Preparation,characterization And Photocatalytic Performance Of TiO₂ Based Photocatalysts For Hydrogen Evolution

Recently,there is a growing interest in photocatalytic water splitting using solar energy because hydrogen is widely accepted as an alternative green energy resource.As one of the most extensively investigated photocatalysts,TiO₂ has advantages including long-term stability,nontoxic,and low cost.However,poor hydrogen generation efficiency is usually observed on pure TiO₂ due to fast recombination of photogenerated electrons and holes and backward reactions of intermediate products.In this work,Cu nanoparticles are used as co-catalysts to reduce the recombination of photogenerated charges and promote the following surface reactions,and the Cu-cluster-size dependent photocatalytic activity is investigated by varying the size of Cu clusters without changing Cu loading amount.TiO₂?B?/anatase heterojunctions are prepared to explore the effect of phase compositions on photocatalytic activity of the heterojunctions.The main contents are as follows:Cu nanoparticles less than 5 nm are successfully decorated on TiO₂ surface in this work by an easy and mild milling process.These Cu nanoparticles are highly dispersed on TiO₂ when the loading amount of Cu is no more than 10 wt%.The sizes of Cu nanoparticles can be controlled by changing the milling environment and decrease in the order of Cu-ethanol>Cu-water>Cu nanoparticles obtained through drying milling.The highest and stable hydrogen generation can be realized on Cu/TiO₂ with 2.0 wt%Cu and sizes of Cu nanoparticles ranging from 2-4 nm,in which high and stable photocurrent confirms promoted photogenerated charge separation.Smaller Cu clusters are demonstrated to be detrimental to hydrogen evolution at same Cu content.High loading of Cu nanoparticles of 2-4 nm will benefit photogenerated electron-hole recombination and thus decrease the activity of Cu/TiO₂.The results here demonstrate the key roles of Cu cluster size in addition to Cu coverage on photocatalytic activity of Cu/TiO₂ composite photocatalysts.2D TiO₂?B?nanomaterials are synthesized by a solvothermal method,in which TiCl₄and ethylene glycolate are used as the precursors.These nanosheets are loaded with Pt nanoparticles by photoreduction method followed by heating at different temperatures to remove surface-binding ethylene glycolate and acquire TiO₂?B?/anatase heterojunctions.Raman and XRD results demonstrate more and more anatase forms as the temperature increases.The phase composition in TiO₂ nanomaterials has great effect on their photocatalytic activity.The TiO₂?B?/anatase heterojunctions prepared at 400�C exhibit the highest activity with hydrogen generation rate of 33.79 mmol?g^-1?h^-1,much higher than that of pure TiO2?B?or anatase.