Soft carbon has been regarded as one of the most promising anode materials for potassium-ion batteries. However, the rearrangement of planar aromatics at high carbonization temperature usually yields a highly graphitized structure, which generally leads to inferior rate and cycle performance. In addition, the role of intrinsic carbon defects on potassium storage has not been well reported yet. In this work, crosslinked pitch-based soft carbon nanosheets have been synthesized through the iodination/dehydroiodination process at low temperature and carbonization with NaCl template. The iodine-treatment efficiently crosslinks the planar aromatics to three-dimensional framework by alkyl-bridged linkages, and reduces the strong π-π interaction during carbonization. This unique microstructure yields an ordered-in-disordered carbon microstructure, enlarged interlayer spacing, and abundant intrinsic defect sites. Benefited from these merits, the optimal sample displays 140% increase of reversible capacity to the pristine pitch-based carbon at 5 A g −1 . Particularly, it also presents 87.4% capacity retention after 1000 cycles at 1 A g −1 . This facile but simple strategy is expected to expand to other high-performance carbon materials and further understand the effect of intrinsic defects for potassium storage and beyond.
Herein, a zeolite-like metal-organic framework (MOF, i.e., ZIF-67) is treated with I 2 at 170 °C and without any solvents and inert atmospheres to obtain the oxygen reduction reaction (ORR) catalysts (i.e., I 2 &ZIF-67). After treated with I 2 , the ORR activity of I 2 &ZIF-67 in alkaline electrolyte has been significantly increased compared with the pristine ZIF-67. Particularly, the optimized I 2 &ZIF-67(2:1) shows the half-wave potential of ∼0.83 V and Tafel slope of ∼37.3 mV per current decade, which is comparable to 20 wt% Pt/C. The enhanced ORR activity is mainly attributed to the generation of active pyridinic-N, Co 2+ and I 3 − species induced by the interaction between I 2 and ZIF-67. Moreover, the I 2 treatment also facilitates the charge and mass transfer for ORR. This work provides a strategy to develop highly efficient ORR catalysts derived from MOFs at low temperature.
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