Abstract
In this work, a three-dimensional porous mycelium-derived activated carbon (3D-MAC) was fabricated via a facile bio-templating method using mycelium pellets as both the carbon source and the bio-template. After ZnCl2 activation and high-temperature carbonization, the specific thread-like chain structure of mycelium in the pellets can be maintained effectively. The hyphae and junctions of the cross-linking hyphae form nanowires and carbon nanoparticles that link with the neighboring nanoparticles to form a network structure. By adding NH4Cl, foreign nitrogen element doped (N-doped) 3D-MAC was obtained, which has a hierarchical porous structure composed of micropores and macropores. And the multiple pore size distribution benefits from ZnCl2 activation, the specific 3D structure and gas blowing. Meanwhile, the introduction of some hydrophilic groups and abundant N-containing functional groups in extrinsic N-doped 3D-MAC contributes to improving the Faradaic pseudocapacitance, respectively. A specific capacitance of 237.2 F g−1 at 10 mV s−1 was displayed, which is more than 1.5 times that of 3D-MAC. Even at the large scan rate of 500 mV s−1, N-doped 3D-MAC still reveals a nearly symmetric rectangular shape, demonstrating great potential as a high-performance supercapacitor electrode material due to the synergistic effects of its 3D hierarchical porous structure and various functional groups.
Highlights
Nowadays, biological adsorption is becoming widespread for the advanced treatment of sewage that contains various heavy metal ions or spilled oil[1,2]
We demonstrate that a slender hypha in the mycelium pellets can turn into a carbon nanowire via high-temperature carbonization
Based on the charge-storage mechanism, supercapacitors can be generally classified into two categories: electrical double-layer capacitors (EDLCs) in which various carbon materials are used as electrode materials and pseudocapacitors in which certain metal oxides or conducting polymers are often used as electrode materials[21,22]
Summary
The N-doped 3D-MAC shows a nearly quasi-rectangular CV curve, even at 500 mV s−1 (Fig. 5a), revealing its low contact resistance and excellent capacitive behavior at high current loads, which is mainly due to the presence of hydrophilic groups and N-containing functional groups (especially graphitic and oxidized N and pyridinic N)[37,40]. When comparing the frequencies at which capacitance drops to 50% of its maximum value (fmax, Fig. 5g inset), based on Eq (3), we clearly see that the N-doped 3D-MAC demonstrates a better frequency response (~0.058) than that of 3D-MAC (~0.043), which likely due to hydrophilic N-containing functional groups and the hierarchically porous structure of this sample (Fig. 4b)[48]
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