Photoelectrochemical reduction of Carbon dioxide by metal-complexes-membrane electrodes

目的：光化学还原co2被认为是太阳能光化学转化和储存最有前途的方法之一。钌(II) -联吡啶配合物-甲基紫素(MV^<2+>) -三乙醇胺水系是CO_2的均匀光致敏还原体系之一。在这个系统中，三乙醇胺作为牺牲电子供体被耗尽。为了寻找一个循环体系，我们研究了在没有牺牲电子给体的情况下，用含有配合物和MV^<2+>的涂膜电极进行CO_2的光电还原。此外，还研究了悬浮TiO_2在液态CO_2和超临界CO_2中光催化还原CO_2的方法。结果:1。含有Ru (bpy)_3^<2+>和MV^<2+>的膜所覆盖的电极在-0.2 V以下形成了最大的光电流。这表明膜中的Ru (bpy)_3^<2+>和MV^<2+>体系产生光电流最有效。在Ru (bpy)_3^<2+>和MV^<2+>膜体系中，只发现II_2为还原产物。电极电沉积Pt或Ru，光电还原CO_2，生成丙二酸、乙酸和甲酸作为还原产物。结果表明，CO_2的还原过程分为两个阶段，即CO_2流体先被悬浮的TiO_2光催化还原，然后加水质子化生成甲酸。

Object : Phtochemical reduction of CO_2 is considered to be one of the most pro-mising approaches to photochemical conversion and storage of solar energy. An aqucous system of Ruthenium (II) -bipyridine complexes-methylviologen (MV^<2+>) -triethanolamine is one of homogeneous photosinsitized reductions of CO_2. In thissystem tricthanolamine is exhausted as sacrificial electron donor. With a view to search a cyclic system, we study on photoelectrochemical CO_2 reduction using coated membrane electrodes containing complexes and MV^<2+> without sacrificial clectron donor. Additionally photocatalytic reduction of CO_2 was studied using TiO_2 in suspension in liquid CO_2 and supercritical CO_2.Results :1.The electrode covered by the membranes containing Ru (bpy)_3^<2+> and MV^<2+> formed the largest photocurrent in the potential below -0.2 V.This indicates that Ru (bpy)_3^<2+> and MV^<2+> system in the membrane was most effective in generating photoc-urrent.2.In the Ru (bpy)_3^<2+> and MV^<2+> membrane system, exclusively II_2 was found as the reduction product. The electrode electrodeposited Pt or Ru reduced photoelectro-chemically CO_2 to produce malonic acid, acetic acid and formic acid as reduction products.3.We found that CO_2 was reduced by two stage reactions, that is, CO_2 fluid was photoc-atalytically reduced with TiO_2 in suspension and then protonated to formic acid by water addition.