CuO-SiO_(2)气凝胶@TiO_(2)纳米纤维无牺牲剂光催化还原CO_(2)

CuO-SiO_(2) aerogel@TiO_(2) nanofibers photocatalyzing reduction of CO_(2) without sacrificial agent

采用溶胶-凝胶法制备CuO-SiO_(2)复合气凝胶,通过在气凝胶孔道内填充TiCl4,然后将其气相水解,得到了在CuO-SiO_(2)气凝胶表面生长了高结晶度的TiO_(2)纳米纤维(CuO-SiO_(2)@TiO_(2)),纤维直径~16 nm。通过XPS、UPS、UV-Vis DRS、荧光光谱(PL)等表征了材料的结构及光电性能。结果表明,制备的CuO-SiO_(2)@TiO_(2)对可见光有明显吸收,且荧光强度较商用Ti O_(2)(P25)大幅降低,光生电子-空穴对更加稳定。再在纳米纤维上负载CuO,所得CuO-SiO_(2)@TiO_(2)/CuO在可见光区的荧光强度进一步增强。以300W氙灯为光源,分别以CuO-SiO_(2)@TiO_(2)及CuO-SiO_(2)@Ti O_(2)/CuO为催化剂,无牺牲剂条件下光催化还原CO_(2),4 h后甲醇产率分别为1304.0及1589.0μmol/g-cat,转换频率(TOF)分别为0.038及0.046 h^(–1)。循环实验表明,纳米纤维具有较好的光催化稳定性,经过4次光催化循环实验后,CuO-SiO_(2)@TiO_(2)/CuO的保留率~94%,甲醇产率可达1472.0μmol/g-cat,TOF为0.042 h^(–1)。

CuO-SiO_(2) composite aerogel was prepared by sol-gel method and then TiCl4 was filled in the channel of composite aerogel. TiO_(2) nanofibers growth on the surface of CuO-SiO_(2)(CuO-SiO_(2)@TiO_(2)) with high crystallinity were obtained with a diameter of about 16 nm by hydrolyzing TiCl4 in gas phase. The structure and photoelectric properties of the materials were characterized by XPS, UPS, UV-Vis DRS and PL. The results showed that compared with the commercial TiO_(2) nanoparticles(P25), the prepared CuO-SiO_(2)@TiO_(2) nanofibers had much lower fluorescence intensity and slower recombination rate of photogenerated election-hole pairs. CuO was loaded onto the CuO-SiO_(2)@Ti O_(2) nanofibers to obtain CuO-SiO_(2)@TiO_(2)/CuO nanofibers. The fluorescence intensity of the CuO-SiO_(2)@TiO_(2)/CuO was further increased. Photocatalytic reduction of CO_(2) was carried out in the absence of sacrificial agent using a 300 W xenon lamp as light source for 4 h. CuO-SiO_(2)@TiO_(2) and CuO-SiO_(2)@TiO_(2)/CuO were used as photocatalysts, the corresponding methanol yield was 1304.0 and 1589.0 μmol/g-cat. Turnover frequency(TOF) was 0.038 and 0.046 h^(–1), respectively. The cyclic experiments indicated that the nanofibers had good photocatalytic stability. After 4 cycles, the retention rate of Cu O-SiO_(2)@TiO_(2)/CuO was ~94%, and the methanol yield was 1472.0 μmol/g-cat, TOF was 0.042 h^(–1).