Cathodic and anodic pre-treated boron doped diamond with different sp2 content: Morphological, structural, and impedance spectroscopy characterizations

Electrochemical impedance spectroscopy of polycrystalline boron doped diamond layers with hydrogen and oxygen terminated surface

“…Fig. 3 shows the equivalent circuit used for fitting the experimental data which takes into account the diffusion phenomena [15,20]. In this circuit the ohmic resistance R s of the electrolyte solution, electrodes, contacts etc.…”

“…The negative electron affinity (NEA) is a result of the C-H dipole at the hydrogenated diamond surface and the positive electron affinity (PEA) is caused by the C-O dipole at the oxygenated surface [5,[10][11][12]. The electrochemical properties of BDD with hydrogen or oxygen terminated surface have been studied by several authors [1,[11][12][13][14][15][16][17][18][19][20]. Electrochemical impedance spectroscopy (EIS) is a useful technique to study the double-layer structure and charge transfer at surface modified BDD films.…”

“…The impedance spectra can be fitted using equivalent circuits that correspond to the processes occurring at the electrolyte/BDD interface. The simplest equivalent circuit is the socalled Randles circuit, in which the Helmholtz capacitance and its corresponding parallel resistor [1,5,8,15,[21][22][23], as well as the Warburg element [15,20] are neglected. From the Mott-Schottky plots, obtained from EIS measurements, it is possible to determine the concentration of active acceptors (N A ) of BDD films.…”

“…Although there is a bulky literature about impedance spectra and Mott-Schottky plots on diamond electrodes, the subject is far from being fully understood and consistent. Individual experimental works show large spread of results, such as flatband potentials (which range from about 0 to 4 V vs. SHE) [1,17,20,[25][26][27][28] and also several different equivalent circuits were used for spectra fitting (see Fig. S1 in Supplementary data).…”

“…Denisenko et al [26] proposed a circuit with two RC elements in series, to account for a separation of space-charge layer and double layer at the interface. A replacement of simple capacitor with constant-phase element (CPE) and inclusion of Warburg impedance has been presented in several works [15,20,32]. A variant of Deniseko's model [26] with one CPE instead of capacitor was used in [21,22].…”