Preparation And Electrochemical Properties Of Composites Compound With AB₃-type Hydrogen Storage Alloys And Photocatalyst

In this paper, AB3type hydrogen storage alloy La0.67Mg0.33Ni2.5Co0.5andLaMg2Ni2.7Co2.1Mn2.7Cu1.5were prepared by coprecipitation-reduction-diffusion method,photocatalyst TiO2powder was prepared by hydrothermal method. The structure andcomposition of hydrogen storage alloys and photocatalyst were analyzed by XRD. Thecombination electrodes of photocatalyst and hydrogen storage alloys were combined in twoways: mechanical mixing and surface smearing, and the electrochemical properties likeactivation property, max-discharge capacity and discharge capacity decline rate were studiedrespectively. Conclusions as followed:The activation properties and max-discharge capacities of combination electrodescombined in mechanical mixing were dramatic reduced with the increase of content ofphotocatalyst without the light, despite the increase of circulatory stabilities. Theelectrochemical properties were respectively increased with the light condition. The activationtime of the La0.67Mg0.33Ni2.5Co0.5combination electrodes mixed20%TiO2decreased one time,the max-discharge capacity increased11mAh/g and the decline rate lessened3.4%. Theactivation time of the LaMg2Ni2.7Co2.1Mn2.7Cu1.5combination electrodes mixed20%TiO2decreased one time, the max-discharge capacity increased14mAh/g and the decline ratelessened3.9%. All of these suggested that the light condition is helpful to the electrochemicalproperties of combination electrodes.Despite the increase of circulatory stabilities, the activation properties and mix-dischargecapacities of combination electrodes combined in surface smearing were decreased as theTiO2content increasing. Compared to the condition without light, electrochemical propertiesof combination electrodes were markedly improved, especially the max-discharge capacity. The max-discharge capacity of La0.67Mg0.33Ni2.5Co0.5combination electrodes smeared20%TiO2under the light condition was44mAh/g higher than without the light condition, and thedecline rate was5.1%lower. The max-discharge capacity of LaMg2Ni2.7Co2.1Mn2.7Cu1.5combination electrodes smeared20%TiO2under the light condition was37mAh/g higherthan without the light condition, and the decline rate was6.2%lower. Suggesting that surfacesmearing is a better way to combine hydrogen storage alloy and photocatalyst.In addition, the way how photocatalyst may work was analyzed tentatively through thediscussion of the surface smeared electrodes reaction process, which was believed that themost possibly way is charge transfer and hydrogen reduction effect caused byphotoelectron-hole—produced by photocatalyst by absorbing the energy from thelight—affecting the process of hydrogen absorption and desorption directly or indirectly.