| At present,the energy and environmental situation facing the world is quite severe.Photocatalytic technology utilizing solar energy has become a research hotspot and is widely used in photolysis of water,fuel cells,photoelectric detection,biomedicine,degradation of organic matter,lithium batteries and other fields.As the most widely used semiconductor catalyst in the field of photocatalysis,TiO2has the advantages of non-toxicity,low cost,suitable energy band structure,good chemical stability and good photostability.However,TiO2has a wide band gap energy（3.0-3.2 e V）and can only absorb ultraviolet light with a wavelength less than 380 nm,which greatly limits the development and utilization of solar energy.In addition,the photogenerated electrons and holes of pure TiO2are easy to recombine,which reduces the photoelectric conversion efficiency.Therefore,this paper aims at the problems of easy recombination of TiO2semiconductor photocarriers and low utilization rate of sunlight.By combining TiO2with narrow-band gap semiconductor,the absorption of visible light of semiconductor is improved.Meanwhile,the separation of photocarriers and interface charge transfer are improved by constructing interface heterojunction,so as to improve photoelectric conversion efficiency.The specific research work is as follows:1.Fully depleted double p-n heterojunction Cu2O/Ni（OH）2/TiO2for photocatalytic water splitting for hydrogen production.First,titanate nanotubes were prepared by hydrothermal method,and then TiO2nanorods were obtained by calcination at 400°C.Ni（OH）2nanoparticles were loaded on the surface of TiO2by chemical impregnation method.Finally,Cu2O nanoparticles were supported on Ni（OH）2/TiO2catalyst by ultrasonic-assisted glucose reduction method,and a double p-n heterojunction Cu2O/Ni（OH）2/TiO2semiconductor photocatalyst was obtained.The recombination of narrow-bandgap semiconductor Cu2O is used to improve the absorption of visible light.The completely depleted double P-N heterojunction formed at Ni（OH）2/TiO2and Cu2O/TiO2interface was used to improve the separation of photogenerated carriers and the interfacial charge transfer.The results show that the hydrogen production rate of Cu2O/Ni（OH）2/TiO2under UV-visible irradiation is up to6145μmol g-1h-1,which is 1.9 and 2.7 times that of single P-N heterobond Ni（OH）2/TiO2and Cu2O/TiO2,respectively.Under monochromatic light（λ=420 nm）,the apparent quantum yield of Cu2O/Ni（OH）2/TiO2is 20.2%.The results of 4 cycles of hydrogen generation for 5 h confirmed the high stability of the double P-N heterojunction photocatalyst.2.Ti/TiO2nanotube self-supporting electrodes for photo-assisted Li-CO2batteries.Amorphous TiO2nanotube arrays were prepared by anodizing method,and then TiO2nanotubes were obtained by calcination.TiO2nanotubes with different lengths were obtained by controlling the anodization time,and the effect of nanotube length on the performance of Li-CO2batteries was studied.By controlling the calcination temperature,TiO2nanotubes with different crystal types（anatase,rutile and mixed crystal phases）were obtained,and the effect of crystal type on the performance of Li-CO2batteries was studied.The results show that the mixed crystal TiO2anodized for 3 h exhibits the best battery cycle performance.The optimized Ti/TiO2electrode was used in the study of light assisted Li-CO2batteries.The battery performance under light and no light was compared.The results showed that the battery showed higher cycle（52 cycles）and lower charging voltage（3.3 V）compared with 10 cycle cycles and 4.75 V charging voltage under no light.This was due to the fact that TiO2photogenerated carrier effectively promoted electrode reaction kinetics and increased the reaction rates of CO2reduction（CDRR）and CO2precipitation（CDER）.Meanwhile,the semiconductor valence band can compensate the charging voltage,which can effectively reduce the CDER overpotential of the electrode and improve the cycle performance of the battery. |
