Study On Novel Composite Electrodes Used For Anti-biofouling Of Underwater Window

Currently, mechanical scrapers and a “copper shutter” system based on copper corrosion mechanism have been used for antifouling of underwater optical sensors. However, both techniques can easily scratch the optical window and block the light path. Besides, the energy consumption and cost are also high. Researchers electrolyze seawater to prevent biofouling by using conductive indium tin oxide(ITO) glass electrode. However, the material has high overpotential for Cl2 evolution, the sustainability is short, and the antifouling effect is also limited. As a noble metal with excellent chemical stability and eletro-catalytic activity, Pt can be a candidate for chlorination. The purpose of this study is to grow nanoscale Pt as catalysts onto ITO electrode surface by constant current electrodeposition method, to reduce the potential of electrochemical chlorination and improve the longevity and sustainability of working electrode. Therefore, the biofouling of the optical window in underwater environment will be effectively prohibited.In this thesis, the electrocatalysis chlorination property of porous nickel, porous titanium, Ir-Ti, Ir-GC, Ir-CF, Ir-ITO anode electrodes were explored in preliminary work, but there was a problem of short work life and low oxidation current density. Therefore, Pt-ITO composite electrodes were prepared with the chronopotentiometry electrodeposition technique and they were characterized by scanning electron microscope(SEM) with energy dispersive spectrometer(EDS). The electrocatalysis chlorination property, longevity and sustainability of Pt-ITO were studied by means of LSV anodic polarization test and DC electrolysis technique. Antifouling capability of Pt-ITO in diatom suspension was studied by means of UV test and optical microscope.Some innovative achievements have been summarized as follows:(1) Pt-ITO composite electrodes were prepared with the chronopotentiometry electrodeposition technique. The effect of applied current density and electrolytic deposition time on electrodeposition was analyzed from the thermodynamics perspective. The SEM and EDS analysis showed that nano-scale Pt is formed on ITO surface in small particles states.(2) The electrocatalysis chlorination property of Pt-ITO was studied. The results of LSV tests indicated that Cl2 generation of Pt-ITO locates at 1.1V, which is reduced by 0.4V compared with the pure ITO. The optimal electro-catalytic property parameters are determined as applied current density of 0.05 m A/cm2 with deposition time of 1800 s. The anodic oxidation current of chlorination can reach 5.5m A/cm2 when the potential is 1.5V.(3) The longevity and sustainability of electrochemical chlorination in 3.5% Na Cl solution and natural seawater were compared between pure ITO and Pt-ITO. The electro-catalytic property before and after electrolysis was evaluated by the DC electrolysis and LSV technique. The results indicated that the final oxidation current density of pure ITO are both reduced to zero and Pt-ITO can still reach 2.8m A/cm2 and 2m A/cm2 when the potential is 1.5V in both solution. The longevity and sustainability of Pt-ITO electrode is obviously better than pure ITO electrode.(4) The fouling state on the substrate surface of slide glass, pure ITO and Pt-ITO immersed in diatom solution for 5, 10 and 15 days was detected by means of optical microscope. The study showed that quite heavy fouling biomass has been accumulated on the surface of slide glass and bare ITO. In contrast, Pt-ITO with in situ Cl2 generation has prevented the diatom organism from adhering and growing. Therefore, the biofouling on its surface is the slightest one.In this issue, Pt-ITO novel composite electrodes were successfully prepared with the electrochemical deposition technique. The anodic potential of electrolysis seawater is reduced, and the oxidation current density as well as sustainability of working electrode is improved. It provides a new choice of working electrode used for chlorination on underwater optical window. It is important for anti-biofouling of underwater optical devices to reduce energy consumption and acquire high-quality scientific data.