Fabrications Of Self-supporting Electrodes Based On Titanium Dioxide Nanotube Arrays For Advanced Electrocatalytic Applications

One-dimensional nanomaterials possess merits such as direct electron/ion transportation pathway,strong stress tolerance,and short axial electron ion transmission paths.Electrocatalysts based on one-dimensional nanomaterials have been extensively investigated.However,many powdery nanomaterials need to be casted on the current collector by mixing polymeric binder,which inevitably increases the resistance and may bury the active sites.Self-supporting electrode with nanostructure in situ grown on the conductive substrate does not require binder,thus resulting a direct channel for electron transport and high stability of the electrode.In this thesis,nanotube arrays with a one-dimensional structure were prepared on titanium substrate to load electroactive nanomaterials.The prepared self-supporting electrode exhibits excellent catalytic activity and stability for hydrogen evolution and electrocatalytic chlorine evolution.The main research contents are as follows:（1）Highly ordered one-dimensional TiO₂ nanotube arrays（TiO₂ NTAs）were prepared on the surface of the titanium substrate by electrochemical anodization.Mo₂C nanoparticles were loaded on the nanotubes by the oxidation-reduction reaction of phosphomolybdic acid and pyrrole.By introducing a Pt counter electrode in electrochemical cycling,trace Pt species were dissolved and redeposited on the working electrode composed of Mo₂C nanoparticles anchored on the inner wall of TiO₂ NTAs.Pt species were embedded in the crystal defects of Mo₂C nanostructures with high dispersion and ultra-low Pt loading of～13μg cm^-2.The as-prepared Pt-Mo₂C/TiO₂NTAs exhibit highly electrocatalytic activities towards hydrogen evolution with an overpotential of 67 mV at the current density of 10 mA cm^-2 and a Tafel slope of 39.3mV dec^-1.The mass activity of Pt-Mo₂C/TiO₂ NTAs is about 8-folds greater than that of commercial Pt/C electrode.Excellent stability has also been demonstrated.（2）Ru and Ir were loaded on the anodized TiO₂ NTAs by electrodeposition.After thermal annealing in air,self-supporting RuO₂/IrO₂-TiO₂ NTAs electrode was fabricated.The initial potential is 1.05 V vs.SCE in 5 M NaCl solution.At a current density of 50mA cm^-2,the overpotential is 1.12 V vs.SCE and the Tafel slope is 34.1 mV dec^-1.The catalytic performance is superior to most chlorine evolution catalysts.The chlorine evolution activity was almost unchanged after test at the current density of 50 mA cm^-2for 12 h,indicating the excellent stability of RuO₂/IrO₂-TiO₂ NTAs.In addition,the interference of the oxygen evolution reaction was evalutated in a 0.5 M H₂SO₄ solution.At a current density of 50 mA cm^-2,the potential gap between the chlorine evolution and the oxygen evolution is 205 mV,indicating good selectivity to the chlorine evolution reaction by inhibiting the oxygen evolution reaction.The excellent electrocatalytic chlorine evolution activity and selectivity should be attributed to the high specific surface area of the one-dimensional nanotube arrays and the synergistic effect of RuO₂ and IrO₂.