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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.


The rate of H2 evolution on the samples CdS prepared without L-Histidine and with L-Histidine under visible light (a) Photoevolution of H2 on the photocatalysts under visible light irradiation (b).
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f8: The rate of H2 evolution on the samples CdS prepared without L-Histidine and with L-Histidine under visible light (a) Photoevolution of H2 on the photocatalysts under visible light irradiation (b).

Mentions: Figure 8a shows the photocatalytic activities of the samples for hydrogen generation under visible-light irradiation in an aqueous solution containing 0.5 M Na2S and 0.5 M Na2SO3 as the sacrificial reagents. Expectedly, for CdS with L-Histidine, the photocatalytic H2-production rate is markedly enhanced to 376.7 μmol/h, nearly 13 times of pure CdS (29.2 μmol/h). Because CdS with L-Histidine has a higher specific surface area and possesses more surface active sites and photocatalytic reaction centers, it exhibits a better photocatalytic performance to produce H2. Meanwhile, the photoelectrochemical and PL spectra validate that photo-generated electron-hole pairs of CdS with L-Histidine can be separated more efficiently than pure CdS. These behaviors are beneficial for photocatalytic performance to produce H2 and are the mainly reason for higher photocatalytic activity of flower-like CdS, while the detailed mechanism study still needs further investigations. Additionally, platinum (Pt), as an excellent co-catalyst, is loaded onto the CdS samples via a photodeposition method. The experimental result (seeing the Figure S2) shows that the photocatalytic H2-production rate of dendritic CdS decorated with 0.3% Pt is 53.1 μmol/h, while the flower-like CdS is 731.1 μmol/h, having a high photocatalytic activity for H2-production. In order to check the reproducibility of photocatalytic material and remove the dissolved gases, the reactor was evacuated and the photocatalytic experiment was repeated in every 5 h of reaction (Fig. 8b). The activity of CdS with L-Histidine is found to be almost the same in four repeated runs. The initial H2-production rate reaches 2001 μmol/h. In the next run, the rate of hydrogen evolution mildly declines. However, the hydrogen evolution rate still remains 1766 μmol/h in the fourth reaction run, but pure CdS almost does not produce H2 after 3 hours, suggesting that the CdS with L-Histidine is more stable than CdS without L-Histidine in the hydrogen generation, which is related to the structure of L-Histidine, the lone pair electrons of amidogen and hydroxy(-NH, -NH2 and -OH) in L-Histidine can draw the photogenerated holes of CdS, so the introduction of L-Histidine into the system can remove holes efficiently and avoid the photocorrosion problem of CdS. The slight decrease in the rate of hydrogen evolution might be related to the deactivation of the photocatalyst or attributed to the consumption of the sacrificial reagents in the solution36.


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)

The rate of H2 evolution on the samples CdS prepared without L-Histidine and with L-Histidine under visible light (a) Photoevolution of H2 on the photocatalysts under visible light irradiation (b).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f8: The rate of H2 evolution on the samples CdS prepared without L-Histidine and with L-Histidine under visible light (a) Photoevolution of H2 on the photocatalysts under visible light irradiation (b).
Mentions: Figure 8a shows the photocatalytic activities of the samples for hydrogen generation under visible-light irradiation in an aqueous solution containing 0.5 M Na2S and 0.5 M Na2SO3 as the sacrificial reagents. Expectedly, for CdS with L-Histidine, the photocatalytic H2-production rate is markedly enhanced to 376.7 μmol/h, nearly 13 times of pure CdS (29.2 μmol/h). Because CdS with L-Histidine has a higher specific surface area and possesses more surface active sites and photocatalytic reaction centers, it exhibits a better photocatalytic performance to produce H2. Meanwhile, the photoelectrochemical and PL spectra validate that photo-generated electron-hole pairs of CdS with L-Histidine can be separated more efficiently than pure CdS. These behaviors are beneficial for photocatalytic performance to produce H2 and are the mainly reason for higher photocatalytic activity of flower-like CdS, while the detailed mechanism study still needs further investigations. Additionally, platinum (Pt), as an excellent co-catalyst, is loaded onto the CdS samples via a photodeposition method. The experimental result (seeing the Figure S2) shows that the photocatalytic H2-production rate of dendritic CdS decorated with 0.3% Pt is 53.1 μmol/h, while the flower-like CdS is 731.1 μmol/h, having a high photocatalytic activity for H2-production. In order to check the reproducibility of photocatalytic material and remove the dissolved gases, the reactor was evacuated and the photocatalytic experiment was repeated in every 5 h of reaction (Fig. 8b). The activity of CdS with L-Histidine is found to be almost the same in four repeated runs. The initial H2-production rate reaches 2001 μmol/h. In the next run, the rate of hydrogen evolution mildly declines. However, the hydrogen evolution rate still remains 1766 μmol/h in the fourth reaction run, but pure CdS almost does not produce H2 after 3 hours, suggesting that the CdS with L-Histidine is more stable than CdS without L-Histidine in the hydrogen generation, which is related to the structure of L-Histidine, the lone pair electrons of amidogen and hydroxy(-NH, -NH2 and -OH) in L-Histidine can draw the photogenerated holes of CdS, so the introduction of L-Histidine into the system can remove holes efficiently and avoid the photocorrosion problem of CdS. The slight decrease in the rate of hydrogen evolution might be related to the deactivation of the photocatalyst or attributed to the consumption of the sacrificial reagents in the solution36.

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.