Facile synthesis of sphere-like structured ZnIn2S4-rGO-CuInS2 ternary heterojunction catalyst for efficient visible-active photocatalytic hydrogen evolution

Abstract

Photocatalysis is a promising approach for generating hydrogen, an eco-friendly and cost-effective fuel. It is hypothesized that the ternary catalyst ZnIn₂S₄-rGO-CuInS₂, prepared by ultrasonication method, should be effective for optimized photocatalytic hydrogen generation in a Na₂S/Na₂SO_3-water mixture. The as-synthesized catalyst was characterized using various surface analytical and optical techniques. Field-emission scanning electron microscopy and high-resolution transmission electron microscopy analyses revealed that marigold-like structured ZnIn₂S₄ and layer-structured CuInS₂ were dispersed on the reduced graphene oxide sheets. The ternary ZnIn₂S₄-rGO-CuInS₂ system showed enhanced photocatalytic H₂ production compared to pure ZnIn₂S₄, CuInS₂, ZnIn₂S₄-rGO, CuInS₂-rGO, and ZnIn₂S₄-CuInS₂ catalysts under visible light illumination. The fabricated ZnIn₂S₄-rGO-CuInS₂ catalyst afforded hydrogen generation of 2531 μmol/g after 5 h. The enhanced performance of the ZnIn₂S₄-rGO-CuInS₂ catalyst originates from the synergetic effect with rGO as the electron transfer medium, and is confirmed by photocurrent density and photoluminescence measurements that indicate reduced recombination between the excited electron and hole pairs, and fast electron transfer in the ternary composite. The excellent performance of the ZnIn₂S₄-rGO-CuInS₂ catalyst for up to three consecutive cycles was demonstrated in cyclic stability tests under visible-light illumination.

Keywords: Hydrogen evolution; Photocatalysis; Photocurrent density; Reduced graphene oxide; Ternaryphotocatalyst; Visible light illumination.