Electrochemical sensing probe for chemical oxygen demand (COD) assay in waste water: molecular-scale particle design, electrode engineering and system integration

化学需氧量(COD)是完全分解水中有机化合物所需的氧化剂的量，对于净化饮用水中的危险和/或生物活性物质至关重要。传统上，这是通过将剧毒和腐蚀性消化器混合物中的有机污染物矿化来实现的，这会引起安全和环境问题。拟议中的发现拨款研究针对的是一种对有机污染物的氧化具有电化学、光电化学和热电化学反应的新型材料。因此，它们将被集成到一个无试剂的传感器系统中，该系统的性能可以超过现有的商业COD检测。这将通过应用其他引发和激活方法来实现，例如超声波、光、偏振和/或温度。这一发现计划将有三个互补的目标：(1)分子尺度的颗粒设计，提供针对多个氧化还原活性中心的高比表面积催化剂；(2)了解电化学-光化学-热释电催化对COD检测的协同作用；(3)集成了光、温度和超声波激发模式的传感器原型。*我们将首次引入氧化锌作为COD检测的催化阳极。与光催化方法类似，有机化合物将通过半导体的激发(光矿化)被氧化。在项目的后期阶段，将用金属团簇或金属氧化物(ZnO-Zu-Cu2O异质结)对氧化锌进行修饰，以启动可见光下的光电化学矿化。*第二个近期目标是采用全新的催化剂类别，如热释电LiNbO_3和LiTaO_3以及铁电BaTiO_3粉末和薄膜。原则上，这些材料的极性晶体结构表现出可以通过温差改变的自发极化。这会导致表面电荷的形成，而表面电荷又是热电化学活性的来源。在这一背景下，我们将合成热释电材料，并研究通过常规温度控制或应用超声波作为激发/激活工具的热激发对活性氧物种(羟基自由基)形成的影响。这些活性物种参与有机污染物的矿化。*每个阳极将在集成的光-超声-温度控制的电化学池中以安培、伏安和库仑传感模式进行验证。这将使我们能够研究：(I)电极动力学的基本原理，(Ii)用转盘电极伏安法研究的质量传输效应，(Iii)电极工程，以及(Iv)反应堆原型和系统集成。

The chemical oxygen demand (COD) is the amount of oxidant necessary to fully decompose organic compound in water and is critical for purifying drinking water from hazardous and/or biologically active substances. Conventionally this is carried out by mineralization of organic contaminants in the mixture of very toxic and corrosive digesters, which generate safety and environmental concerns. The proposed Discovery Grant research has been targeted at a new class of materials that have electrochemical, photo-electrochemical and pyro-electrochemical reactivity toward oxidation of organic pollutants. Thus they will be integrated into a reagent-free sensor system which can outperform the existing commercial COD assay. This will be accomplished by applying additional initiation and activation methods such as ultrasound, light, polarization and/or temperature. This Discovery program will have three complementary objectives: (1) molecular-scale particle design that delivers catalyst with a high surface area targeting multiple redox active centers, (2) understanding of the synergy electrochemical-photochemical-pyroelectric catalysis toward COD detection, and (3) the sensor prototyping with integrated excitation modes: light, temperature and ultrasound.***We will introduce for the first time ZnO as the catalytic anode for COD detection. Similar to the photocatalytic approach, the organic compounds will be oxidized through excitation of a semiconductor (photo mineralization). In the advanced phase of the project, the ZnO will be modified with metal clusters or metal oxide (ZnO-Zu-Cu2O heterojunctions) in order to initiate photo-electrochemical mineralization in visible light.***The second near-term objective is to adapt a completely new class of catalysts such as pyroelectric LiNbO3 and LiTaO3 and ferroelectric BaTiO3 powders and thin films. In principle, the polar crystal structures of these materials exhibit a spontaneous polarization that can be changed by temperature difference. This results in the formation of surface charges that, in turn, are the sources of pyro-electrochemical activity. In this context, we will synthesize pyroelectrics and investigate the impact of thermal excitation by conventional temperature control or by applying ultrasound as the excitation/activation tool, on the formation of reactive oxygen species (hydroxyl radicals). These reactive species participate in mineralization of organic contaminants.****Each anode will be validated in amperometric, voltammetric and coulometric sensing modes in the integrated a light-ultrasound-temperature-controlled electrochemical cell. This will allow us to examine: (i) fundamentals of electrode kinetic, (ii) mass transport effects studied by rotating disc electrode voltammetry, (iii) the electrode engineering, and (iv) the reactor prototyping and system integration.**