The photocatalytic properties of CdS quantum dots (Q-dots)
and
Tb
3+
-doped CdS Q-dots dispersed in a borosilicate glass
matrix were investigated for the photodissociation of hydrogen sulfide
(H
2
S) into hydrogen (H
2
) gas and elemental sulfur
(S). The Q-dot-containing glass samples were fabricated using the
conventional melt-quench method and isothermal annealing between 550
and 600 °C for 6 h for controlling the growth of CdS and Tb
3+
-ion-doped CdS Q-dots. The structure, electronic band gap,
and spectroscopic properties of the Q-dots formed in the glass matrix
after annealing were analyzed using Raman and UV–visible spectroscopies,
X-ray powder diffraction, and transmission electron microscopy. With
increasing annealing temperature, the average size range of the Q-dots
increased, corresponding to the decrease of electronic band gap from
3.32 to 2.24 eV. For developing the model for photocatalytic energy
exchange, the excited state lifetime and photoluminescence emission
were investigated by exciting the CdS and Tb
3+
-doped CdS
quantum states with a 450 nm source. The results from the photoluminescence
and lifetime demonstrated that the Tb
3+
-CdS photodissociation
energy exchange is more efficient from the excited Q-dot states compared
to the CdS Q-dot glasses. Under natural sunlight, the hydrogen production
experiment was conducted, and an increase of 26.2% in hydrogen evolution
rate was observed from 0.02 wt % Tb
3+
-doped CdS (3867 μmol/h/0.5
g) heat-treated at 550 °C when compared to CdS Q-dot glass with
a similar heat treatment temperature (3064 μmol/h/0.5 g). Furthermore,
the photodegradation stability of 0.02 wt % Tb
3+
-CdS was
analyzed by reusing the catalyst glass powders four times with little
evidence of degradation.