Scalable synthesis and characterization of free-standing supercapacitor electrode using natural wood as a green substrate to support rod-shaped polyaniline

Abstract

Natural wood slice was used as a green substrate to support rod-shaped polyaniline via a scalable easily-operated immersion–oxidative polymerization–freeze drying pathway. The scanning electron microscopy observations show that the wood surface was densely covered with plentiful polyaniline nanorods with diameters of 31–72 nm and lengths of 240–450 nm. The analysis of Fourier transform infrared spectroscopy provides further evidence of polyaniline coating onto the wood substrate. Moreover, the analysis of X-ray photoelectron spectroscopy indicates a strong hydrogen bonding between the nitrogen lone pairs $(\ddot{\text{N}})$ of polyaniline and the −OH groups of wood, which plays an important role in the interface bonding. This core–shell composite can serve as a free-standing supercapacitor electrode, which shows a high specific capacitance of 304 F g⁻¹ at 0.1 A g⁻¹, a high coulombic efficiency of 93–100 %, and a moderate cyclic stability with a capacitance retention of 72.3 % after 5000 cycles. These make the natural wood a good alternative green substrate to develop novel eco-friendly energy storage devices.