| At present,photocatalytic hydrogen production technology is one of the most prospective techniques to produce clean energy,supplying an effective way to convert solar energy into hydrogen as a renewable green fuel.At the same time,photocatalytic technology can also degrade organic pollutants in wastewater to protect environment.Therefore,it is the key to sustainable development to exploit new-typed peculiarly structural and functional heterojunction photocatalysts with cost-effectiveness,high efficiency and easy recovery.Carbon-based photocatalyst has excellent photocatalytical performance owing to its strong charge carriers transportation capacity.Presently,there is no report about the special carbon-based Janus-structure photocatalyst.Hence,it is a vital research topic to construct Janus-structure carbon-based nanofiber photocatalyst and to study its characteristics.In this dissertation,three kinds of unique Janus-structure carbon-based nanofiber heterojunction photocatalysts were prepared by conjugate electrospinning,carbonization and gas-solid reaction,and the structures,morphologies and photocatalytic properties are detailedly investigated.The details are as follows:1.Flexible self-supporting [Ti O2/C]//[Bi2WO6/C] Janus nanofiber heterojunction photocatalysts were prepared by the combination of conjugated electrospinning followed by carbonization process.Under visible light and simulated sunlight irradiation,the photocatalyst respectively achieves high hydrogen evolution rates of 11.58 and 16.32 mmol·h-1·g-1,and further the photo-degradation rates of methylene blue?MB?respectively are 93.3%?160 min?and 97.9%?140 min?.Self-supporting photocatalyst has excellent flexibility,recyclability and cycle stability.2.Carbon-based [g-C3N4/C]//[Ti O2/C] Janus nanofiber heterojunction photocatalysts were constructed by the combination of conjugated electrospinning with carbonization technique.By using betaine as foaming agent,g-C3N4 and Ti O2 nanoparticles are uniformly distributed on the surface of Janus nanofibers,thus providing Janus nanofibers with excellent photocatalytic activity.Under visible light and simulated sunlight irradiation,the high hydrogen evolution rates of 12.40 and 16.72 mmol·h-1·g-1 are obtained,respectively,and the photo-degradation rates of MB are respectively 95.1%?160 min?and 98.6%?140 min?.Therefore,the photocatalyst achieves the bifunctional characteristics of efficient hydrogen evolution and degradation of organic pollutants.3.By using [Ti O2/C]//[Bi2WO6/C] Janus nanofiber photocatalyst as the substrate and urea as the gas phase precursor,ultra-thin g-C3N4 nanosheets were fabricated and anchored on the surface of Janus nanofibers via gas-solid reaction.By adjusting the content of urea powders,the density,thickness and loading amount of g-C3N4 nanosheets on Janus nanofibers can be easily modulated.Under visible light and simulated sunlight illumination,the optimized photocatalyst achieves high hydrogen evolution rates of 13.05 and 17.48 mmol·h-1·g-1,respectively,and the photo-degradation rates of MB respectively reach 97.0%?120 min?and 99.2%?100 min?.The above three types of Janus structure carbon-based nanofiber photocatalysts possess excellent photocatalytical performances mainly owing to the synergistic effect among extension of light absorbance,formation of heterojunction and one-dimensional conductive carbon nanofiber matrix.The new findings provide a new perspective for the development of other high-efficient and recyclable photocatalysts. |
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