阴极扫描法恢复三氧化钨光电化学水氧化性能及其机制

Recovery of photoelectrochemical water oxidation towards tungsten trioxide and its mechanism utilizing cathodic scanning process

三氧化钨(WO_(3))是典型的半导体材料,因其具有良好的光电化学(PEC)特性而受到了广泛的研究。但经电解后,WO_(3)光阳极会的PEC催化活性将出现急剧地衰减,导致其无法循环使用,造成了浪费。为了解决这一科学问题,实验以钨酸钠(Na_(2)WO_(4)·2H_(2)O)为钨源,HCl为酸源,通过沉淀法制备了WO_(3)粉体。然后,采用刮刀涂布工艺制备了涂层厚度约为15μm的WO_(3)/FTO电极。并采用X射线衍射(XRD)、拉曼光谱(Raman)、场发射扫描电子显微镜(FE-SEM)和X射线光电子能谱(XPS)等方法对其结构、形貌及组成进行表征。XRD和Raman结果表明,制备的WO_(3)具有单斜结构。通过FE-SEM观察发现,WO_(3)的表面形貌是由10~30 nm的纳米颗粒组成。PEC测试结果表明,电解前的WO_(3)/FTO电极在1.5 V vs.Ag/AgCl偏压作用下,可以产生7.7 mA/cm^(2)的饱和光电流,是同等条件下电解后WO_(3)/FTO电极的3.7倍(2.1 mA/cm^(2))。但经过阴极扫描后,可以使WO_(3)/FTO电极的饱和光电流恢复至8.1 mA/cm^(2),这与电解前相比,恢复率达105%。在对WO_(3)/FTO电极PEC性能恢复机制的研究过程中发现,WO_(3)表面O原子的结合状态是决定其PEC性能恢复的重要因素。

Tungsten trioxide(WO_(3))is a typical n-type semiconductor material,which has been widely investigated because of its good photoelectrochemical(PEC)performance.However,the PEC activity of WO_(3) photoanode will dramatically decrease after photoelectrolysis,resulting in its non-recycling and leading to waste.In order to solve this problem,WO_(3) powder is prepared by precipitation method using sodium tungstate(Na_(2)WO_(4)·2H_(2)O)as tungsten source and HCl as acid source.Then,the WO_(3)/FTO electrode with a coating thickness of ca.15μm is prepared by using a doctor-blade technique.The structure,morphology and composition of WO_(3) are characterized by X-ray diffraction(XRD),Raman spectroscopy(Raman),field emission scanning electron microscopy(FE-SEM)and X-ray photoelectron spectroscopy(XPS).XRD and Raman results show that WO_(3) could be attributed to monoclinic structure.FE-SEM images exhibit that the morphology of WO_(3) are composed of ca.10-30 nm nanoparticles.The PEC results indicate that the WO_(3)/FTO electrode before photoelectrolysis generates a photocurrent of 7.7 mA/cm^(2) at 1.5 V vs.Ag/AgCl,which is 3.7 times(2.1 mA/cm^(2))higher than that of the WO_(3)/FTO electrode after photoelectrolysis.However,the photocurrent of WO_(3)/FTO electrode can be recovered to 8.1 mA cm^(2),and the recovery rate is 105%after cathode scanning.During the process of exploring the PEC performance recovery mechanism of WO_(3)/FTO electrode,it is found that the binding state of O atoms on the surface of WO_(3) is an important factor to determine the PEC performance recovery.