The regulation of H
2
evolution from formic
acid dehydrogenation
using recyclable photocatalyst films is an essential approach for
on-demand H
2
production. We have successfully generated
Au–Cu nanoalloys using a laser ablation method and deposited
them on TiO
2
photocatalyst films (Au
x
Cu
100–
x
/TiO
2
).
The Au–Cu/TiO
2
films were employed as photocatalysts
for H
2
production from formic acid dehydrogenation under
light-emitting diode (LED) irradiation (365 nm). The highest H
2
evolution rate for Au
20
Cu
80
/TiO
2
is archived to 62,500 μmol h
–1
g
–1
per photocatalyst weight. The remarkable performance
of Au
20
Cu
80
/TiO
2
may account for
the formation of Au-rich surfaces and the effect of Au alloying that
enables Cu to sustain the metallic form on its surface. The metallic
Au–Cu surface on TiO
2
is vital to supply the photoexcited
electrons of TiO
2
to its surface for H
2
evolution.
The rate-determining step (RDS) is identified as the reaction of a
surface-active species with protons. The results establish a practical
preparation of metal alloy deposited on photocatalyst films using
laser ablation to develop efficient photocatalysts.
ZnO is the most widely used as a catalyst material for photocatalytic application due to the suitable band gap energy and the chemical stability. It was reported by our previous study that the photocatalytic performance was significantly affected by the Ag content. In this study, ZnO-Ag nanocomposite materials have been successfully fabricated by flame pyrolysis and the effects of catalyst weight ranging from 2 to 10 mg on the photocatalytic performance were also investigated. Zinc acetate and silver nitrate were used as precursors for producing ZnO-Ag nanocomposites. The catalyst products, ZnO-Ag nanocomposite, were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). While, UV Vis spectrometry was used to measure the concentration of methylene blue (MB) before and after irradiations. Photocatalytic performances of nanocomposites were performed by evaluating the degradation of MB under UV and sunlight irradiations. The photocatalytic tests showed that the best performance was attained when the Ag content was 5 wt% and the weight of catalyst was as much as 10 mg after irradiation with sunlight, where the degradation rate of MB was 98% and the rate constant was 0.09/min.
Ag loading is known to enhance the photocatalytic performance of TiO2; however, the correlation between Ag and the resulting changes in TiO2 morphology and particle size is not well understood. A plasma-enhanced chemical vapor deposition (PECVD) and physical vapor deposition (PVD) were used to prepare Ag-TiO2 nanoparticulate thin films; the prepared films were annealed at 500 °C under N2 atmosphere. The Ag content was adjusted by the furnace temperature of the PVD system. Well-dispersed Ag nanoparticles on the surface of TiO2 nanoparticles were observed and analyzed using transmission electron microscopy (TEM). The morphology, particle size, and photocatalytic activity of the films were evidently affected by the Ag content. TEM images showed that the TiO2 nanoparticle size increased with increasing Ag content. Evaluation of the photocatalytic activity based on the degradation of methylene blue under ultraviolet (UV) light irradiation demonstrated that an Ag content of 2.2 wt% yielded the highest photocatalytic activity (5.5 times higher than that seen in a pristine TiO2 film). This fabrication method has advantages because it adds Ag in a more controlled manner compared to the liquid-phase methods. Furthermore, our fabrication method can provide a way to vary the Ag content while considering the relationship between the photocatalytic performance and the Ag content.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.