Nickel-catalyzed formation of mesoporous carbon structure promoted capacitive performance of exhausted biochar

Biochar is widely studied to adsorb heavy metals in wastewater, while the reclamation of exhausted biochar becomes a challenge. In this study, biochar adsorbing Ni2+ with two concentration levels were used as precursors to prepare electrical double layer capacitor (EDLC) materials. A good performance of capacitance (188.9 F g(-1) at 0.5 A g(-1)) and stability (capacitance retention maintained 95.9% after 1000 cycles) were achieved with the precursor of nickel-laden biochar of 100 mg g(-1) and activation temperature of 600 degrees C, while the capacitance of control without nickel was only 98.4 F g(-1). Power X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer-Emmete-Teller (BET) and the Raman Imaging combined with Emission Scanning Electron Microscope (RISE) identified that metallic nickel promoted carbonate decomposition and invaded into carbon layer, which assisted mesopores (551.8 m(2) g(-1)) formation and contributed to a high capacitance. Moreover, nickel catalyzed the transfer of sp(3) carbon to sp(2) hybridization, which enhanced the conductivity and stability of EDLC. This study provides a feasible and simple strategy of reclaiming waste biochar after adsorbing nickel to prepare energy intensive material and implies the possibility and necessity of cascading applications of biowastes from environmental remediation to energy storage.

Automated summary

By adsorbing nickel onto exhausted biochar and utilizing it as a precursor for preparing electrical double layer capacitor (EDLC) materials, this study achieved improved capacitance performance and stability. The presence of metallic nickel promoted carbonate decomposition and invaded into the carbon layer, enhancing mesopores formation and contributing to high capacitance. Furthermore, nickel catalyzed carbon hybridization transformation, enhancing the conductivity and stability of EDLC.