Construction Of Amorphous-Transition-Metal-Oxides-Based Hetero-Nanotubes And Study On Their Photocatalytic Performance

Taking advantage of photocatalysis technology for pollutants degradation and hydrogen evolution through water splitting is one of the efficent methods to solve the energy and environmental problems.However,restricted by low quantum efficiency and other factors,photocatalytic materials are unable to be applied on a large scale.Therefore,the development of efficient semiconductor photocatalysts is a great challenge in condensed matter physics and other fields.As photocatalytic material,amorphous transition metal oxides（a-TMOs）possess high density suspension bonds and active sites,but they have disadvantages such as easy agglomeration,high photocarrier recombination rate and low visible light utilization efficiency.The construction of a-TMOs-based type-Ⅱ or Z-scheme heterojunction can effectively inhibit the electron-hole pair recombination rate and broaden the absorption range of visible light.In this paper,based on the supramolecular self-assembly,in situ growth and chelating-grafting synthetic strategy,type-Ⅱ and Z-scheme hetero-nanotubes are successfully constructed by exploiting the synergistic advantages of a-TMOs and graphitic carbon nitride（g-C₃N₄）.Their formation process,microstructure,photoelectrical properties,photocatalytic mechanism etc.are studied on details.The concrete contents are as follows:（1）The g-C₃N₄/a-CoO hetero-nanotubes were constructed by one-step annealing method after cobalt ions were anchored on the surface of the supramolecular precursor by intermolecular electrostatic attraction.This synthetic strategy can effectively solve the problems of easy agglomeration and oxidation of CoO during the preparation process.The photocatalytic performance can be significantly enhanced due to the large contact area of the two-dimensional components of g-C₃N₄/a-CoO heterojunction and the promotion on separation of photoexcited electrons and holes via the generated Co-N bonds.The optimized g-C₃N₄/a-CoO heterojunctions possessed the superior hydrogen evolution rate of 428.80μmol h^-1g^-1,which is 5.90times than that of pure CN.This work is helpful to promote the application of a-CoO in photocatalytic technique and the simple a-CoO-based hetero-nanotubes synthesis strategy will provide a theoretical basis for emerging applications in energy-related fields and beyond.（2）The 2D/2D/2D a-TMOs/C/g-C₃N₄triple-layered hetero-nanotubes were synthesized by utilizing the synthetic strategy of ethylenediaminetetraacetic acid（EDTA）chelating metal ions and simultaneously the chelates grafting onto the surfaces of the supramolecular precursors.The introduction of the appropriate amount of EDTA is benefit for the uniform dispersion of metal ions;and the formed high-conductivity carbon layers not only provide good protection for the material structure under high temperature etching,making the tubular morphology more regular and tidy,but also effectively improve the efficiency of carrier transportion and the charge kinetics then enhancing the photocatalytic activity.The obtained triple-layered hollow nanostructures have excellent photocatalytic performance,and the optimized a-ZnO/C/g-C₃N₄hetero-nanotube exhibits a high hydrogen evolution rate of 400.01μmol h^-1g^-1,outperforming that of bulk CN about 14.29 times.This eco-friendly synthetic strategy can provide a valuable reference for the construction of novel amorphous multicomponent heterojunctions with complex hollow micro/nanostructures in photo/electrocatalysis and energy-related fields.