Fabrication And Performance Of Silicon Nanowires-based Core-shell Composite Photocatalysts

Semiconductor photocatalysis is regarded as a promising technology to availably alleviate ever-growing environment and energy crisis.One-dimensional silicon nanostructures has attracted intense attention in photocatalysis,owing to their exceptional properties,such as their unique geometrical characteristics in providing large aspect-ratio,fast charge transport,strong light trapped capacity as well as large surface area.However,nanostructures composed of bare silicon material exhibit low quantum efficiency and unstable surface features in solar to chemical energy conversion,which greatly limits practical applications.Therefore,the development and design of silicon-based composite photocatalysts with enhanced photocatalytic performance and photostability have an excellent scientific significance for facilitating the application of silicon nanostructures in photocatalysis.In this article,silicon nanowires arrays was chosen as a substrate material,and the effect of morphology tuning,interface modification and introduction of other components of silicon nanowires on their photocatalytic properties have also been investigated.(1)The well-aligned silicon nanowires arrays with large-up production and porous structures was synthesized by a facile metal-assisted wet chemical etching method.(2)The vertically aligned silicon nanowires@CdS quantum dots arrays are constructed by via a facile electrostatic self-assembly approach.The as-prepared samples show obviously higher photocatalytic activity than that of pure silicon nanowires toward water splitting into hydrogen gas and selective reduction of paranitroanilinum in water under visible light irradiation.The photoelectrochemical analysis proves the formation of the p-n junction between p-type silicon nanowires and n-type CdS quantum dots.This p-n junction not only facilitates efficient separation of photogenerated charge carriers,but also retards photocorrosion effect of CdS quantum dots,therefore leading to the enhance photocatalytic property and photocatalytic stability.In addition,composite photocatalysts with film structure bestow it with readily recycling virtue.It is anticipated that this work opens up an appealing strategy for the development and applications of other p-n junction photocatalysts.(3)The high-performance silicon nanowires was fabricated via the optimization of its length based on the etching time tuning.The obtained silicon nanowires was coupled with cobaltosic oxide to form core-shell composite photocatalyst through one-step calcination method,and it was applied for photocatalytic water splitting into hydrogen gas.The composite displays excellent photocatalytic activity and stability as compared to the bare silicon nanowires.In accordance with experiment data and theoretical analysis,a novel direct z-scheme electrons transport was presented for clearly explaining reaction mechanism,facilitating separation of photoinduced electron-hole pairs and thus improving photocatalytic performance and stability.