Paration And Photocatalytic Hydrogen Evolution Activities Of Catalysts Based On Ru-doped TiO₂

In recent years,due to the global energy crisis and environmental pollution,solar photocatalytic hydrogen production from water decomposition has become one of the most popular research topics.Semiconductor titanium dioxide has been widely used in the field of photocatalysis due to its good optoelectronic properties,green,pollution-free,high stability and low price.A large number of studies have proved that the photocatalytic performance can be effectively improved by metal doping and compounding with carbon materials.In this paper,a new type of ultrathin Ru-TiO₂nanosheets was obtained by introducing ruthenium ions into the lattice of ultrathin TiO₂nanosheets,which was then compounded with reduced graphene oxide（r GO）to obtain Ru-TiO₂/r GO composites,and their photocatalytic water splitting performance for hydrogen production was investigated.The details are as follows:First,ruthenium ions were successfully doped into ultrathin TiO₂nanosheet lattices by a one-step hydrothermal method,and a series of ultrathin X%Ru-TiO₂（X=2,5,7,9）nanosheets with different ruthenium doping contents were obtained.Their structures and morphologies were characterized in detail by various techniques such as solid-state UV-vis diffuse reflectance spectroscopy（DRS）,X-ray energy dispersive spectroscopy（EDX）,X-ray powder diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）,Atomic force microscopy（AFM）,Transmission electron microscopy（TEM）.Compared with pure TiO₂nanosheets,the shift of the characteristic peak positions in the XRD,Raman and XPS spectra of Ru-TiO₂nanosheets confirmed that Ru ions are successfully doped into the crystal lattice of TiO2,while the crystal form of TiO₂nanosheets did not change.UV-vis DRS showed that with the increase of ruthenium doping content,the absorption range of the nanosheets expanded from the ultraviolet region to the visible region,and covered the entire visible region.AFM confirmed that the thickness of X%Ru-TiO₂nanosheets was only 3-4 nm.The test results of photocatalytic hydrogen production showed that the catalytic activity of X%Ru-TiO₂nanosheets is significantly higher than that of pure TiO₂nanosheets,of which X%Ru-TiO₂nanosheets have the highest activity.After 6 hours of illumination,the hydrogen production is 43.7 mmol g^-1,about 215times than that of pure TiO₂.After recycling for three times,the catalytic activity does not decrease significantly,indicating that the catalyst has good stability.In addition,the screening experiment of electron sacrificial agent showed that the hydrogen production is the highest when triethanolamine is selected as electron sacrificial agent under the same experimental conditions.In order to further improve the catalytic activity,we mixed ultra-thin7%Ru-TiO₂nanosheets with reduced graphene oxide for hydrothermal reaction,and successfully prepared the composite Ru-TiO₂/r GO.The structure and morphology of the samples were characterized by XRD,Raman,IR,TEM and other test methods.Raman,IR and TEM tests confirmed the successful preparation of the composite Ru-TiO₂/r GO.XRD spectra showed that the introduction of r GO had no effect on the crystal form of Ru-TiO₂nanosheets.The photocurrent and impedance test results showed that the further modification of r GO significantly increased the photocurrent intensity and reduced the electron transfer resistance,indicating that the composite Ru-TiO₂/r GO had higher photoelectron transfer efficiency and improved the utilization of sunlight.The experimental results of photocatalytic hydrogen production showed that the catalytic activity of the composite Ru-TiO₂/r GO is 1.8times than that of Ru-TiO₂nanosheets.After 6 hours of illumination,the hydrogen production can reach 77.3 mmol g^-1,and the catalytic activity of the composite does not decrease significantly after recycling for three times,indicating that the composite has good stability.