Study On The Syntheses, Modification And Photocatalytic Hydrogen Evolution Performance Of Titanate Photocatalysts

Since the21st century, the energy issue has been a main and urgent problemthat human beings are facing. Compared with the traditional non-renewable energysources (such as oil, coal, natural gas), the hydrogen has been identified as the cleanenergy because of its high calorific value, non-toxic, non-polluting and many otheradvantages. Photocatalytic water splitting to produce H2using the renewable solarenergy has been considered to the most ideal way to solving the energy crisis. In thispaper, we used hydrothermal-gel method, solvothermal method and sol-gel methodto synthesize a series doped titanate photocatalytic materials, and coupled them withthe CdS semiconductor photocatalyst to form the heterostructured semiconductorphotocatalysts. XRD, UV-Vis, SEM and TEM were used to characterize thesynthesized photocatalysts.BaTiO3can not as a photocatalyst to produce H2because the bottom of theconduction band (CB) is more positive than the reduction potential of H+/H2(0V vs. NHE). In this paper, BaxZn1-xTiO3and BaxSr1-xTiO3solid solutionphotocatalysts have been synthesized by hydrothermal-gel method and solvothermalmethod, respectively. Among them the Ba2+of the BaTiO3were partially replacedby Zn2+and Sr2+respectively. Under the irradiation of simulated solar light (320nm≤λ≤780nm), all of them produce hydrogen through water splitting, indicatedthat the partial substitution of Ba2+with Zn2+or Sr2+can control the band structureof the BaTiO3. Among them, the Ba0.9Zn0.1TiO3and Ba0.4Sr0.6TiO3have the bestphotocatalytic activity, the rate of hydrogen evolution were about364.1μmol·h-1·g-1and388.4μmol·h-1·g-1, respectively, under the irradiation of simulated solarlight（320nm≤λ≤780nm）using Na2S/Na2SO3(Na2S0.35M, Na2SO30.25M) assacrificial reagent. After loaded with CdS, the photocatalytic activity ofBaxZn1-xTiO3and BaxSr1-xTiO3can be improved significantly, among which the20%CdS/Ba0.9Zn0.1TiO3and40%CdS/Ba0.4Sr0.6TiO3show the best bestphotocatalytic activity. Their rate of hydrogen evolution were about1473μmol·h-1·g-1and1816μmol·h-1·g-1, respectively, under the irradiation of simulatedsolar light（320nm≤λ≤780nm）using Na2S/Na2SO3(Na2S0.35M, Na2SO30.25 M) as sacrificial reagent.Although SrTiO3can function as photocatalyst for hydrogen production fromwater splitting, but the photocatalytic activity was limited in the absence of preciousmetals. In this paper, the SrxZn1-xTiO3was synthesized by sol-gel method, amongwhich the Sr2+were partially replaced by Zn2+. Under the irradiation of simulatedsolar light (320nm≤λ≤780nm), the photocatalytic activity of the SrxZn1-xTiO3were higher then that of SrTiO3, indicating that the band structure of the SrTiO3was controlled by the doped of Zn2+. Among them, the Sr0.8Zn0.2TiO3shows thebest photocatalytic activity and the rate of hydrogen evolution was about696.5μmol·h-1·g-1under the irradiation of simulated solar light （320nm≤λ≤780nm）using Na2S/Na2SO3(Na2S0.35M, Na2SO30.25M) as sacrificial reagent. Afterloaded with CdS, the photocatalytic activity of SrxZn1-xTiO3can be improvedsignificantly. The10%CdS/Sr0.8Zn0.2TiO3shows the best photocatalytic activity, andthe rate of hydrogen evolution were about1969.5μmol·h-1·g-1under the irradiationof simulated solar light（320nm≤λ≤780nm）using Na2S/Na2SO3(Na2S0.35M,Na2SO30.25M) as sacrificial reagent.