TiO_2纳米管阵列覆盖Si薄膜光催化还原CO_2性能的研究

Photocatalytic Reduction of CO_2 over TiO_2 Nanotube Arrays Covered with Si Thin Film

本工作采用CVD法在阳极氧化TiO2纳米管阵列膜表面沉积一层非晶Si膜,通过退火后得到晶化了的Si膜/TiO2纳米管阵列的复合结构,并初步就其光催化还原CO2制备碳氢化合物的活性进行研究。拉曼光谱(Raman)、X射线衍射(XRD)、场发射扫描电镜(FE-SEM)、高分辨透射电子显微镜(TEM)等微结构表征结果表明所制备的TiO2纳米管阵列的厚度为270 nm左右,管直径约为70 nm,管壁厚度约为16 nm。覆盖的Si膜已晶化,其厚度约为300 nm。通过高效液相色谱(HPLC)及总有机碳(TOC)来检测光催化还原液相产物中的甲酸及总有机碳含量,发现负载Si膜后的TiO2纳米管阵列光催化性能有所提高,在装有400cut滤光片氙灯照射2 h下TOC含量从21.2 mg.L-1增长到29.5 mg.L-1,表明Si与TiO2的复合可有效的提高光催化还原CO2的活性,这可能与该异质结结构可增加对光的吸收并且可降低光生空穴-电子对复合有关。光催化循环实验表明所制得的催化剂在循环5次后仍可保持91.6%的催化活性。

In the current study,the composite structure of Si（thin film）/TiO 2（nanotube arrays） has been fabricated via annealing amorphous TiO 2（nanotube arrays,synthesized by anodizing titanium foil） on which was coated by Si film through chemical vapor deposition（CVD） method,and the photocatalytic reduction of CO 2 for hydrocarbon compounds（such like formic acid） conversion on as-prepared Si/TiO 2 structure has been initially investigated as well.The structure of Si/TiO 2 nanotube arrays was characterized by X-ray powder ray diffraction（XRD）,scanning electron microscopy（SEM）,Raman spectra（Raman） and transmission electron microscopy（TEM）.The length,diameter and wall thickness of as-prepared TiO 2 nanotube arrays were measured at about 270 nm,70 nm and 16 nm,respectively.The thickness of the crystallized Si film was tested at around 300 nm.The amount total organic carbon as well as formic acid produced in the liquid phase was detected by high performance liquid chromatography（HPLC） and total organic carbon analyzer（TOC）.It was found that the photocatalytic property was enhanced obviously after Si deposition.The TOC content increased from 21.2 mg·L-1 to 29.5 mg·L-1 under Xe lamp irradiation with 400 nm cut filter for 2 h.The improvement of photocatalystic property may due to the high light adsorption and low photogenerated electron and hole recombination of the heterojunction of Si and TiO 2.The photocatalytic circulating experiment shows that the photocatalyzer we prepared can keep 91.6% of its photocatalystic property after 5 times reaction.