Controlled Synthesis Of Nanosheet-assembled Cu₉S₅ Hollow Polyhedra And Their Enhanced Photocatalytic Activities

Copper sulfide?Cux S?,as a non-stoichiometric p-type semiconductor with unique optical and electrical properties,the bandgap is 1.2-2.2e V,has been widely investigated in the potential application of solar cells,photoelectric transformers,gas sensors,and lithium-ion batteries.With the development of nanotechnology,the construction of Cux S hollow hierarchical structures was regard as a simple and effective way to improve performance.However,most available products are mostly built up by random aggregation of granular subunits and rarely established by well-aligned rod-/sheetlike subunits via a simple,low-cost and environmentally friendly method.Thus,the design of a simple,low cost and environmentally friendly method to construct nanorods/sheets assembled hollow hierarchical nanostructures is important for boosting their performances and accelerating the development of Cux S in application area.In this paper,we report a low temperature solution phase method to prepared nanosheet-assemabled Cu₉S₅ hollow 26-facet polyhedra by Cu₂O as a template,Na2 S as a sulfur sources.At the same time,the morphology and structure of product with the change of synthesis conditions,possible formation mechanism and photocatalytic performance were discussed.The results are as follows:?1?Solid Cu₂O 26-facet polyhedral serve as not only the starting materials,but also the site of sacrificial self-templates.The Kirkendall effect-controlled self-template mechanism from sacrificial Cu₂O solid crystals to Cu₉S₅ hollow polyhedra is proposed based on observations from a time-dependent hollowing evolution process.We synthesized Cu₂O@Cu₉S₅ yolk-shell heterostructure cages by controlling the degree of hollowing based on kirkendall effect hollow mechanism.Cu₉S₅ hollow nanostructure with 26-facet polyhedral shape have hollow and porous configuration that may guarantee more surface area and pass route that providing more active sites for degradation reactions.With the assistance of hydrogen peroxide?H2O2?,at 1h,the degradation rate of MB can reach 95%.?2?Cu₉S₅ hollow nanostructure with 26-facet polyhedral shape are constructed of a number of interlaced sheetlike primary building blocks with 50-100 nm in thickness and hundreds of nanometers in planar size.?3?During this process,sodium hydroxide is found to be critical for the formation of discrete and uniform Cu₉S₅ hollow polyhedra under the fast sulfidation and crystal growth.It is noted that Cu₉S₅ hollow polyhedra can still be prepared in the absence of sodium hydroxide during the sulfidation process,but these hollow polyhedra mix with many ill-defined aggregates and are poorly dispersed with a wide size distribution.The reason could be attributed to higher nucleation rate and uncontrolled rapid crystal growth.With the assistance of sodium hydroxide solution,it is found that during the sulfidation process,sodium hydroxide has no obvious effect on the hollowing evolution.?4?The temperature have important effect on morphological and structural of product during the sulfidation process.When the temperature is maintain at 20 ?,the obtained products are composed of numerous sheetlike aggregates without uniform morphologies and no hollow hierarchical structures are formed.The primary nanosheets are about 1.5-3?m in planar size with a representative thickness of about 100 nm.When temperature is increased to 40 ?,the as-prepared products are constructed of a large number of uniform hierarchical Cu₉S₅ polyhedral structures and there are few residual dispersive nanosheets.When temperature is increased to 60 ?,the as-prepared products are constructed by nanosheet-assembled Cu₉S₅ hollow polyhedral.When the temperature is eventually fixed at 80 ?,the as-prepared products are constructed by numerous nanoparticle-assembled Cu₉S₅ hollow structure aggregates with ill-defined shape,indicating that too higher temperature inhibits the anisotropic growth of Cu₉S₅ to preferentially form sheetlike shape and further the self-assembly of uniform hierarchical structures.?5?The present sulfuring route offers additional possibility of constructing unique Cu₉S₅ nanostructures via using different Cu₂O polyhedra as sacrificial templates,such as cubes,cuboctahedra,and octahedra.