4.2.1. Preparation of Ag/Ag2O

An amount of AgNO3 was dissolved in 50 mL of distilled water. The obtained solution was stirred for 30 min. Subsequently, 50 mL NaOH (0.2 M) was added dropwise. The resulting suspension was stirred for another 30 min to promote hydrolysis, and centrifuged, washed with distilled water three times, and dried at 70 ◦C for 24 h.

### 4.2.2. Preparation of TM Mixtures

The samples were obtained by mixing the self-prepared Ag2O with TiO2 at mass ratios of 4:1 (20 mass% TiO2), 1:1 (50 mass% TiO2), and 1:4 (20 mass% TiO2) with water. The suspensions were sonicated for 1.5 h and dried at 70 ◦C for 24 h. The Ag/Ag2O ⁄⁄ TiO2 with 20%, 50%, and 80% of TiO2 were nominated as TM 41, TM 11, and TM 14, respectively. For purpose of comparison, a TiO2 sample was prepared by the same procedure without the addition of Ag/Ag2O.

### 4.2.3. Preparation of TC Composites

The TC composites were prepared by a published precipitation method [25,29]. A measured amount of TiO2 was suspended in 50 mL of distilled water, and the calculated amount of AgNO3

corresponding to the desired mass ratio of Ag2O was added to the solution. The obtained suspension was stirred for 30 min. A volume of 50 mL 0.2 M NaOH was added dropwise. The resulting suspension was stirred for another 30 min to promote hydrolysis and centrifuged, washed with distilled water three times and dried at 70 ◦C for 24 h. The Ag/Ag2O ⁄⁄ TiO2 with 20 mass%, 50 mass%, and 80 mass% of TiO2 were denoted as TC 41, TC 11, and TC 14, respectively.
