Development Of Co-based Catalysts Used To Generate Chlorine And Research On Application For Anti-fouling Of Ocean Optical Windows

Optical sensors are significant for long-term in situ monitoring of marine environments,but they will suffer biofouling in their service,which seriously affects the detection accuracy.Several methods have been adopted to protect optical windows against biofouling,and the electrochemical chlorination method has gained numerous attention due to its easy operation and high efficiency.Meanwhile,the amount of chlorine biocide is controlled to the minimum required to prevent biological contamination without harmful effects on the marine environment.However,the two main problems ought to be focused to develop the electrochemical chlorination systems for antifouling of optical windows:efficient catalysts with low cost for chlorine evolution reaction(CER)in seawater and the guarantee of underwater optical transmittance.Hence,in the work,Co-based catalysts were prepared by potentiostatic electrodeposition and thermal decomposition method,which reduced the fabrication cost of working electrode,and improved efficiency for CER and longevity of working electrode.Besides,good antifouling of optical lens in seawater was achieved by a designed electrochemical chlorination accessory equipped with the as-prepared catalyst electrode.The specific research works are listed as follows:(1)Co-based catalyst electrodes composed of Co and Co(OH)₂ was prepared by a potentiostatic electrochemical technique,and its optimal deposition potential and time were determined.The results of tests indicated that as-prepared electrode exhibited significantly better selectivity for CER than commercial DSA.CER mainly occurred at the potential of 1.1 V-1.4 V and the current efficiency always kept above 80%at the current density range of 1-20 m A/cm~2 in 0.6 M Na Cl solution.Moreover,the Cl₂generation performance of electrode showed little decay after stability tests of 10 h at the current density of 5 m A/cm~2.(2)The bactericidal tests against P.aeruginosa and S.aureus showed that active chlorine produced by electrolysis of seawater through working electrode exhibited high-efficient and broad-spectrum bactericidal properties.After immersion of 15 days in seawater solution containing bacteria,there was little biofouling and maintained higher underwater light transmission for the protected optical glass by periodic electrochemical chlorine evolution compared to the optical window without any protection,and the results of fluorescence microscopy showed that only a small number of bacteria were attached on the protected glass.Meanwhile,it was known from 3D laser confocal microscopy observations that Cl₂ generation by electrolysis of seawater can inhibit the accumulation of organic macromolecules on optical glasses,thereby retarding bacterial sedimentation.(3)The optimum pyrolysis temperature was 400?for the preparation of Co-based catalyst electrode by thermal decomposition method.The electrocatalytic properties of the electrode for CER can be further improved by Both the doping of a certain proportion of Ni atoms and the addition of an Sn Sb interlayer.The immersion test of 15 days with bacterial solution showed that the electrode prepared by thermal decomposition with in situ electrochemical chlorination was able to effectively inhibit the attachment of bacterial organisms on optical glass and prevent biofouling.In the work,Co-based catalyst electrodes were successfully prepared by potentiostatic electrochemical and thermal decomposition method,which reduced the fabrication cost of electrode,improved efficiency as well as the working stability for CER.The designed device without sacrificing light transmittance effectively suppressed biofouling of the underwater optical glass by in situ electrochemical chlorination.The study has important implications for the long working time of underwater optical instruments.