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

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 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.