Biological treatment as a green approach for enhancing electrochemical performance of wood derived carbon based supercapacitor electrodes

Wood-derived biochar is an eco-friendly and porous carbon material that can be used to prepare supercapacitor electrodes. For the purpose of addressing the deficiencies in the specific surface area and pore structure of wood-derived carbon as the raw material of electrodes, a biological pre-treatment method was developed to construct the desirable pore structure of wood by leveraging the lignin-degrading property of white-rot fungi. First, white-rot fungi with permeability and biodegradability on lignocellulosic substrates were used to regulate the pore structure of natural paulownia wood, which was then carbonized to produce a porous hyphae/wood-derived carbon conductive substrate. Afterward, manganese dioxide (MnO2) was deposited on the substrate to fabricate the MnO2/hyphae/wood-derived carbon (HWC-3M) electrode by the hydrothermal method. The degradation of lignin by white-rot fungi broke the original pore structure of wood, strengthened effective channels in the cell walls, and facilitated the loading of MnO2 into the channels to improve the ion transport rate. The HWC-3M had richer energy storage sites, more electrolyte ion transport channels, and better electrochemical performance than the control electrode made of untreated wood-derived carbon (HWC-0), showing an excellent areal specific capacitance (3395 mF/cm2 at a current density of 1.0 mA/cm2), moderate gravimetric specific capacitance (138.3 F/g), and good cycling stability (retention of 88.6% after 2000 cycles). The results indicate that pretreating wood-derived carbon composite electrode with white-rot fungi serves as a new green approach to develop high-performance electrochemical energy storage devices.