Effects of Preparation Conditions on the Efficiency of Visible-Light-Driven Hydrogen Generation Based on Cd0.25Zn0.75S Photocatalysts

Maali-Amel Mersel,Miklós Jakab,Péter Pekker,Ottó Horváth,Lajos Fodor,Éva Makó

doi:10.3390/catal11121534

Abstract

Photocatalytic H2 production utilizing H2S, an industrial side-product, is regarded as an environmentally friendly process to produce clean energy through direct solar energy conversion. For this purpose, sulfide-based materials, such as photocatalysts, have been widely used due to their good solar response and high photocatalytic activity. In this work, a ZnS–CdS composite was studied, and special attention was dedicated to the influence of the preparation parameters on its H2 production activity. The ZnS–CdS composite, with an enhanced photoactivity for H2 production, was synthesized both from ammine complexes and, in a conventional way, directly from acetates at various pH values. Deviating from the traditional method, the photoactivity of ZnS–CdS prepared from ammine complexes was not affected by the pH. Besides, the hydrothermal treatment and the ammonia content strongly influenced the rate of H2 production in this system. DRS, TEM, SEM, XRD, and quantum yield measurements prove the dependence of the photoactivity of these catalysts on the structural and morphological properties determined by the preparation conditions. The promising photocatalytic efficiency achieved with the application of these ZnS–CdS catalysts, prepared without any metal deposition, encourages further investigations to enhance the rate of hydrogen generation by optimization of the reaction conditions for practical utilization.

Highlights

Nowadays, the main atmospheric issues arise from the increased consumption of fossil fuels, urging the development of an alternative source of energy to meet the world’s energy demand [1]
The sulfide reagent was added to the solution containing the metal ions, but in some cases a reverse order was applied [20,36]
We depicted the rate of hydrogen production (RHP) as a function of the illumination time, but in the bar diagrams, its average calculated for the 200–400 min time range is represented

Summary

Introduction

The main atmospheric issues arise from the increased consumption of fossil fuels, urging the development of an alternative source of energy to meet the world’s energy demand [1]. The most common type of photocatalysts previously used were metal oxides [6,7] such as NiO/Ta2O5K [8], ZnO/TiO2 [9], Au/ZnO [10], ZnO/Fe2O3 [11]. These materials mostly utilized ultraviolet radiation, which only represents a small part of the solar spectrum. The main sulfidebased catalysts have been reviewed by Zhang and Guo; most of them consist of block d transition metals with d10 electron configuration, and the most investigated type was CdS or ZnS–CdS [12]. The Fe2O3/ZnS–CdS core–shell nanoparticles were prepared for this purpose [15]

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Conclusion