Studying On The Modification RuO₂-TiO₂Oxide Coating Catalyst With Chlorine Evolution And Oxygen Evolution Reaction

Anodes coated by the thin film of active oxides on titanium supports（dimensionally stable anodes, called DSA） are widely used in the fields of chlor-alkaliindustry, water electrolysis, wastewater treatment, electroplating industry and cathodicprotection, due to their high corrosion resistance, superior conductibility andelectro-catalytic activity for chlorine evolution reaction （CER）. However, for oxygenevolution reaction （OER） in water electrolysis, research has still been focused on theexploitation of electrode materials with low anodic overpotential since OER on ananode causes the major energy loss. For chlor-alkali industry, the anodic overpotentialsof CER increase with the reaction progressing, owing to the oxide coatings flaked offand active species dissolved, which induce the reduction of active site of the electrodesurface for DSA. When the potential of CER is close to that of OER, it is found to thatthe efficiency of chlorine gas production reduce and OER increase gradually, whichfacilitate to form passivation film （TiO₂） between Ti substrate and oxide coating,resulting in the electrode deactivation. Hence, it is still a great challenge to design andprepare DSA with high catalytic activity and stability for water electrolysis andchlor-alkali industry. Based upon the above problems, in present work, the OER andCER catalysts are prepared for using in different electrolytes, while their catalyticperformation and mechanism are also studied.（1） The OER catalysts based on RuO₂-TiO₂-PbO₂oxide coatings have beenperpared by thermal decomposition method. The nanostructure, surface morphology,chemical composition and catalytic activity were investigated.â‘ The experimentalresults show that the surface morphology of RuO₂-TiO₂-PbO₂electrode is greatlyinfluenced after the oxide coatings were doped with PbO₂. The addition of a smallamount of PbO₂improves the catalyst activity, since the phenomenon of aggregation isreduced and the real surface area increases. However, the high content of PbO₂additionexhibits opposite trend. This low catalyst activity is attributed to forming passivationfilm （TiO₂） between Ti substrate and oxide coating, resulting in the electrodedeactivation. Therefore, the appropriate amount of PbO₂addition could promote theactivity and stability of DSA.â‘¡The thermal decomposition temperatures are alsostudied and apparently affect the electrode surface morphology and catalytic activity.The catalyst prepared by thermal decomposition at450℃displayed the highest activity among the catalysts studied.（2） TNTs arrays have been prepared by anodization of Ti substrate. AndRuO₂-TiO₂/TNTs catalysts are obtained by thermal decomposition method. Theperformance of prepared catalysts towards CER was examined by polarizationmeasurements in5.39M NaCl solution. The main results are as follows:â‘ Comparedwith the pure Ti substrate, TNTs arrays have large surface area, which is helpful forRuO₂-TiO₂/TNTs electrode to increase the catalytic activity.â‘¡As TNTs arrays arecalcined at475℃, RuO₂-TiO₂/TNTs electrodes prepared by thermal decomposition at450℃and500℃reveal different catalytic activity and stability. Compared with the450℃, when the thermal decomposition temperature is500℃, RuO₂, TiO₂and TiO₂in TNTs arrays could reform to crystallology structure, which not only increasecatalytic activity of electrode, but also improve the interaction between the active oxidecoating and TNTs arrays, and thus promoting the stability of electrode.