Structure Design And Photoelectrocatalysis Properties Of One-dimensional Titanium Based Semiconductor Photoanode

Hydrogen energy has the advantages of clean and pollution-free,high combustion calorific value,storage,recyclability and wide application forms.At present,photoelectrocatalysis?PEC?water splitting to produce hydrogen using solar energy is one of the feasible methods for hydrogen production because is considered to be one of the most promising ways for hydrogen production.The core and key of photocatalysis is the research and development of high-efficiency photoelectrode materials.Studies have shown that Ti-based semiconductors,such as titanium dioxide?TiO₂?and titanates derived from TiO₂?such as SrTiO₃?,have become the most representative candidate materials for photoelectrodes due to their advantages of excellent chemical stability,suitable band structure,wide source of raw materials and low cost.However,the problem of low photoelectrocatalytic hydrogen production efficiency still restricts the development and application of titanium-based semiconductor photoelectrode materials.This is due to the wide bandgap,which lead to the weak light absorption ability and the short transmission distance of photogenerated carriers,which lead to the easy recombination of photogenerated electron-hole pairs and so on.In this paper,aiming at the key problems of the application of titanium-based semiconductors in the field of PEC,one-dimensional nanostructured TiO₂ and SrTiO₃ are studied,and their PEC properties are enhanced through fine structure optimization,non-metal doping,noble metal deposition,construction of heterojunction and their synergistic effects.Based on the work of this paper,the research results are as follows:?1?The controllable preparation and fine structure control of one dimensional TiO₂ photoanode materials.TiO₂ nanorod arrays were grown on fluorine-doped tin oxide?FTO?conductive glass substrates by hydrothermal method.Then,based on the TiO₂ nanorod arrays,branched rutile TiO₂ nanorod arrays were prepared by solution chemistry method,and rutile TiO₂ tapered nanotubes arrays were prepared by secondary hydrothermal etching method.The PEC performances of one-dimensional TiO₂ photoanode materials with three morphologies were studied.Test results showed that the photocurrent density of the TiO₂ tapered nanotube arrays can reach to 1.2 m A/cm² at 1.23 V vs.reversible hydrogen electrode?RHE?under simulated sunlight.The photocurrent densities of TiO₂ tapered nanotube arrays were 1.5 times higher than that of branched TiO₂ nanorod arrays?0.8 m A/cm²?and 3 times higher than that of pristine TiO₂ nanoarrays?0.4 m A/cm²?,respectively.The results showed that fine structural regulation of one-dimensional TiO₂ photoanode material can significantly improve its PEC performance.?2?The PEC properties of one-dimensional TiO₂ photoanode materials were improved by non-metallic element doping and noble metal deposition.On the basis of TiO₂ nanorod arrays by hydrothermal method,N-doped TiO₂ nanorod arrays were first prepared by calcination in NH3 atmosphere at high temperature,and then Au nanoparticles deposited N-doped TiO₂ nanorod arrays photoanode materials were obtained by magnetron sputtering.The results of PEC performance test showed that the photocurrent density of the N-doped TiO₂ nanorod arrays photoanode materials deposited by Au nanoparticles reached ².8 m A/cm² at 1.23 V vs.RHE under simulated sunlight,which was more than 7 times higher than that of pristine nanorod arrays.In addition,the photocurrent density of N-doped TiO₂ nanorod arrays deposited by Au nanoparticles could still maintain ⁹9% of the original under the long-term PEC reaction of 2 h,while the pristine TiO₂ nanorod arrays only maintained 71% of the original,indicating that its PEC stability had been greatly enhanced.The mechanism of PEC showed that N doping and modification of Au nanoparticles synergistically enhanced the light absorption of TiO₂ nanorod photoanodes.At the same time,Au nanoparticles provided hot electrons due to local surface plasmon resonance effect.The photogenerated carriers caused by the intrinsic absorption of the materials and hot electrons promoted the photoelectrochemical water splitting synergistically.?3?The PEC properties of one-dimensional TiO₂ photoanode materials were synergistically improved by carbon quantum dots?CQDs?modification and oxygen vacancies generated by hydrogen plasma treatment.On the basis of TiO₂ nanorod arrays by hydrothermal method,the TiO₂ nanorod arrays containing oxygen vacancies were first obtained by hydrogen plasma treatment,and then the CQDs modified hydrogenated TiO₂ nanorod arrays photoanode materials were prepared by surface modification of CQDs.The results of PEC performance test showed that the photocurrent density of the CQDs modified hydrogenated TiO₂ nanorod arrays photoanode materials were up to 3.0 m A/cm² at 1.23 V vs.RHE under simulated sunlight,which was 7.5 times higher than that of pristine nanorod arrays.In addition,its photocurrent density was higher than that of the hydrogenated TiO₂ photoanode materials reported in the literature.The mechanism showed that hydrogenation treatment could cause the formation of oxygen vacancies to suppress the recombination of photo-generated carriers.Meanwhile,the decorated CQDs could not only be used as the electron reservoirs to trap photo-generated electrons,but also remarkably enhanced the solar light harvesting due to their up-conversion effect.?4?The controllable preparation and fine structure control of one-dimensional SrTiO₃?STO?photoanode materials.The STO/STO homojunction photoanode materials were firstly prepared by means of spin coating and electrostatic spinning on FTO,and then STO/STO/Zn O homo/hetro junctions photoanode materials were obtained by atomic layer deposition?ALD?.The results of PEC performance test showed that the photocurrent density of STO nanofibers with engineered homo/hetro junctions was up to 309.8 ?A/cm² at 1.23 V vs.RHE under simulated sunlight,which was 600 times higher than that of pristine STO counterpart?0.5 ?A/cm²?.In addition,the photocurrent stability of the STO increased from 79.62% to 98% at 0.1 V vs.Ag/Ag Cl.The mechanism showed that the introduced STO film rendered the formation of STO/STO homojunction,which provided an extended contact area to enhance the electron-hole mobility across the interface.Meanwhile,the ALD-deposited Zn O allowed for the construction of STO/Zn O heterojunction,which could build up internal electric fields at the interface to hinder the recombination of electron-hole pairs,causing a totally enhanced photoelectrochemical?PEC?activity.