吸附模式对有机物光催化降解的影响2.H-酸在TiO_2表面的光催化降解途径

EFFECT OF ADSORPTION MODES ON THE PHOTOCATALYTIC DEGRADATION OF ORGANIC MATTERS 2. PHOTOCATALYTIC DEGRADATION PATHWAYSOF H-ACID ON TiO_ 2

水溶液中H酸通过磺酸基团吸附在TiO2表面,UV照射TiO2所产生的自由基首先进攻吸附在TiO表面的磺酸基团,从而进一步导致萘环开环.pH2.5条件下,虽然饱和吸附量较大,但由于H酸仅通过一个磺酸基团吸附在TiO2表面,过程中产生的硫酸根速率较慢,最终的光降解速率也较慢.pH5.0条件下虽然饱和吸附量较小,但由于吸附在TiO2表面的两个磺酸基团同时受到来自TiO2表面自由基的进攻,过程中产生的硫酸根速率较快,最终的光降解速率也较快.吸附模式的差异是导致H酸在不同pH值条件下光催化降解途径和速率差异的关键因素.

H-acid adsorbed onto TiO2 surface by sulphonic groups, which were first attacked by free radicals of OHads followed by the cleavage of the naphthalene rings during the photo-degradation of H-acid on TiO2 surfaces. At pH 2.5, H-acid adsorbed onto TiO2 surface by one sulphonic group, which lead to a higher adsorption capacity but weaker adsorption bonds. Photo-degradation rates under this condition were therefore slower than at pH 5. O. At pH 5.0, H-acid adsorbed onto TiO2 surface by two sulphonic groups, which had a lower adsorption capacity but stronger adsorption bonds. Photo-degradation rates were therefore faster, than at pH 2. 5. Different adsorption modes were the fundamental reason why the photocatalytic degradation pathways and degradation rates were different under different pH conditions