All of the solutions were prepared using Millipore Milli-Q water (resistivity > 18.2 MΩ−1) and total organics was lower than 3 ppb. An electrochemical workstation (CH Instrument series) was used to carry out all the electrochemical measurements. All the experiments were conducted at room temperature (∼23 °C) and under N2-atmosphere in a conventional three-electrode cell.