Proper interface and band alignment always play essential roles in the separation of photoexcited charge of photocatalysts. In this work, we prepared a homodispersed S-scheme carbon nitride homojunction with local electron structure difference by a facile pre-doping and two-step calcination approach. Boron doping into heptazine created extra acceptor impurity, and phosphorus doping into heptazine created extra donor impurity, which eventually modulated the electronic structure of carbon nitride. As heptazines with different element doping were integrated into carbon nitride by recalcination, B–CN and P–CN formed a homodispersed homojunction and thus produced a rich interface. Meanwhile, caused by Fermi energy levels equilibrium, the band bending constructed an S-scheme homojunction, which stimulated photogenerated electrons to transfer from CB of B–CN to VB of P–CN. The homodispersed S-scheme homojunction structure led to efficient suppression of recombination of photoinduced charge and retained stronger redox charge. Consequently, the photocatalytic performance was dramatically boosted to 2620 μmol g −1 from 60 μmol g −1 of pure CN in 4-h hydrogen evolution from water. This novel method for electron structure engineering helped to provide a new strategy for designing homojunction photocatalysts with excellent photocatalytic performance.
Guobo Huang,Siqi Huo,Jiahao Ren,Wei Chen,Haiqin Yang,Shenwei Xiao,Tianle Wang,Hong Peng,Pingan Song
The nanomaterials have been deeply explored as flame retardants for various polymeric materials due to their multifunctionality, but they often fail to significantly increase the limiting oxygen index (LOI) and vertical burning UL-94 rating, thus unable to meet industrial needs (LOI>27.0 % and UL-94 V-0 rating). Herein, we fabricated a cerium/phosphorus-doped g-C 3 N 4 (Ce/P-CN) nanohybrid as a multifunctional high-efficiency fire retardant for acrylonitrile–butadiene–styrene (ABS). The Ce/P-CN nanoflakes featured a strengthening effect towards ABS, 10 wt% of which increased the tensile strength of ABS/(Ce/P-CN) by 33.8 %. Meanwhile, the ABS/(Ce/P-CN) nanocomposites showed remarkably enhanced high-temperature stability and carbonization performances relative to virgin ABS. Ce/P-CN simultaneously improved the anti-ignition, fire retardancy and smoke suppression of ABS due to the barrier effect of g-C 3 N 4 nanoflakes and the catalytic carbonization effect of cerium and phosphorus. Notably, adding 10 wt% Ce/P-CN increased the LOI and UL-94 rating of ABS to 28.6 % and V-0, respectively, demonstrating its high flame-retardant efficiency. Thus, the high flame-retardant efficiency and multifunctionality enable Ce/P-CN to outperform previous flame retardants for ABS. This work offers a novel strategy for the development of high-efficiency g-C 3 N 4 nanoflakes, which endow ABS with improved mechanical robustness and fire retardancy and show broad industrial prospects.
Wenting Chen,Hua Liang,Xin Wen,Zongchen Li,Hui Xiong,Qiang Tian,Minhao Yan,Yuanzhi Tan,Guy Royal
To explore the effect of sensor structure on anions detection, three new hydrazones P-CN , P-CF 3 and P-NO 2 having different electron-withdraw groups are synthesized. Their anions recognition properties are investigated compared with those of P-OMe , P-H and acylhydrazone B-NO 2 . It shows all non-nitro hydrazones exhibit increasing sensitivity specifically toward CN − in the order of P-OMe < P-H < P-CN < P-CF 3 , indicated by color change from colorless to different shades of blue. Whereas P-NO 2 responds to CN − , F − and H 2 PO 4 − concurrently and its sensitivity to CN − is more than 4 times higher compared with that of the other hydrazones. CN − can be discriminated from F − by P-NO 2 in acetonitrile/water. On the other hand, B-NO 2 has only discernible response to CN − and F − with less sensitivity than P-NO 2 does. Detection details of P-NO 2 to CN − are investigated by titration, anti-interference tests, Job’s plot, HRMS, pH effect assays. The 1 H NMR, IR and reversibility tests demonstrate the deprotonation mechanism. The detection mechanisms of P-NO 2 and B-NO 2 to CN − are compared and demonstrate the reason of their recognition difference. The detection limits of P-NO 2 to CN − , F − and H 2 PO 4 − in acetonitrile are 0.0477 μM, 0.0876 μM and 1.46 μM, respectively. Hence, this work indicates that strong electron-withdraw group in related probes can improve their anion detection ability, meanwhile conjugation effect should be also considered in structure designing.
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