Comparison of Activities and Selectivities of Microcrystalline and Nanocrystalline Boron-Doped Diamond Electrodes Toward Oxygen Evolution in NaCl Solutions at Near-Neutral pH
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2025-07-11 |
| Journal | ECS Meeting Abstracts |
| Authors | Olga Baturina, Tatyana I. Feygelson, Jonathan Levine-MIles, Grant C. Daniels, Bradford B. Pate |
Abstract
Section titled āAbstractāThis paper reports on progress in the development of electrocatalysts intended for use in seawater that favor the oxygen evolution reaction (OER) over the competing chloride oxidation reaction (CER). Although boron-doped diamond (BDD) electrodes demonstrate low activity toward the OER due to a weak adsorption of water molecules, they attract attention due to their extreme durability at high current densities. Selectivity of BDD electrodes toward the OER in the presence of chloride ions at near-neutral pH has been largely unexplored. Among other factors, activities and selectivities of BDD electrodes are affected by the surface morphology, the grain size, surface composition, and boron doping level [1, 2] Herein, we compare activities and selectivities of the two BDD electrodes obtained under different diamond deposition conditions. Microcrystalline electrodes (MCD, free standing, 725 Āµm thick) were purchased from ElementSix, while nanocrystalline (NCD) 1.5 Āµm thick BDD films were produced at NRL by microwave plasma CVD deposition on molybdenum disk substrate. The boron doping level was 1.8 x10 20 and 9.5 x 10 20 at/cm 3 for MCD and NCD electrodes, respectively. Activities and selectivities of the MCD and NCD electrodes toward the OER and CER have been explored in synthetic ASTM seawater and 0.5M NaCl at pH 8.2. Figure 1 shows O 2 production efficiencies calculated for the OER+CER on MCD electrodes in solutions of 0.5M NaCl and synthetic seawater at pH 8.2. O 2 production efficiency was calculated as a ratio of the charge consumed for O 2 evolution to the total charge utilized during galvanostatic experiments at current densities of 1-100 mA/cm 2 for 10 min. An assumption was made that only O 2 and ClO - are generated. The charge consumed for the O 2 evolution was calculated by subtraction of the charge required for ClO - generation, from the total charge. Surprisingly, O 2 production efficiencies increase with current densities in both cases. We hypothesize that this may be due to generation of other ions such as ClO 3 - and ClO 4 - , which are not accounted for during O 2 production efficiency calculations. Experiments for detecting such ions using liquid chromatography coupled to mass-spectrometry are underway. The presentation will also discuss the reasons behind the dissimilar electrochemical performance of MCD and NCD electrodes. References [1] T.A. Ivandini, Y. Einaga, Chemical Communications, 53 (2017) 1338. [2] A. Kraft, International Journal of Electrochemical Science, 2 (2007) 355. Figure 1