Simplified Chemical Synthesis of Silver Nanocubes@ZnIn₂S₄ with Different Particle Sizes for Hydrogen Production under Visible Light

Silver-based plasmonic materials have been proven to enhance the photocatalytic performance of semiconductor materials. This study investigates the effect of the size of silver nanocubes (AgNCs) on the photocatalytic activity of the semiconductor zinc indium sulfide (ZnIn2S4, ZIS). First, the optical properties and electric field distributions of Ag nanoparticles (AgNPs) and AgNCs of different sizes were analyzed using the finite-difference time-domain (FDTD) method. It was found that AgNCs exhibit unique dual-peak extinction characteristics in the visible light region, indicating their high utilization efficiency of visible light. In the experiments, AgNCs with sizes of 50 and 90 nm were synthesized and successfully combined with cubic ZIS. A rationally designed and precisely synthesized core–shell structured Ag@ZIS composite photocatalyst was developed, which facilitated directional charge transfer from Ag to cubic ZIS by leveraging the difference in Fermi energy levels. The results showed that compared to 90 nm AgNCs, 50 nm AgNCs exhibited higher photocatalytic activity. Under the condition of d(Ag):d(Ag@ZIS) = 1:3, the sample Ag@ZIS-50/150 achieved the highest hydrogen evolution efficiency under visible light, reaching 1876.42 μmol g–1 h–1, which is 38 times that of pure cubic ZIS. Furthermore, it maintained 88.4% of its activity after four cycles of hydrogen production experiments, demonstrating excellent photochemical stability. Density functional theory calculations revealed that the work function values of Ag and ZIS are Φ = 4.37 eV and Φ = 5.90 eV, respectively, further theoretically confirming the charge transfer direction from Ag to ZIS. This study not only explores the relationship between the size of AgNCs and their optical properties but also provides a research approach for improving the utilization efficiency of photocatalysts in the visible light region.