Characterization and photoelectrochemical performance of gold nanoparticles modified titanium dioxide nanotubes by pulse electrodeposition / Siti Sarah Ismail

Solar-energy conversion devices such as photoelectrochemical (PEC) cell is one of
the eco-friendly and cost effective ways that uses solar light as energy source to
convert solar energy into electricity. Titanium dioxide (TiO2) is one of the metal
oxides that is preferable used as photoanode in a PEC cell as it exhibits strong
photocatalytic activity low cost and stable in aqueous solution. However, the wide
band gap of TiO2 (3.2 eV) only allows it to be activated upon irradiation of
ultraviolet (UV) light. Therefore, in this study, TiO2 nanotubes decorated with gold
nanoparticles was used as substrate in order to determine the physicochemical
properties as well as the photoelectrochemical properties. The nanotubes were
fabricated via electrochemical anodization method and thereafter were loaded with
gold nanoparticles by pulse electrodeposition method. For the incorporation of gold
nanoparticles, several parameters were varied; applied deposition potential,
concentration of gold solution, deposition time and duty cycle. The gold
nanoparticles decorated TiO2 (AuTNT) were characterized using FESEM, EDX,
XRD and UVDRS. The quality of the film produced was tested with adhesion test
whereby the photoelectrochemical performance of AuTNT was evaluated with PEC
test to obtain AuTNT with extended light spectral response. The presence of gold on
nanotubes was confirmed from XRD analysis(44.8o and 65.6o respectively) and
further supported with EDX analysis(highest amount of Au detected is 4.11 w.t.%
for 1000μMAuTNT). This study revealed that the morphology of AuTNT was
influenced by the deposition potential and the amount of gold deposited increases
with increasing deposition time. The use of duty cycle for the synthesis of AuTNT
did not alter the sample morphology but instead affects the amount of gold. It was
found that 10% duty cycle with -0.7V applied potential, at 30 minutes deposition
time in 100μM gold solution is the optimum condition in fabrication AuTNT with
the highest PEC performance (efficiency,Ƞ = 0.80) and able to decrease the band
gap of TiO2 from 3.2 eV to 1.6 eV (47% reduction). Thus, AuTNT can be utilized as
photoanode in solar-energy conversion devices.