Xing Xu,Lei Lai,Tao Zeng,Yan Yu,Zhiqiao He,Jianmeng Chen,Shuang Song
The exploration of low-cost, high-performance, and stable photocatalysts for the highly efficient conversion and storage of solar energy in hydrogen is of great importance. This study presents a novel pyridine-type carbonitrides (CN)-modified surface-disordered C-doped TiO2 (PCN/CTiO2@TiO2–x) catalyst used for photocatalytic H2 evolution from water. The employed preparation method of hydrolysis–calcination has the advantages of low-cost raw materials and easy scale-up. The optimized PCN/CTiO2@TiO2–x exhibited an impressive hydrogen evolution rate of ∼3743 μmol h–1 g–1 under simulated solar light (AM 1.5) and remained stable after five cycles. The maximal quantum efficiency reached 37.5% at 370 nm and 7.0% at 400 nm, which was superior or comparable to several reported relevant TiO2-based catalysts. Benefiting from the pyridine-type CN modification, disordered surface layer (TiO2–x), and increased oxygen vacancies/Ti3+ species, the photogenerated electrons moved rapidly from the visible-response C-doped TiO2 to CN to participate in the photoreduction reaction, which led to a marked improvement in the catalytic activity.
In this paper, we present a method to enhance the stability of Fe–N–C electrocatalysts, known for their significant oxygen reduction reaction (ORR) activity and positioned as promising alternatives to commercial noble metal-based catalysts. Despite the favorable ORR activity, Fe–N–C suffers from inadequate stability in acidic media, primarily attributed the loss of active FeN 4 sites resulted from Fe-demetalation. However, recent investigation reveals that pyridine N exhibits remarkable stability in retaining Fe atoms. To address this, we achieved a high proportion of pyridine N doping in carbon nanofibers through a process involving nano-SiO 2 shell coating and electrospinning. The nano-SiO 2 shell coating method demonstrates efficacy and versatility in transforming pyrrole-type FeN 4 into pyridine-type FeN 4 , irrespective of the origin material being trivalent or divalent Fe, whether organic or inorganic.
Shaojun Chen,Zhankui Mei,Huanhuan Ren,Haitao Zhuo,Jianhong Liu,Zaochuan Ge
This paper reports a new type of zwitterionic polyurethane containing pyridine type zwitterionic segments for shape memory materials. The pyridine type zwitterionic shape memory polyurethanes (SMPUs) were synthesized using polyurethane polymerization from N,N-bis(2-hydroxylethethyl)isonicotinamide (BINA), hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BDO), followed by a ring-opening reaction with 1,3-propanesultone (PS). The structure and properties of the pyridine-type zwitterionic SMPUs (PyZPUs) were investigated systematically. The results demonstrate that the PyZPUs form phase-separation structures composed of a hard phase and an amorphous soft phase with a broad glass transition. The shape memory tests show that the PyZPUs have thermal-induced dual-shape memory effects (SMEs), triple-SMEs and quadruple-SMEs and also moisture-sensitive SMEs. Comparatively, the samples with PS/BINA molar ratios of 0.6–0.8 have more than 86% shape recovery and more than 95% shape fixity with a heat stimulus. Under moisture conditions, these samples also show the quickest moisture-sensitive strain recovery, up to 86%. Moreover, the PyZPUs show good biocompatibility when the content of pyridine type zwitterionic segments is beyond 21 wt%. Thus, the PyZPUs are expected to have many promising applications in smart biomedical fields.
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