Abstract
The aim of this work is to study the influence of the sulphur source (elemental sulphur, thiourea and L-cysteine) in the solvothermal synthesis of Ag-CdS over its growth, structuration and state of Ag and how these changes influence on its photoactivity. The differences in the generation rate of the S2− from the sulphur sources during the solvothermal synthesis determine the nucleation and growth pathways of CdS affecting to the silver state and its incorporation into the CdS lattice. The hydrogen production on Ag-CdS photocatalysts decreases according the sequence: thiourea > elemental sulphur >> L-cysteine. The changes in the photoactivity of Ag-CdS samples are analysed in terms of the differences in the insertion of Ag+ into the CdS lattice, the formation of composites between CdS and Ag2S and the formation of CdS crystalline domains with strong confinement effect derived from the different sulphur source used in the solvothermal synthesis.
Highlights
The use of hydrogen, both as a fuel and as an energy carrier, is one of the most feasible alternatives to decarbonise the energy production system, decreasing the greenhouse gas emissions that accelerate the global warming
We found that CdS modified with Ag prepared by solvothermal method leads to the incorporation of Ag+ in the CdS lattice and/or as Ag2 S heterojunctions depending on the conditions used in the solvothermal synthesis [44]
With regards to the silver concentration on the Ag-modified CdS photocatalysts (AgCdS)-X samples, it was observed important differences in its surface concentration according to the sequence: AgCdS-T > AgCdS-L > AgCdS-S
Summary
The use of hydrogen, both as a fuel and as an energy carrier, is one of the most feasible alternatives to decarbonise the energy production system, decreasing the greenhouse gas emissions that accelerate the global warming. In the near future, the renewable resources must be used for hydrogen production as a way to decouple it from the carbon cycle [3,4,5] Among the renewable ways to produce hydrogen, those that use water and solar light are the most interesting, especially those based on photocatalytic processes. The photocatalytic production of hydrogen has raised great interest over the past decades because of its simplicity and because it uses two of the most abundant renewable resources: water and solar light. This process requires the use of efficient photocatalysts active under solar light, and several semiconductor materials based on oxides, sulphides, nitrides, oxynitrides or phosphides have been studied and developed [6,7]. In spite of the intense research in this field, the increase of their efficiency to reach 10% required for practical applications still remains as the main challenge
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