Targeted synthesis and reaction mechanism discussion of Mo2C based insertion-type electrodes for advanced pseudocapacitors
Mo2C is one of the few compounds that possess good electronic conductivity. Meanwhile, it possesses nature 1D zigzag tunnel structure that is ideally suited for fast ion diffusion. Here, an effective approach is demonstrated for fabrication of structurally stable N-doped Mo2C/C nanobelts. It demonstrates high and fast energy storage ability with initial capacitances of 1,139 C g−1 at 1 mV s−1, 151 C g−1 at an extremely high scan rate of 2,000 mV s−1 and 208 C g−1 at a discharge current density of 200 A g−1. After electrochemical activation of cycling, the capacity is continuously enhanced and much higher capacitances of 2,523 C g−1 at 1 mV s−1 and 1,403 C g−1 at 50 A g−1 are achieved after 15,000 cycles’ cycling at 50 mV s−1. Using power law, surface-controlled capacitive process is evaluated and it is over 90% when the scan rates are higher than 10 mV s−1 and still high as 73% at 1 mV s−1. From in-situ synchrotron XRD, it is found that there is negligible crystal structure and volume change during charging/discharging, reflecting an insertion-type charge storage mechanism.