The electrochemical properties of an n-type phosphorus doped diamond (PDD) electrode were investigated and compared with a p-type boron doped diamond (BDD) electrode. The Mott-Schottky plots in 0.1 M HClO4 are reported and related to the energy band diagram of electrochemically pretreated BDD and PDD. These results revealed that the band position of anodically pretreated PDD corresponded to the one of anodically pretreated BDD. Moreover, it was found the flat-band potential of the anodically pretreated PDD decreased by ca. 1 V after cathodically pretreatment. The cyclic voltammetries for Ru (NH3)(6)(3+/2+) showed that electrochemical behaviors of PDD and BDD were entirely different in possible direction for charge transfer across the electrode-electrolyte inaterface. In addition, less n-type diodelike behavior was observed at the cathodically pretreated PDD than the anodically pretreated PDD. These results point out the importance of the surface chemistry controlled by electrochemical pretreatments. (C) 2015 Elsevier Ltd. All rights reserved.