Nitrogen self-doped graphitic carbon nitride (C3N4+x) was successfully synthesized by the co-thermal condensation of the precursor with a nitrogen-rich additive. The resultant self-doped semiconductor was characterized by X-ray photoelectron spectroscopy (XPS), which indicated that the nitrogen atom substituted the sp2 carbon atom. The photocatalytic hydrogen evolution was systematically evaluated under visible light irradiation (λ > 400 nm). The average hydrogen evolution rate for C3N4+x was 1.8 times higher than that of pristine graphitic carbon nitride, and the superiority lay in greatly improved optical, emission and electronic properties of the nitrogen modified carbon nitride. This study filled the research gap of self-doping for 2D polymeric carbon nitride and will stimulate intensive investigations in the further improvement of photocatalytic hydrogen evolution.
Qiwen Jiang,Yeyan Ni,Qi Zhang,Jiafeng Gao,Ziqi Wang,Huanhuan Yin,Yi Jing,Jie Wang
Herein, a cost-effective, green, and sustainable method was developed to fabricate N self-doped carbon nanofibers (CChCNs) as anodes for high-performance lithium-ion batteries (LIBs). After simple direct pyrolysis of biomass chitin nanocrystals (ChCNs), a novel precursor, the obtained CChCNs presented a cross-linked fibrous structure with large specific surface areas and hierarchical porous structures, which was instrumental in charge-storage capacity for LIBs. As expected, the as-prepared CChCNs exhibited distinguished lithium storage properties. It was found that the increase in conductivity could optimize charge and discharge under high current densities. CChCNs900 possessed a reversible specific capacity of 215 mA h g–1 at 1.5 A g–1. In addition, all the samples presented excellent cycle stability, possessing capacity retention of 46.2, 67.4, 77.4, and 74.5% after a 500 cycle at a high current density of 1 A g–1. This novel strategy provided a successful avenue to prepare high-performance LIB anodes from biomass nanomaterials.
Ling Meng,Zhaoxia Sun,Guanghang Sun,Xiting Zhang,Meng Dan,Jin Long,Jian Hu
Herein, we reported that KOH impregnation can generate a large number of porous structures with fruitful nitrogen self-doped groups during the carbonized process for poly (p-phenylene terephthalamide) fiber and poly (p-phenylene benzobisoxazole) fiber (denoted as PPTA and PBO, respectively). The intrinsical insulation, volume change, and shuttle effect of polysulfides then can be more significantly improved for the PBO-coated separator than the PPTA case. The discharge capacity primary achieves 1,322 mA h/g, which retains 827 mA h/g even after 200 cycles at 0.2 C for the cell with PBO-coated separator. The reversible specific discharge capacity maintains 841 mA h/g with a Coulomb efficiency of 99.7% at 5 C. The nitrogen self-doped nanocarbon particles are etched by KOH with the simple one-step preparation, which has promising application as Li-S battery cathode.
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