Control on the homogeneity and crystallinity of Zn0.5Cd0.5S nanocomposite by different reaction conditions with high photocatalytic activity for hydrogen production from water

Abstract

Zn0.5Cd0.5S nanoparticles with phase homojunctions were prepared by a one-step hydrothermal method with thioacetamide as sulfur source. The effects of the various reaction conditions, such as initial concentrations of Zn and Cd ions, initial content of sulfur source in the reaction mixture, and the temperature rising rate, are investigated. The photocatalytic activities for H2 evolution from water in the presence of sacrificial reagents of these Zn0.5Cd0.5S nanoparticles were significantly affected by the reaction conditions. These differences on the photocatalytic activities can be attributed to the different homogeneity and crystallinity of the nanoparticles prepared at different reaction conditions. A faster reaction rate leads to the formation of Zn0.5Cd0.5S nanoparticles with bad crystallinity, but good homogeneity. On the contrary, a slow reaction rate results in a bad homogeneity, but better crystallinity. Combination of good crystallinity and homogeneity in a Zn0.5Cd0.5S nanocomposite resulted in an excellent photocatalytic activity. The highest rate of H2 evolution achieved for these phase-homojunctions materials under visible-light irradiation (λ ≥ 420 nm) reached 1252.7 μmol h−1 with an apparent quantum efficiency of 21.46% at 420 nm. The H2 evolution rate did not reduce distinctively in a continuous 15 hour test for H2 evolution, indicating an excellent stability for this material. This work not only demonstrates a facile method to produce highly active phase-homojunctions containing Zn0.5Cd0.5S solid solutions for photocatalytic hydrogen production from the perspective of controlling various reaction conditions, but also provides new insights into understanding the importance of the homogeneity and crystallinity for enhancing photocatalytic activity and stability of Zn0.5Cd0.5S solid solutions. It is expected that the strategies of modifying the homogeneity and crystallinity by controlling various reaction conditions can be extracted and used when designing other efficient and robust photocatalysts in the future.