Plasmon Enhanced TiO₂-based Catalysts For Photoelectrochemical Water Splitting

Hydrogen energy has become one of the most promising green clean energies due to its high calorific value and non-polluting combustion products.It is an effective and feasible method to fully utilize solar energy for photoelectrochemical water splitting（PEC）to produce hydrogen.The research and preparation of photoelectrode materials are critical to hydrogen production efficiency.At present,the efficiency of PEC water splitting is low,and the two major problems faced in the reaction system are as follows:first,the band gap is wide,resulting in a narrow light response range in the visible light region and thus low utilization of sunlight.Second,the severe phenomenon of carrier recombination and the low light conversion efficiency.Therefore,it is necessary to modify the catalysts to solve the above problems to improve the efficiency of PEC water splitting.In this paper,one-dimensional TiO₂ nanotube arrays（pristine TNTs）with a diameter of about 80 nm were prepared by anodizing in an ethylene glycol solution containing F^-.Then electrochemical reduction and the deposition of gold nanoparticles were carried out to construct homojunctions and extend light harvesting,respectively,and to simultaneously improve the ability of carrier separation and light absorption.The final composite with significantly enhanced photocurrent density was prepared by adjusting the time of electrochemical reduction and deposition of gold nanoparticles.The phase and morphological characterization results of XRD,SEM,TEM shows that anatase TiO₂ nanotubes modified with Au nanoparticles are successfully prepared in this experiment.XPS and UPS data confirms that O vacancy and Ti³⁺are successfully introduced into the samples（R-TNTs）reduced through electrochemical reduction.And the homojunction is formed between R-TNTs and pristine TNTs in R-TNTs material.The UV-visible absorption spectra shows that TiO₂ absorbed a little visible light after electrochemical reduction.However,there is obvious light absorption in the visible light region after depositing Au nanoparticles.The Mott-Schottky curves indicate that the carrier concentration of the sample R-TNTs(1.04×10²⁵ cm^-3)is 5 orders of magnitude higher than that of pristine TNTs(1.43×10²⁰ cm^-3),which means that electron-hole separation has been effectively enhanced.Finally,the results of electrochemical performance shows that the optimized sample Au@R-TNTs has a photocurrent density of 1.64 m A·cm^-2 under simulated sunlight,and the light energy conversion efficiency up to 0.55%,4-fold and 2-fold that of pristine TNTs,respectively.Therefore,the plasmonic Au nanoparticles modified TiO₂ nanotube arrays composites with homojunction structure prepared in this paper show excellent PEC performance,which provides a reference for the design and preparation of photoelectrochemical catalysts.