Abstract
Composite films of boron-doped nanocrystalline diamond and amorphous carbon (B-doped NCD/a-C) were prepared using a coaxial arc plasma deposition (CAPD) method at an unheated substrate temperature without using any reaction gases. Cyclic voltammetry (CV) measurements of the deposited films showed that they exhibit the unique electrochemical characteristics of diamond crystallites. The 4-nitrophenol (4-NP) aqueous solution, which is a recalcitrant substance found in industrial effluents, was degraded via electrolytic treatment using a batch-type system wherein the deposited films were used as anodes. UV–vis measurements revealed that part of the molecular structure of the 4-NP changed during this reaction. Furthermore, the total organic carbon (TOC) content in the 4-NP aqueous solution decreased as the electrolytic reaction progressed, implying that the degradation of 4-NP proceeded to yield CO2. The results reveal that the B-doped NCD/a-C films prepared using CAPD can be used as high-performance electrochemical electrode materials in industrial water treatment.
Highlights
Conductive polycrystalline diamond (PCD) films that are doped with impurities including boron (B) exhibit unique and advantageous chemical characteristics such as a wide potential window, extremely low background current, and high chemical stability in various solutions
The B-doped nanocrystalline diamond/amorphous carbon composite (NCD/a-C) films prepared by coaxial arc plasma deposition (CAPD) exhibited a wide potential window and an extremely low background current, which are fundamental electrochemical characteristics of conductive PCD electrodes and consistent with the measured Cyclic voltammetry (CV) characteristics of the PCD electrode in this study
The wide potential window observed in B-doped NCD/a-C films prepared by CAPD and conductive PCD electrodes can preferentially advance the redox reactions of various substances prior to the generation of oxygen and hydrogen by the electrolysis of water
Summary
Conductive polycrystalline diamond (PCD) films that are doped with impurities including boron (B) exhibit unique and advantageous chemical characteristics such as a wide potential window, extremely low background current, and high chemical stability in various solutions. They are expected to be useful as electrode materials in wastewater treatment to facilitate the degradation of the recalcitrant substances, such as phenolic pollutants [1]∼[4], which are difficult to degrade using electrochemical treatments via conventional noble-metal electrodes such as Pt elec-. Alternative methods without such limitations would accelerate the industrial application of diamond films in various fields.
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