Photoelectrochemical Performance Of TiO₂ Nanorod Arrays Sensitized With PbS And CdS Quantum Dots

In the 21 st century,the extensive utilization of renewable energy sources is an important factor for the development of society.There is an effective solution: the solar power as a kind of renewable and sustainable energy source,can be used and turn into chemical energy.The photoelectrochemical?PEC?water splitting technology can splitting water into hydrogen and oxygen through semiconductor absorption light.Besides,TiO₂ has been used in the field of PEC water splitting as a kind of nontoxic,chemical stability,proper energy level?corresponding to water splitting energy level?and cheep semiconductor material.But since 1971,the research about TiO₂ for PEC water splitting has been lasting till now.The reason is that the energy gap of TiO₂ is large?3.0 eV for rutile,3.2 eV for anatase?,only making use of UV light?just containing about 4% of the solar power?.According to the shortcoming of TiO₂,we decorated TiO₂ nanorod arrays with metal sulfide with ability of visible light absorption response from broadening the region of solar light absorption and utilization in this manuscript.And we make an analysis of the mechanism of the enhanced PEC water splitting performance of the modified photoanodes.The context in this manuscript can be summarized as following:?1?We fabricated the TiO₂ nanorod arrays on the FTO glass through the hydrothermal method.Then we decorated the PbS quantum dots?QDs?and CdS QDs on the surface of TiO₂ nanorod through the successive ionic layer absorption and reaction process.Through this method,we can effectively broaden the region of light absorption and utilization and can improve the photocurrent density obviously.For example,when we sandwich the PbS QDs between the TiO₂ nanorod arrays and the CdS QDs,the photocurrent density of TiO₂/PbS/CdS is increased to 1.35 mA·cm-2 at 0.9716 V vs.RHE?0 V vs.Ag/AgCl?under 60 mW·cm-2 simulated sunlight.Whereas,the photocurrent density is 0.09 mA·cm-2 for TiO₂ and it is 0.72 mA·cm-2 for TiO₂/CdS under the same conditions.Besides,TiO₂/PbS/CdS shows the improved PEC water splitting stability.?2?The enhanced PEC water splitting performance for TiO₂/PbS/CdS can be attributed to the PbS QDs and CdS QDs broadening the region of sunlight absorption spectrum.At the same time,the total resistance?Rt?is 138 W·cm-2 for TiO₂/PbS/CdS,but it is 5651 W·cm-2 for TiO₂ and it is 233 W·cm-2 for TiO₂/CdS.The PEC water splitting stability of TiO₂/PbS/CdS comes from the valence band offset between PbS and CdS which causes a small energy barrier resulting into the holes facile transmission from the valence band of PbS to the valence band of CdS.Besides,its stronger radiative recombination can reduce the holes accumulation.According to the research in this manuscript,we can improve the PEC water splitting performance of TiO₂ nanorod arrays through broadening the the region of sunlight absorption and utilization spectrum by decorating the PbS QDs and CdS QDs on the surface of TiO₂ nanorod arrays.