(215ae) Uniform Single Crystalline Sulphide-Based Quaternary Alloy Hexagonal Nanorings for Highly Efficient Photocatalytic Hydrogen Evolution

Sulphide-based polynary alloy semiconductors are ideal photoabsorbers for solar energy applications because of their tunable electronic and optical properties. [1] Compared to binary materials, polynary alloy semiconductor nanomaterials are able to produce new properties while inheriting the properties from their parent binary materials. For example, the energy bandgap of polynary alloys could be precisely tuned by controlling the composition of alloyed nanomaterials without changing their size and shape, which leads to wider wavelength absorption over the visible to ultraviolet light range. [2] A common difficulty in the applications of these alloyed materials lies in achieving compositional homogeneity and morphological controllability due to the diverse starting materials having varying reactivity. Cation-exchange reactions can lead to the formation of Zn_xM_1-xN (M=Cu, Cd etc, N=S, Se) polynary compounds with controlled composition and structure from their parent binary materials, which results in efficient H₂evolution in overall water splitting [3]. In principle, the solubility of involved materials is critical for the feasibility of ion-exchange reaction, and the products from ion-exchange reaction must be of a lower solubility than the initial ones. Most of the recent reports on ion-exchange reactions mainly involved binary compounds; their application in polynary alloy nanocrystals synthesis is still uncommon. In addition, the photocorrosion usually occurred in sulphide-based photocatalysts, which caused the degradation of their photocatalytic property.

In this work, we report an original ion-induced synthetic strategy to prepare single crystalline quaternary sulphide uniform nanorings (Cu-MIn_xS_y) with homogenous structure induced by metal ions. The Cu²⁺-doped NaInS₂ nanorings were first synthesized via a copper ions induced Kirkendall effect, and the as-synthesized products could be further transformed to other quaternary sulphide nanorings by solubility induced cation-exchange strategy. Because of the higher solubility of sodium salts than that of other metals, this method presents a general strategy to fabricate quaternary sulphide alloys with defined morphology and structure (not limited to nanorings), and could be extended to the synthesis of other quaternary alloys with similar layer structure as the NaInS₂ nanocrystals. Furthermore, the as-synthesized quaternary sulphide nanorings exhibit efficient activity and good stability for photocatalytic H₂ evolution from water splitting. [4]

Reference:

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[4] P. Hu, S. S. Pramana, S. Cao, C. K. Ngaw, J. Lin, S. C. Joachim Loo, T.T.Y. Tan, Adv Mat, 2013, 25, 2567-2572.