Preparation And Photocatalytic Properties Of Quantum Well SrTiO₃

Semiconductor photocatalysis is a new environment-friendly technology for environmental purification and energy shortage.SrTiO3 has great potential in photocatalysis as a typical n-type oxide semiconductor because of its high catalytic activity,corrosion resistance and chemical stability.However,the photocatalytic properties of SrTiO3 are severely limited by some common problems,such as wide band gap,low utilization of light energy and low efficiency of photoelectron and hole separation.In this work,we demonstrate a new strategy to efficiently separate electron-hole pair for high performance photocatalyst.For the first time,nano-quantum well is successfully fabricated through Nb surface doping of SrTiO3 nanocubes forming core-shell structure.1.In this work,nanoscale quantum well was successfully synthesized through Nb surface doping of SrTiO3 nanocubes.Using La3+ instead of Sr2+ to improve the carrier concentration without changing the.energy band structure of SrTiO3,the energy of the surface layer of SrTiO3 is reduced by substitution of Nb5+ for Ti4+ to form the Nb doped two-dimensional interface.Thus,the energy of surface layer of SrTiO3 will lower about 0.1 eV than inner,which will enable the carrier to move only through the surface layer,and thus quantum well effect of nanoscale is obtained.2.The quantum well particles demonstrated extraordinary photocatalytic degradation of Rhodamine（Rh B）under visible light in terms of decomposing organic pollutant,high stability and recyclability.The optimum photocatalytic performance（0.3 min-1）with Nb 5%surface doping and La 10%core doping SrTiO3 was much higher than those of pure SrTiO3（0.01 min-1）and the truncated La-SrTiO3（0.13 min-1）.The quantum confinement effect of surface Nb doping induced the generation of more ·O2-species which dominantly enhanced the photocatalytic degradation.3.In this work,the performance of H2 production over QW-SrTiO3 photocatalytic was also investigated.The highest photocatalytic activity of the sample with La 1%core doping and Nb 5%surface doping STO was shown with H2-production rate as high as 673.8 μmol h-1g-1,which is about 3.6 times higher than pure STO（188 μmol h-1 g-1）.In addition,the high photocatalytic activity was still maintained at low methanol content（5 mL）,this indicates that the design of quantum well on SrTiO3 surface is beneficial to the separation of photogenerated carriers.4.In this work,the QW-SrTiO3/GR composites were prepared based on the synthesis of QW-SrTiO3 nanoscubes.These QW,SrTiO3/GR composites gave excellent photocatalytic performance for H2-production under visible light irradiation.The optimum content of graphene was found to be 1.0 wt%,showing the highest H2 production rate of 14693.07 μmol h-1g-1,which up to～78 and～22 times higher than that of pure SrTiO3 and Nb-LaSrTiO3.The significant improvement in photocatalytic performance of QW-SrTiO3/GR composites is due to the potential of graphene/graphene-（-0.08 V vs.SHE）lower than Nb-SrTiO3,but higher than the reduction potential of H+/H2（0 V vs.SHE）.The graphene compounded with the QW-SrTiO3 can accept and transfer the photogenerated electrons rapidly from the QW-SrTiO3 surface to separate photogenerated electrons-holes,which promotes the separation of photogenerated electrons and holes and increases the absorption of visible light,and further more improves the rate of photocatalytic H₂-production.