藉由TiO2半導體與氧氣進行光催化反應，分解有機及無機污染物，已成為今日環境何護的重要研究課題之一。由於TiO2在電解質溶液中所產生的界面能位偏移（Band Bending）致使TiO2與O2之間的異相電子傳遞(Heterogeneous Electron Transfer)速度遲滯，導致TiO2光解污染物速率降低。因此，若欲加速TiO2與O2之間的電子傳遞速度以提高TiO2催化活性，將有賴輔助催化劑的添加。
本實驗藉由固態與液態銅（Ⅱ）離子的添加，經由Sodium 2, 2-dichloropropionate分解速率分析，發現Cu（Ⅱ）離子及CuO確實可提高TiO2光催化活性；其中，Cu(II)離子濃度須小於10-4M，而CuO/TiO2則以0.4wt.%CuO/TiO2活性高。長時間活性測試顯示，於100小時內，0.4wt%CuO/TiO2活性並無明顯衰減。同時由Photochemical TiO2-slurry Cell Technique及薄膜TiO2/SnO2電極之電化學測試，發現Cu(Ⅱ)離子的輔助催化活性主要是在於增加TiO2/液相間電子傳遞速度。因此亦間接證明TiO2/液相間電子傳遞的快慢，可能是有機污染物光分解反應的速率決定步驟。

Photodegradation of chlorinated chemical waste was studied with CuO-modified TiO2. With bare powdered TiO2, the reaction was relatively sluggish; however, by modified with p-type powdered CuO, significant enhacement was observed. This photoactivity enhancement was investigated mechanistically with cyclic voltammetric and photochemical TiO2-slurry cell techniques, and bulk photolysis as well. Evidences showed that the electron injection from TiO2 surface to O2 was more affected than electron-up-taking by TiO2 from the sacrificial donor when CuO was incorporated, implying that the heterogeneous electron transfer from the illuminated ( 365 nm ) TiO2 to O2 be likely the rate-determing step. Photochemical TiO2-slurry cell techniques strongly supported such a conclusion. The photodegradation rate was found to reach the optimum condition as 0.4 wt.% of CuO was incorporated. Long-term stability tests showed that very little decay in photoactivity was observed with these CuO/TiO2 within 100 hours' consecutive photolysis. However, experiments showed that electron transfer from illuminated TiO2 to O2 might be deteriorated when large amount of chloride ion was present. This deterioration was tentatively ascribed to the blocking of electron capture of O2 by the specific adsorption of chloride ions at the TiO2 surface.