Microwave-assisted rapid synthesis of Cu₂S:ZnIn₂S₄ marigold-like nanoflower heterojunctions and enhanced visible light photocatalytic hydrogen production via Pt sensitization

In this work, a rapid microwave synthesis route is presented for the fabrication of morphology-controlled Cu₂S: ZnIn₂S₄ marigold-like nanoflower heterojunction photocatalysts. The Cu-to-Zn-metal -cation (Cu:Zn) ratios were used to control the Cu₂S: ZnIn₂S₄ heterojunction during the second step of microwave synthesis. The formation of Cu₂S: ZnIn₂S₄ heterojunction is evidenced by XRD, TEM and XPS analyses. The optimum electronic interaction aids to stimulate electron-hole charge separation kinetics and promote the solar hydrogen (H₂) evolution performance in microwave-assisted 5 mol.% Cu₂S:ZnIn₂S₄ (Cu₂S:ZIS–5) heterojunction. Benefiting from the synergy between marigold-like morphology, heterojunction, and Pt loading, the optimum Pt loaded Cu₂S: ZIS–5 marigold nanoflowers (Pt/Cu₂S:ZIS–5) exhibited the 862 µmol of photocatalytic H₂ production after 3 h under visible light irradiation (≥420 nm). The time-resolved PL spectrum showed more than double carrier lifetime in Pt/Cu₂S: ZIS–5 heterojunction (45 ns) than that of Pt/ZIS–15 (20 ns). These visible light-responsive Pt/Cu₂S:ZIS marigold-like nanoflower heterojunction shows promising photostability, which would open new opportunities for the development of highly efficient ternary metal-chalcogenide photocatalysts for solar hydrogen generation.