Controlled Preparation And Photoelectrochemical Water Splitting Performance Of Heterostructured Mesocrystalline TiO₂ Nanorod Arrays

With the progress of technology and the evolvement of mankind world,energy crises and environmental issues have caused widespread concern.To alleviate these problems,it is of necessity to find a renewable energy source that is highly efficient,clean and resource-rich.Photoelectrochemical（PEC）water splitting is a promising technology that relies on solar energy and electric fields rather than the requirement of the consumption of fossil fuels.Among many photoanode materials,titanium dioxide（TiO₂）has superiorities,such as inexpensiveness,non-toxic,outstanding biocompatibility,and suitable energy band structure.But its shortcomings exist with low absorption rate of visible light and high recombination rate of photogenerated electrons and holes,restricting the uses of TiO₂in photoelectric decomposition of water.Therefore,in order to improve the photoelectric catalytic performance of TiO₂,this work modified the defects of TiO₂by semiconductor compounding,introduction of promoters,and noble metal modification methods.The main research contents show as follows:（1）The mesocrystalline TiO₂nanorod arrays（TiO₂NAs）was compounded with calcium titanate（Ca TiO₃）via hydrothermal method,and the heterostructured mesocrystalline TiO₂-Ca TiO₃nanorod arrays was obtained.The morphology and structure of the heterostructured mesocrystalline TiO₂-Ca TiO₃nanorod arrays were explored via a series of characterizations.The results showed that the heterostructure was well-distributed grown on the F-doped Sn O₂（FTO）substrate,indicating the characteristics of core-shell structure along with the maintaining of a good mesocrystalline nanorod arrays structure.The results show that the photocurrent density of heterogeneous mesocrystalline TiO₂-Ca TiO₃nanorod arrays is 1.20 m A/cm²at the decomposition voltage of 1.23 V vs.RHE,which is 60%higher than that of unmodified TiO₂（0.75 m A/cm²）.The increase in TiO₂photocurrent density is attributed to the formation of heterojunctions,this construct schema made it available to reduce the recombination rate of photo-generated electrons and holes,promote the separation and transport of carriers,and eventually improve the photoelectric catalytic performance of TiO₂.（2）The composite structure of titanium dioxide-double layer metal hydroxide（TiO₂-Co Al LDH）was synthesized by electrochemical deposition.The morphology and structure of the composite structure of TiO₂-Co Al LDH were explored via a series of characterizations,and it was illustrated that Co Al LDH nanosheets were uniformly deposited on the mesocrystalline TiO₂nanorod arrays.The research results indicated that the decomposition voltage of TiO₂-Co Al LDH in the water was 1.23 V vs.RHE and the photocurrent density was 0.92 m A/cm²,which was 34%higher than that of unmodified TiO₂.The increase in the photocurrent density of TiO₂is attributed to the loading of Co Al LDH,which accelerates the oxidation of water and improves the surface injection efficiency,thereby improving the photoelectrochemical performance of TiO₂.Subsequently,the precious metal ruthenium（Ru）was loaded on the composite material via electrodeposition method to form a TiO₂-Co Al LDH-Ru ternary composite material.The photocurrent density reacheed 1.97 m A/cm²,which was nearly twice as high as that of unmodified TiO₂.Revealing the great potential of the TiO₂-Co Al LDH arrays and the excellent synergy among TiO_2-Co Al LDH-Ru.