Enhanced photocatalytic hydrogen production over In-rich (Ag–In–Zn)S particles

The ratio of ZnS to AgInS2 is usually adjusted to tune the band gaps of this quaternary (Ag–In–Zn)S semiconductor to increase photocatalytic activity. In this study, the [Zn]/[Ag] ratio was kept constant. The hydrogen production rate was enhanced by increasing the content of indium sulfide. Compared to the steady H2 evolution rate obtained with equal moles of indium and silver ([In]/[Ag] = 1, 0.64 L/m2 h), that obtained with In-rich photocatalyst ([In]/[Ag] = 2, 3.75 L/m2 h) is over 5.86 times higher. The number of nanostep structures, on which the Pt cocatalysts were loaded by photodeposition, increased with the content of indium. The indium-rich samples did not induce phase separation between AgxInxZnyS2x+y and AgIn5S8, instead forming a single-phase solid solution. Although the photocatalytic activity decreased slightly for bare In-rich photocatalysts, Pt loading played a critical role in the hydrogen production rate. This study demonstrates the significant effect of In2S3 on this unique (Ag–In–Zn)S photocatalyst.