1. Preparation of 4-Nitrophenol Solution Mixed with Sodium Borohydride

1. Weigh 14 mg of 4-nitrophenol and dissolve in 10 mL of DI water in a glass vial.
2. Weigh 57 mg of sodium borohydride and dissolve in 15 mL of DI water.
3. Mix the two solutions and magnetic stir for 30 min at room temperature to a uniform solution. Lab coat, safety goggle and gloves are needed as standard protocol protection.

2. Preparation of Catalyst Solution

1. Weigh 10 mg of palladium on active carbon and palladium on granular carbon respectively. Weigh 10 mg of active carbon as control group.
2. Transfer weighed catalysts to a vial and add 100 mL of DI water to each vial.
3. Sonicate the vials with an output power of 135 W for 10 min until catalysts are well distributed in water.

3. Catalytic Reduction of 4-Nitrophenol

1. Measure 1.15 mL of prepared 4-nitrophenol and sodium borohydride solution, transfer to a 5-mL glass vial.
2. Record the color of solution in the vial, wait 10 min and record if there is any change in the color of solution.
3. Add 1 mL of prepared palladium on active carbon catalyst solution to the vial, shake the vial by hand for 20 s. Observe reaction for 20 min, record when solution color starts to change and when solution color completely fades to transparent.
4. Repeat same procedure with the palladium on granular carbon catalyst solution.
5. Repeat same procedure with the active carbon catalyst solution.
6. Compare the color change between three catalysts after 0, 5, 10, 15, and 20 min of reaction time. To quantify this change, measure UV-Vis spectra of the sample during the 20 min reaction interval.