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Highly Efficient Photocatalytic Hydrogen Production of Flower-like Cadmium Sulfide Decorated by Histidine.

Wang Q, Lian J, Li J, Wang R, Huang H, Su B, Lei Z - Sci Rep (2015)

Bottom Line: Superior photocatalytic activity relative to that of pure CdS is observed on the flower-like CdS photocatalyst under visible light irradiation, which is nearly 13 times of pure CdS.On the basis of the results from SEM studies and our analysis, a growth mechanism of flower-like CdS is proposed by capturing the shape evolution.The imidazole ring of L-Histidine captures the Cd ions from the solution, and prevents the growth of the CdS nanoparticles.

View Article: PubMed Central - PubMed

Affiliation: College of Chemistry and Chemical Engineering, Northwest Normal University, Key Laboratory of Eco-Environment-Related Polymer Materials, Ministry of Education of China, Key Laboratory of Gansu Polymer Materials, Lanzhou 730070, China.

ABSTRACT
Morphology-controlled synthesis of CdS can significantly enhance the efficiency of its photocatalytic hydrogen production. In this study, a novel three-dimensional (3D) flower-like CdS is synthesized via a facile template-free hydrothermal process using Cd(NO3)2•4H2O and thiourea as precursors and L-Histidine as a chelating agent. The morphology, crystal phase, and photoelectrochemical performance of the flower-like CdS and pure CdS nanocrystals are carefully investigated via various characterizations. Superior photocatalytic activity relative to that of pure CdS is observed on the flower-like CdS photocatalyst under visible light irradiation, which is nearly 13 times of pure CdS. On the basis of the results from SEM studies and our analysis, a growth mechanism of flower-like CdS is proposed by capturing the shape evolution. The imidazole ring of L-Histidine captures the Cd ions from the solution, and prevents the growth of the CdS nanoparticles. Furthermore, the photocatalytic contrast experiments illustrate that the as-synthesized flower-like CdS with L-Histidine is more stable than CdS without L-Histidine in the hydrogen generation.

No MeSH data available.


Schematic of the growth process of flower-like CdS (This Figure was drawn by our co-author Jiajia Li).
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f4: Schematic of the growth process of flower-like CdS (This Figure was drawn by our co-author Jiajia Li).

Mentions: On the basis of the SEM observation and the experimental process, a possible mechanism is proposed to explain the formation of flower-like CdS, as depicted in Figure 4. Firstly, the imidazole rings of L-Histidine capture Cd ions to form Cd (II) bis-hitidinato complex (Figure 5) and prevent the agglomeration of CdS by releasing cadmium ions slowly into the solution1718. And then, Cd2+ and thiourea might form Cd-thiourea complex because of the strong coordinating capacity of the thiourea. With increasing temperature during the hydrothermal process, the Cd-thiourea complex may tend to decompose to release active Cd2+ and S2–. Then the active Cd2+ reacts with active S2– to form CdS seeds. L-Histidine plays a key role in the formation of flower-like CdS. The nitrogen atom of the imidazol ring promotes its solubility in aqueous solution and is also an important element to produce hydrogen-bond interaction between particles19. At the beginning of reaction, the number of CdS particles is small, and L-Histidine can effectively chelate most surfaces of the originally formed aggregates CdS. When the particles closely contact with each other, diffusion-controlled growth occurs in the spherical aggregates, and the surface area is reduced by particle fusion and structure rearrangement20. At this stage, some spheres with a rough surface are obtained. With the formation of more and more CdS nanoparticles, the petals appear from the primal multiplayer surface structure and then flower-like structures are generated. This mechanism is similar to the oriented attachment, which was observed in a system where small particles were coated with small molecules and the molecules allowed them to get close to each other and to facilitate attachment21.


Highly Efficient Photocatalytic Hydrogen Production of Flower-like Cadmium Sulfide Decorated by Histidine.

Wang Q, Lian J, Li J, Wang R, Huang H, Su B, Lei Z - Sci Rep (2015)

Schematic of the growth process of flower-like CdS (This Figure was drawn by our co-author Jiajia Li).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4559807&req=5

f4: Schematic of the growth process of flower-like CdS (This Figure was drawn by our co-author Jiajia Li).
Mentions: On the basis of the SEM observation and the experimental process, a possible mechanism is proposed to explain the formation of flower-like CdS, as depicted in Figure 4. Firstly, the imidazole rings of L-Histidine capture Cd ions to form Cd (II) bis-hitidinato complex (Figure 5) and prevent the agglomeration of CdS by releasing cadmium ions slowly into the solution1718. And then, Cd2+ and thiourea might form Cd-thiourea complex because of the strong coordinating capacity of the thiourea. With increasing temperature during the hydrothermal process, the Cd-thiourea complex may tend to decompose to release active Cd2+ and S2–. Then the active Cd2+ reacts with active S2– to form CdS seeds. L-Histidine plays a key role in the formation of flower-like CdS. The nitrogen atom of the imidazol ring promotes its solubility in aqueous solution and is also an important element to produce hydrogen-bond interaction between particles19. At the beginning of reaction, the number of CdS particles is small, and L-Histidine can effectively chelate most surfaces of the originally formed aggregates CdS. When the particles closely contact with each other, diffusion-controlled growth occurs in the spherical aggregates, and the surface area is reduced by particle fusion and structure rearrangement20. At this stage, some spheres with a rough surface are obtained. With the formation of more and more CdS nanoparticles, the petals appear from the primal multiplayer surface structure and then flower-like structures are generated. This mechanism is similar to the oriented attachment, which was observed in a system where small particles were coated with small molecules and the molecules allowed them to get close to each other and to facilitate attachment21.

Bottom Line: Superior photocatalytic activity relative to that of pure CdS is observed on the flower-like CdS photocatalyst under visible light irradiation, which is nearly 13 times of pure CdS.On the basis of the results from SEM studies and our analysis, a growth mechanism of flower-like CdS is proposed by capturing the shape evolution.The imidazole ring of L-Histidine captures the Cd ions from the solution, and prevents the growth of the CdS nanoparticles.

View Article: PubMed Central - PubMed

Affiliation: College of Chemistry and Chemical Engineering, Northwest Normal University, Key Laboratory of Eco-Environment-Related Polymer Materials, Ministry of Education of China, Key Laboratory of Gansu Polymer Materials, Lanzhou 730070, China.

ABSTRACT
Morphology-controlled synthesis of CdS can significantly enhance the efficiency of its photocatalytic hydrogen production. In this study, a novel three-dimensional (3D) flower-like CdS is synthesized via a facile template-free hydrothermal process using Cd(NO3)2•4H2O and thiourea as precursors and L-Histidine as a chelating agent. The morphology, crystal phase, and photoelectrochemical performance of the flower-like CdS and pure CdS nanocrystals are carefully investigated via various characterizations. Superior photocatalytic activity relative to that of pure CdS is observed on the flower-like CdS photocatalyst under visible light irradiation, which is nearly 13 times of pure CdS. On the basis of the results from SEM studies and our analysis, a growth mechanism of flower-like CdS is proposed by capturing the shape evolution. The imidazole ring of L-Histidine captures the Cd ions from the solution, and prevents the growth of the CdS nanoparticles. Furthermore, the photocatalytic contrast experiments illustrate that the as-synthesized flower-like CdS with L-Histidine is more stable than CdS without L-Histidine in the hydrogen generation.

No MeSH data available.