Synthesis Of Graphene/WO₃ Nanocatalysts And Their Photocatalytic Activities Under Visible Light

At this stage, solving environmental pollution and developing new types of clean, renewable energy are two major problems. To design and prepare photocatalysts with high activities for solar energy application is one of the most effective ways. In this paper, reduced graphene oxide/WO3 (rGO/WO3) composites are successfully synthesized via a modified one-step hydrothermal route. The morphology, structure and composition were characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared, X-ray photoelectron spectroscopy, thermo gravimetric analysisand and ultraviolet absorption spectrum respectively. Then their photocatalytic activities are examined by photodegradation of methylene blue solution (MB) and water splitting reaction for O2.The results show that graphite is successfully oxidized to graphene oxide (GO). GO is reduced to rGO and hexagonal WO3 particles grow on the surface of rGO through chemical action during the hydrothermal treatment. The addition of rGO is good for the growth of WO3 (001) plane. However, it also leads to the reunion of composites. As the ratio of rGO increases, their absorption abilities of visible-light increase firstly and then decrease. It is because doping a small amount of rGO can promote the separation of photo-generated electron (e-) and hole (h+). Nevertheless, excess rGO is likely shield the inner particles absorb photons.The photodegradation of methylene blue solution (MB) shows that photocatalytic activities of rGO/WO3 have a trend which increases firstly and then decreases as the ratio of rGO increases. Composites with 0.2 wt% rGO exhibit the best photocatalytic performance. It is because the addition of rGO can not only improve their MB absorptivities, but also enhance their absorption of photons which means more electrons are produced, e can transmit from WO3 to the surface of rGO rapidly through C-O-W bond. Then react with MB.The results of visible-light-drivcn photocatalytic water splitting show that doping a small amount of rGO (<0.2 wt%) can improve the stabilities of nanocomposites in alkaline solution. However, doping excess rGO (>0.2 wt%) can reduce their stabilities. The peak of oxygen production has a trend which increases firstly and then decreases as the ratio of rGO increases gradually. It is because the introduction of rGO can affect the concentration of OH- around the particles. A small amount of rGO (<0.2 wt%) can reduce the concentration of OH-, and a large amount of rGO (>0.2 wt%) can increase the concentration of OH-.