The Preparation And Electrochemical Oxidation Performance Of Hierarchically Nanostructured And Palladium-loaded Blue TiO₂

Blue TiO₂ is considered as a promising anode material for electrochemical degradation of organic pollutants due to the excellent electro-catalytic activity.However,the electro-catalytic activity is subject to morphological structure and interfacial properties of Blue TiO₂.In this work,the Blue TiO₂ with a hierarchical nanostructure of nanoparticles,a porous layer,and nanotube arrays piled in sequence was prepared by anodization in ice-water bath and cathodic reduction.Furthermore,the palladium loaded Blue TiO₂（Blue TiO₂-Pd）was prepared via cyclic voltammetry electrodeposition and in-situ reduction by Blue TiO₂substate.The corresponding electrochemical oxidation performance and stability of Blue TiO₂ and Blue TiO₂-Pd were studied:（1）Compared to anodization without ice-water bath,anodization in ice-water bath did not change the oxygen evolution potential（2.5 V vs.Ag/Ag Cl）of Blue TiO₂,but it increased Ti³⁺possession by 20%,electrochemical active area by 70%,and reduced internal resistance by 73%;the kinetic rate of methylene blue degradation was increased by 40%,and the chemical oxygen demand（COD）of real wastewater was completely removed by 18 k Wh/kg COD less energy consumption,the accelerated life time was 1.4 times increased.These results indicated the hierarchical nanostructure TiO₂ prepared via anodization in ice-water bath enhanced the electron transport capacity of the electrode by increasing the Ti³⁺self-doping efficiency,thereby improving the electrochemical oxidation performance and stability of Blue TiO₂.（2）Blue TiO₂ could produce hydroxyl radicals and sulfate radicals in the electrolyte containing Na₂SO₄,while the electrochemical degradation performance of Blue TiO₂ mainly relied on hydroxyl radicals.Sulfate radicals could contribute a great deal under the high concentration of Na₂SO₄,low current density,and high initial p H.（3）Blue TiO₂-Pd was prepared via cyclic voltammetry electrodeposition and in-situ reduction by Blue TiO₂substate to adjust the electronic structure of the electrode surface and therefore maintain Ti³⁺-oxygen vacancies in Blue TiO₂.Although compared to Blue TiO₂,the Ti³⁺possession of Blue TiO₂-Pd was decreased by 10.6%and oxygen evolution potential was decreased to 2.2 V（vs.Ag/Ag Cl）,the electrochemical active area was increased by 65%,internal resistance was reduced by50%;the kinetic rate constant of methylene blue degradation was doubled,and the COD of real wastewater was completely removed by 22 k Wh/kg COD less energy cosumption.The free radical quenching test showed that the excellent degradation performance of Blue TiO₂-Pd could be attributed to the enhanced ability of Blue TiO₂to generate hydroxyl radicals.（4）The accelerated life of Blue TiO₂-Pd（10350 min,20 m A/cm²）was about 10times that of Blue TiO₂,and the morphology slightly damaged after accelerated life time test,suggesting the Ti³⁺-oxygen vacancies and nanostructure were very stable.The enhanced electrochemical oxidation performance and stability of Blue TiO₂-Pd were attributed to the strong interaction between Pd and the Blue TiO₂ substrate,which improved the electron transport capability of the electrode.