2.4. Preparation of electrodes (การเตรียมอิเล็กโทรดรด)
The glassy carbon electrodes were mechanically polished using 0.3 μm alumina with double-distilled water on a porous surface. The electrodes were rinsed and sonicated for 15 min in double-distilled water. The three-electrode electrochemical cell was washed continuously with a 0.5 mol L−1HNO3solution.