Boron-doped polycrystalline diamond films have been grown on molybdenum substrates by microwave-assisted chemical vapor deposition using a gas mixture of hydrogen and methane. AC impedance of diamond electrode was carried out in a solution of 0.5 M NaCl solution under various DC polarization conditions. Mott-Schottky plots were generated to determine the flatband potential of the boron-doped semiconducting diamond electrode in 0.5 M NaCl solution. It was found to be 0.91 +/- 0.2 V vs. R.E. in the frequency range of 1-400 Hz. The flatband potential was found to be higher than 0.91 V when the frequency was higher than 400 Hz and it was found to be lower than 0.91 V when the frequency was lower than 0.1 Hz. The kinetics were faster when a negative bias was applied to the diamond electrode as it was evidenced in the impedance data due to a reduction in the charge-transfer resistance.