Electrode improvement using diamond-like carbon for electrochemical advanced oxidation in diuron degradation

Diuron is one of the pesticides. Its residual can contaminate natural water resource resulting in environmental and human health problems. Several processes have been used to remove diuron contamination. Nowadays, an electrochemical advanced oxidation process (EAOP) in a microchannel reactor is used to degrade diuron owing to its high efficiency. In this research, the diamond-like carbon (DLC) thin film was used as an electrochemical electrode because it has superior hardness and electrical conductivity. In this research, we have successfully synthesized the DLC thin films using graphite as target material on the surface of 304 stainless steel substrate by the direct current (dc) magnetron sputtering process. It was found that using the DLC thin film electrode caused less corrosion during the reaction when compared to the graphite electrode. The performance of diuron degradation depends on the properties of the thin film electrode, i.e., the sp2-to-sp3 ratio, the C-H bonds, and the C=O bonds. The DLC thin film electrode with the C=O bond led to the highest corrosion, up to 5.96 µg/h. The C-H bond in the DLC thin film improves the electrical conductivity (Rspecific = 0.076 Ω/nm) of electrode leading to high degradation performance, up to 70% within 100 seconds of residence time. Furthermore, each property of the DLC thin film results in different kind of intermediate during diuron decomposition.敌草隆（Diuron）是一种常用农药，其残留会污染天然水资源，进而引发环境问题与人体健康风险。目前已有多种工艺可用于去除敌草隆污染。近年来，微通道反应器内的电化学高级氧化工艺（EAOP）凭借高效性被应用于敌草隆的降解处理。本研究选用类金刚石碳（DLC）薄膜作为电化学电极，因其具备优异的硬度与导电性。本研究采用直流（dc）磁控溅射工艺，以石墨为靶材，在304不锈钢基底表面成功合成了DLC薄膜。实验结果表明，相较于石墨电极，使用DLC薄膜电极可显著降低反应过程中的腐蚀程度。敌草隆的降解性能取决于薄膜电极的多项关键特性，即sp²/sp³比例、碳氢键（C-H）与碳氧双键（C=O）。其中，带有碳氧双键的DLC薄膜电极腐蚀程度最高，可达5.96 µg/h。DLC薄膜中的碳氢键可提升电极的导电性（Rspecific=0.076 Ω/nm），进而实现优异的降解性能，在100秒停留时间内可达到70%的降解率。此外，DLC薄膜的不同特性会导致敌草隆降解过程中生成不同种类的中间产物。