CdS Quantum Dots in Hierarchical Mesoporous Silica Templated on Clay Nanotubes: Implications for Photocatalytic Hydrogen Production

Abstract

A scalable and efficient photocatalyst is a key factor for sustainable hydrogen production. For the first time, clay nanotube-templated mesoporous silica of MCM-41 type was used as an efficient carrier for photocatalytic nanoparticles. 4–5 nm CdS quantum dots (QDs) were synthesized in situ on the surface of this hierarchical aluminosilicate. The influence of the QD composition on the structural, spectral, and photocatalytic properties was investigated. A series of photocatalysts with various QD sizes (3.2–4.8 nm) and band gaps (2.46–2.66 eV) were obtained. Optimization of the CdS and cocatalyst (Ru) concentration resulted in an efficient visible light photocatalyst for hydrogen production. The photocatalytic activity was tested in an aqueous solution of Na2S/Na2SO3 under 30 W 450 nm diode illumination. The hydrogen evolution rate reached 2600 μmol/gcat·h (apparent quantum efficiency of 15%) for the system with 15.0 wt % of CdS doped with 0.2 wt % of Ru, which corresponds to the rate of hydrogen production of 17.1 mmol per hour counting on the active phase. The material demonstrated almost 100% efficiency of the catalytically active phase. It showed better catalytic activity in comparison to MCM-41 due to the hierarchical structure and presence of Al that stimulated electron transfer during the photocatalytic reaction.

Photoinduced Antibacterial Activity and Cytotoxicity of CdS Stabilized on Mesoporous Aluminosilicates and Silicates

“…Based on electron microscopy studies of CdS/MCM-41 as well as its spectral characteristics one might expect high possibility of electron-holes recombination due to close position of CdS nanoparticles and as a result decrease in photocatalytic activity. Previously it was shown that CdS/MCM-41 was less active in photocatalytic hydrogen generation under visible light compared to CdS/MCM-41/HNTs [ 21 ]. Here, this correlation was also observed.…”

“…All UV-Vis diffuse reflectance spectra had broad absorption region below 550 nm that is attributed to the charge transfer from the valence to the conduction band of CdS (Figure 5a). CdS band gap was determined by standard method by plotting (F(R) × hν) 2 for direct semiconductors versus hν, followed by linear extrapolation to intercept the energy axis [21]. Bang gap energy calculated using Tauc method equal to 2.36 eV for CdS/MCM-41 which is close to bulk CdS (2.4 eV), 2.45 eV for CdS/SBA-15, 2.47 eV for CdS/SBA-15-SH, 2.54 eV for CdS/MCM-41-HNTs and 2.58 eV for CdS/HNTs (Figure 5b).…”

“…Pharmaceutics 2022, 14, x FOR PEER REVIEW 9 of 14 was determined by standard method by plotting (F(R) × hν) 2 for direct semiconductors versus hν, followed by linear extrapolation to intercept the energy axis [21]. Bang gap energy calculated using Tauc method equal to 2.36 eV for CdS/MCM-41 which is close to bulk CdS (2.4 eV), 2.45 eV for CdS/SBA-15, 2.47 eV for CdS/SBA-15-SH, 2.54 eV for CdS/MCM-41-HNTs and 2.58 eV for CdS/HNTs (Figure 5b).…”

Antimicrobial Nanomaterials Based on Halloysite Clay Mineral: Research Advances and Outlook

“…By exploiting the different chemical composition and the different surface charges, HNTs can be modified, resulting in different nanomaterials with tunable properties that have found applications as fillers in polymeric matrices [ 17 , 18 , 19 ], drug carriers and delivery systems [ 20 , 21 ], supports for metal nanoparticles for catalytic purposes [ 22 , 23 , 24 , 25 ], and so on [ 26 , 27 ] ( Figure 5 a,b). The growing number of halloysite-related publications and patents attests to the clay’s growing popularity.…”

Heterogeneous Photocatalysis as a Potent Tool for Organic Synthesis: Cross-Dehydrogenative C–C Coupling of N-Heterocycles with Ethers Employing TiO2/N-Hydroxyphthalimide System under Visible Light

“…[ 1 , 8 ]. This situation is reflected in the comparatively low number of synthetic methods in fine organic synthesis based on heterogeneous photocatalytic systems compared to the mainstream applications of heterogeneous photocatalysis: oxidative destruction of pollutants [ 9 , 10 , 11 ], hydrogen generation [ 12 , 13 ], CO 2 reduction [ 14 , 15 , 16 ] and water splitting [ 17 ].…”