Preparation Of Oxide Semiconductor Nanomaterials And Their Photoelectrochemical Properties

With the rapid development of society,economy and science and technology,people's living standards have been greatly improved.But at the same time,the increasingly serious problems of environmental pollution and resource exhaustion also pose a great threat to the survival and development of human.In recent years,photocatalytic technology has developed rapidly,it can convert solar energy into electrical energy or chemical energy to alleviate energy crisis and achieve the degradation of pollutants.Semiconductors have been widely used in the fields of photocatalysis and photoluminescence due to its unique optoelectronic properties.Therefore,it is of great scientific significance to develop new semiconductor structures and explore their photoelectrochemical properties.In this paper,on the basis of two kinds of semiconductor materials,tungsten trioxide(WO3)and molybdenum trioxide(MoO3),semiconductors materials with special morphologies were synthesized.The morphology and structure of the semiconductor nanomaterials were characterized and analyzed in detail,and the related photoelectrochemical properties were also studied.The main research contents of this dissertation are as follows:1.Firstly,WO3 vertical nanosheet arrays were synthesized on conductive glass(FTO)by a first hydrothermal method,and the WO3/Bi2S3 nano-composite structure were constructed on WO3 by a secondary hydrothermal synthesis.The crystal structures and surface morphology of the samples were analyzed by X-ray diffraction(XRD),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).In addition,photoelectrochemical properties of WO3/Bi2S3 nano-composite structure prepared by this method were studied by a series of three-electrode system.Under light irradiation and 1.0 V bias voltage,the original WO3 photoelectrode have a photocurrent density of 0.42 mA cm-2,while the WO3/Bi2S3 composite photoelectrode have a photocurrent density of 4.68 mA cm-2.Therefore,compared with the original WO3 photoelectrode,the photocurrent of the composite photoelectrode increased about ten times.Then,the prepared materials were applied to photoanode-driven photoelectrochemical system for photoelectrocatalytic reduction of CO2.Reduction of CO2 to formic acid by photoelectrocatalysis,which confirmed the enhanced photoelectrocatalytic ability of the composited sample.The experimental results show that the WO3/Bi2S3 heterojunction constructed by hydrothermal method can promote the rapid separation of electrons-holes and reduce the recombination rate of electrons and holes.Therefore,it exhibits superior photoelectrochemical properties.2.Nitrogen-doped ?-MoO3 nanobelts were successfully prepared by a new simple one-step hydrothermal method.Different from the reported nitrogen doping methods,this preparation method can dope the nitrogen into the ?-MoO3 nanobelt while synthesizing the nanobelt.The surface morphology and crystal structure of the nanobelts were characterized,and the related electrochemical properties of the nanobelts were characterized as cathode materials of lithium ion batteries(LIBs).The experimental results show that the prepared nanobelts have obvious orthogonal structure and[001]growth direction.Then,the photoluminescence emission bands of the ?-MoO3 nanobelts at the center of-950 nm have been observed firstly.At a current density of 0.2 A g-1 and a voltage of 1.5 V,the initial discharge specific capacity of ?-MoO3 nanobelts electrodes reaches 240 mAh g-1,(the theoretical capacity is 280 mAh g-1).During the first cycle to the tenth cycle,the specific capacity of?-MoO3 nanobelts electrodes can maintain about 200 mAh g-1.The Coulomb efficiency increases gradually after the 20th cycle and reaches a high Coulomb efficiency of 99.9%in the 42th cycle.It indicates that the presence of N-dopant improves the electrical conductivity of ?-MoO3 nanobelts,and the synthesized?-MoO3 nanobelts have superior electrochemical energy storage capacity,which is a promising cathode material for LIBs.In addition,the obtained materials also have important application prospects in infrared optical devices.