氟离子掺杂和吸附对二氧化钛光催化活性的影响

已有文献报道,在二氧化钛的体相和表面分别掺杂和吸附氟离子,都能加快水中有机化合物的光催化降解.前者归结于表面形成的三价钛离子促进光生载流子分离,后者归结于双电层中的氟离子促进羟基自由基脱附.但是,有关它们之间的活性差异未见有文献报道.本文采用水热法,以钛酸丁酯和氟化铵为原料,合成出具有不同氟离子掺杂量的光催化剂.通过苯酚降解反应,研究氟化钠和硝酸银外部加入对这些催化剂光催化性能的影响.结果表明:无论是处于二氧化钛的体相,还是处于二氧化钛的双电层外层和内层,这些氟离子都能促进苯酚的光催化降解.但是,它们的相对活性依次降低.此外,在催化剂的水悬浮液中,同时加入硝酸银和氟化钠,能进一步加快苯酚的光催化降解,且该反应的速率远远大于单独加入氟化钠或硝酸银时的速率总和.这说明将导带电子的还原过程和价带空穴的氧化过程耦合起来,是提高二氧化钛光催化量子效率的有效途径.

Effect of Fluoride Doping and Adsorption on the Photocatalytic Activity of TiO2

It has been reported that bulk doping or surface modification of TiO 2 with fluoride ions can enhance its photocatalytic activity for degradation of organic compounds in water.The effect of the former is ascribed to enhanced separation of photogenerated charge carriers through the surface-formed Ti 3+ species,whereas that of the latter is ascribed to enhanced desorption of hydroxyl radicals through the interfacial fluoride ions.However,the difference in activity between two modified catalysts has not been investigated.In this work,different fluoride-doped samples were hydrothermally prepared from butyl titanate and NH 4 F.Their photocatalytic activities after addition of NaF or AgNO 3 to the aqueous suspension were evaluated using phenol degradation as a model reaction.All the fluoride ions in the oxide lattices and in the outer and inner Helmholtz double layers of TiO 2 were positive to phenol degradation,but the magnitude of their influences followed a decreasing order.Moreover,phenol degradation in the presence of both NaF and AgNO 3 was much faster than the sum of their individual rates.These results indicate that combination of conduction band electron reduction and valence band hole oxidation is an effective way to improve the quantum yield of TiO 2 photocatalysis.