailed electrochemical and other required investigations. Aiming to real-life applications, a symmetric supercapacitor device was also fabricated followed by detailed performance evaluation. In the last part, energy harvesting possibilities of the ZnO/f-MWCNT composite through the fabrication of a piezoelectric nanogenerator (PENG) was also explored. To do so, ZnO/f-MWCNT/ polyvinylidene fluoride (PVDF) composite films with varying wt% of the filler (i.e. ZnO/f-MWCNT) were prepared. The structural, morphological, compositional, electrochemical and electrical attributes of both the materials were thoroughly investigated. Highest specific capacitance obtained from this ZnO/f-MWCNT electrode was 794 F/g (at 1 A/g) with a power density of 4152 W/kg (at 50 A/g). The PENG device yielded an open circuit voltage of ∼80 V with a power density of 72 kW/m3.