| The preparation of semiconductor photocatalysts, including TiO2 and SrTiO3, and their applications in photochargeable HSA electrodes have been investigated in this paper.At first, for the sol-gel method, the effects of the amount of acid catalyst, water and free alcohol in the solution on the time span from sol to gel have been studied, and the reasons have been explained as well. When the precursor was prepared by direct hydrolysis of Ti(OBun)4 without the addition of HNO3 then heat-treatment at 873 K for Ih, the as-prepared spherical TiO2 powder gives the relative uniform size distribution. The addition of HNO3 into solution can finally reduce the temperature of the phase transformation from anatase to rutile and shrink the temperature range of co-existence of two phases. The major factor determining the time span from sol to gel is the viscosity of the system, so the increase in the amount of water can increase the time span from sol to gel and the terminated temperature of phase transformation. The little difference of enthalpy between anatase and rutile phase makes the temperature of phase transformation unnoticeable.The experimental results showed that HSA electrodes mixed physically with TiO2 have no apparent photochargeable properties. The maximum discharge capacity of PHSA TOhd electrode is 14.6mAh/g at the discharge current of 6mA/g after photocharging for 6h, and the corresponding final photocharging potential is up to -0.89V(vs.Hg/HgO/6M KOH). Final photocharging potential of PHSA STO973 electrode after photocharging for 7h is up to -0.904V, and its first capacity is 5mAh/g at the discharge current of 6mA/g . The photocharging process can be explained by two kind of mechanisms, namely photoelectrocatalytic hydrogen storage mechanism and photocatalytic hydrogen storage mechanism. HSA electrodes modified with and SrTiO3 photocatalysts exhibit the obvious photochargeability. |
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