| With the increasing development of cities and industries,water pollution problem has become one of factors to restrain the developments of modern economics and society.Electrocatalytic oxidation technology has played an increasingly prominent role in treating refractory wastewater,and has been considered to be one of the most promising water treatment technologies.Electrode materials have been the key,and their performance has been in direct relation to the electrocatalytic oxidation technology.Sb-doped SnO2 electrode has been well known for its low cost,high oxygen evolution potential and electro-generation of hydroxyl radicals.Higher oxygen evolution potential can restrain the subsidiary reaction of oxygen evolution,and hydroxyl radicals can effectively suppress the electrode fouling and restore electrode activity.Consequently,Sb-doped SnO2 electrode is one of the most promising electrodes for the electrochemical oxidation of organic pollutants.Electrodeposition methods were used to prepare Ti/Sb-SnO2 composite electrodes,and various deposition modes were performed to design and conduct the microstructures of composite electrodes.Effects of deposition modes were investigated,and interactions between the layer composition and the micro structure were studied.Ti/Sb-SnO2 electrode was prepared by the pulse electro-codeposition method and was modified with titanium nitride nanoparticles.X-ray photoelectron spectroscopy analysis showed that introducing titanium nitride nanoparticles facilitates the formation of Sb5+.And the adsorbed hydroxyl oxygen species content of Ti/Sb-SnO2-TiN(43.1%)is higher than that of Ti/Sb-SnO2(21.9%),indicating that Ti/Sb-SnO2-TiN electrode has more active sites for electrochemical oxidation of organic pollutants.The dye decolorization results also confirmed that Ti/Sb-SnO2-TiN electrode has higher decolorization efficiency and kinetic rate constant,which are 1.5 and 3.2 times as efficient as those of Ti/Sb-SnO2,respectively.The effects of nano-CeO2/Ce ion doping Sb-SnO2 electrode were investigated.The results showed that effects of nano-CeO2 doping and cerium ion doping are quite different.Nano-CeO2 doping mitigates the surface antimony enrichment and promotes the complete oxidation of antimony so that the major antimony oxidation states exist as Sb5+ state,while cerium ion doping aggravates the enrichment and increases the Sb3+ content.Compositional gradient electrode of Ru-Sb-SnO2 was fabricated by the selective potential-pulse electrodeposition method.Applying the selected three-step potential pulse,a uniform layer with controllable composition gradient was obtained and had morphology of vertically aligned sheets.The Ru content in the deposition layer displays a parabolic variation and has a maximum value of 2.4 at.%with 200 deposition cycles.The electrocatalytic dye decolorization experiments showed that first-order kinetics constants on Ti/Ru-Sb-SnO2 electrode reaches 23.0×10-3/min(for metylene blue),25.1×10-3/min(for orange ?)and25.2×10-3/min(for methyl orange),respectively.These results demonstrated that the compositional gradient electrode possesses a great catalytic activity and wide use for dye decolorization.Gradient Pd-Sb-SnO2 electrode was also presented.Scanning electron microscopy results showed that selectively deposited electrodes possess the morphology of flower-like clusters.The discussion for growth mechanism demonstrated that the production of flower-like cluster is related to the diffusion limitation.Selectively deposited electrode possesses higher Sb5+/Sb3+ ratio and higher Oads/Olat ratio.And electrochemical characterization showed that selectively deposited electrode has a significantly enhanced electrochemcial activity(98.57 ohm versus 362.7 ohm).First-order kinetics constants of dye decolorization processes on selectively deposited electrode are larger(24.2×10-3/min for methylene blue,39.7x10-3/min for orange ? and 51.7×10-3/min for methyl orange,respectively).These results demonstrated that the selectively electrodeposited electrode possesses efficient catalytic activity.Multi-step pulse electrodeposition method was used to construct the multilevel Sb-SnO2@TiO2-NTs electrodes.Through modulating pulse signals,various morphologies were realized,including the flower-like structure,the hierarchical structure of sheets and the leaf-like structure.The electrocatlytic methyl orange decolorization results showed that the first-order kinetics constants of flower-like electrode,hierarchical electrode and leaf-like electrode are 32.5×10-3/min,39.7×10-3/min and 51.7×10-3/min.A facile method was used to successfully fabricate the three-dimensional macroporous foam architecture of CNT-SnO2 electrode that possesses the same framework as the kitchen low-cost macroporous sponges.This 3D CNT-SnO2 composite presents a clear micro-structure of CNT inside and amorphous SnO2 nanoparticles coating around the CNT surface,and has an integration of electricity generation and energy storage in MFCs.Compared with CNT electrode,CNT-SnO2 electrode presents a much higher output current density(2.21 versus 0.47 mA/cm2),power density(673.5 versus 443.1 mW/m2)and specific capacitance(382 versus 42.8 mF/cm2).These results revealed that 3D CNT-SnO2 composite has a great promise as the anode material for MFCs. |
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