Abstract
Bagasse-derived carbon electrodes were developed by doping with nitrogen functional groups and compositing with high-capacity MnO(2) nanoparticles (MnO(2)/NBGC). The bagasse-derived biochar was N-doped by refluxing in urea, followed by the deposition of MnO(2) nanoparticles onto its porous surface via the hydrothermal reduction of KMnO(4). Different initial KMnO(4) loading concentrations (i.e. 5, 10, 40, and 100 mM) were applied to optimize the composite morphology and the corresponding electrochemical performance. Material characterization confirmed that the carbon composite has a mesoporous structure along with the dispersion of MnO(2) nano-particles on the N-containing carbon surface. It was found that the 5-MnO(2)/NBGC sample exhibited the highest electrochemical performance with a reversible capacity of 760 mA h g(-1) at a current density of 186 mA g(-1). It delivered reversible capacities of 488 and 390 mA h g(-1) in cycle tests at 372 and 744 mA g(-1), respectively, for 150 cycles and presented good reversibility with nearly 100% coulombic efficiency. In addition, it could exert high capacities up to 388 and 301 mA h g(-1) even under high current densities of 1860 and 3720 mA g(-1), respectively. Moreover, most of the prepared composite products showed high rate capability with great reversibility up to more than 90% after testing at a high current density of 3720 mA g(-1). The great electrochemical performance of the MnO(2)/NBGC nanocomposite electrode can be attributed to the synergistic impact of the hierarchical architecture of the MnO(2) nanocrystals deposited on porous carbon and the capacitive effect of the N-containing defects within the carbon material. The nanostructure of the MnO(2) particles deposited on porous carbon limits its large volume change during cycling and promotes good adhesion of MnO(2) nanoparticles with the substrate. Meanwhile, the capacitive effect of the exposed N-functional groups enables fast ionic conduction and reduces interfacial resistance at the electrode interface.