Abstract
Nowadays, the study of environmentally friendly ways of producing hydrogen as a green energy source is an increasingly important challenge. One of these potential processes is the heterogeneous photocatalytic splitting of water or other hydrogen sources such as H(2)S or its alkaline solution. The most common catalysts used for H(2) production from Na(2)S solution are the CdS-ZnS type catalysts, whose efficiency can be further enhanced by Ni-modification. In this work, the surface of Cd(0.5)Zn(0.5)S composite was modified with Ni(II) compound for photocatalytic H(2) generation. Besides two conventional methods, impregnation was also applied, which is a simple but unconventional modification technique for the CdS-type catalysts. Among the catalysts modified with 1% Ni(II), the impregnation method resulted in the highest activity, for which a quantum efficiency of 15.8% was achieved by using a 415 nm LED and Na(2)S-Na(2)SO(3) sacrificial solution. This corresponded to an outstanding rate of 170 mmol H(2)/h/g under the given experimental conditions. The catalysts were characterized by DRS, XRD, TEM, STEM-EDS, and XPS analyses, which confirmed that Ni(II) is mainly present as Ni(OH)(2) on the surface of the CdS-ZnS composite. The observations from the illumination experiments indicated that Ni(OH)(2) was oxidized during the reaction, and that it therefore played a hole-trapping role.